A complete guide to the repair, cleaning, and adjustment of binoculars-for the hobbyist as well as for the advanced technician. I I I I I I I I I I I I I
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By: Alii Service Notes
Includes-optical & mechanical operation -disassembly -cleaning -lubrication -repairs -collimation and other adjustments -zoom binoculars
Repairing & Adjusting Binoculars By Alii Service Notes Copyright ©1996 by Alii Service Notes.
Other books by Alii Service Notes:
Camera Care Camera Technician's Guide Parts and Information Directory Restoring Classic and Antique Cameras
Canon Camera Repair Notes Minolta Camera Repair Notes Nikon Camera Repair Notes Pentax Camera Repair Notes
Repair and adjust binoculars!
Repair your own binoculars. Or add binocular repair to your business. Here's how to restore binoculars to proper working condition-including:
o o
o o o o o
basics of binoculars-optical and mechanical operation. the tools you need to repair binoculars. cleaning optics. lubrication. how to disassemble binoculars-and how to avoid disturbing adjustments. adjustments-collimation, rotational error, diopter setting. zoom binoculars-how they work and how to adjust them.
Fully illustrated with over 150 drawings and photos.
Contents: Introduction How to use this book
37
Section A-Binocular basics Power of Binoculars Optical Principle of Binoculars Variations in the Basic Design Other Types of Prisms Quality Differences in Binoculars & Repair Techniques Section B-Disassembly Tools for Disassembly Cleaning Binocular Optics Cleaning Metal Parts Lubrication Disassembly Techniques Objective-lens parts Removing the prism covers Removing the ocular assembly from a rocker-arm design Removing the ocular assembly from a focus-knob design Porro prisms, prism shelves Disassembly and adjustment of the oculars Variations in Oculars
Disassembly of Opera Glasses Reassembly of Opera Glasses Summary of Disassembly Rules and Precautions Section C-Adjusting Collimation
Binoculars
Checking Collimation Objective-Lens Adjustments Eyelens Adjustments Porro-Prism Adjustments Adjusting Rotational Error with the Porro Prisms Adjusting the Porro Prism for Collimation Prism-Shelf Adjustments Adjusting Focus Other Adjustments Summary of Optical Adjustments Section D-Zoom Binoculars Operation of the Zoom Lens Disassembly of the Oculars Other Coupling Systems Removing the Ocular Tubes Checking Ocular Timing Other Types of Zoom Binoculars Index
2 18 55 60 35 46 45 3 68 54 20 21 36 31 30 48 47 17 16 7 37 15 24 22 34 950 67 65 53 26 25 55 42 4 18 69
•
1
INTRODUCTION Since starting AliiSome Service Notes, we'vetohad many for a book on binocular repair. people just want repair theirrequests own binoculars. Others want to add binoculars to their present repair line. We've tried to design this book for both needs as well as for the needs of experienced binocular-repair technicians. The text materials don't provide step-by-step coverage of every type of binocular; we concentrate on the conventional porro-prism binoculars, the type you'll most frequently encounter. However, the theory behind the repair and adjustments applies to other types of binoculars as well.
Binocular or binoculars? You'll see binocular, describing a single unit, written both in the singular and in the plural-a binocular or a pair of binoculars. The binocular consists of two halves that are practically mirror images of one another. Either the singular or the plural is acceptable.
Where to get parts and tools for binocular repair. Most of the tools you need for binocular repair are standard tools available from a variety of sources. At the bottom of this page, we've listed four sources for small tools and special lubricants. Each of these sources provides a complete catalog. Parts and specialized tools present a different problem. If a binocular needs parts, the repair may not be economical-at least for an inexpensive pair of binoculars. However, a good pair of binoculars may justify the parts costs. The only parts source is the manufacturer of the binoculars. Most of the specialized tools described in this book also come from manufacturers of binoculars. The addresses and phone numbers of binocular manufacturers are listed in another Alii publication-the Parts and Information Directory.
Sources of Tools & Lubricants
2
Alii Service Notes
Fargo Enterprise
P.O. Box 30871 Honolulu, HI 96820 phone: (808) 848-0029 fax: (808) 848-0691
P.O. Box 6505 Vacaville, CA 95696 phone: (707) 446-1120 fax: (800) 249-3182
Cam-Comp, Inc
Vivitar Corporation
325 Route 17M, Suite 5 Monroe, NY 10950 phone: (914) 782-4248 fax: (800) 735-3319
1280 Rancho Conejo Blvd. Newbury Park, CA 91319 phone: (800) 421-2381 fax: (805) 498-5086
HOW TO USE THIS BOOK
If
you'reThere neware to four binocular you with can the use basics this book as a self-study program. sectionsrepair, that start and proceed progressively to more complex subjects.
The first section-Section A-provides background information on binoculars. Here you gain the background you'll need before taking apart a pair of binoculars for the first time. Section A also provides the terminology used in the remaining sections. Section B starts with information on tools and techniques. You first learn about the special tools that are needed for repairing binoculars. You also learn how to clean the optics and what lubrications to use on the mechanical parts. The rest of Section B covers disassembly techniques. You'll find that this material is much easier to understand if you have a pair of binoculars to disassemble. Ideally, you should start with a "junk" pair of binoculars. Learn the basics-and how to avoid disturbing adjustments-before you tackle customers' binoculars. Garage sales and flea markets sometimes provide a source for inexpensive binoculars you can use as practice equipment. Or check with businesses that often do binocular repair, such as camera-repair shops. Such shops may have binoculars that were "donated" by customers who didn't want to pay the charge for repairs. Section C covers the optical adjustments. If you have some background in binoculars-and you just want to adjust a pair of binoculars-you may be able to skip directly to this section. Again, if you're new to the field, it helps to have a pair of binoculars you can use when following the instructions in Section C. Try throwing out the adjusunems. And then make the adjustments on your practice binoculars. Section D covers the oculars (eyepiece assemblies) in zoom binoculars. You probably should not attempt repairs on zoom binoculars until you're proficient in the first three sections. Zoom binoculars just add variable magnification to the principles already covered.
3
SECTION A-BINOCULAR TheButword binocular to viewingbetween with both eyes. there's more ofrefers a difference binoculars and telescopes than the viewing method. In this section, we'll take a look at those differences along with the basic optical principles governing binoculars. Fig. Al shows the terminology we'll be using in this book. The large lenses at the front of the binoculars are the objective lenses. These lenses gather the light from the image and bring that light to a focus point inside the binoculars. The eyepiece assemblies-the oculars-magnify the images formed by the objective lenses. The ocular is the complete eyepiece assembly. It consists of the eyelens (the lens closest to your eye) as well as the other lenses in the eyepiece. Many binoculars have rubber eyecups at the ends of the oculars. If you wear eyeglasses, you can roll up the rubber eyecups. One side of the binoculars is hinged to the other side. Each side of the binocular pair mounts to the hinge pin. The hinge allows you to change the separation between the binocular sides to match the distance between your eyes. You simply spread the sides further apart-Dr move the sides closer together-until the dis-
DECORATOR
/
CAP
OBJECTIVE
BASICS
tance between the eyelenses matches the distance between your eyes. The distance between the eyelenses is the interpupillary distance (the distance between the pupils of your eyes). Many binoculars include a scale-the IPD scale-- for setting the interpupillary distance, Fig. A2. The IPD scale shown in Fig. A2 is on a disc attached to the hinge pin-the index is on one of the ocular arms. If you remember your own interpupillary distance, you can quickly set the binoculars by referring to the IPD scale. The calibrations on the IPD scale are usually in millimeters. For example, spread the binocular sides until the index aligns with "70." The distance between the centers of the eyelenses is now 70mm. Practically all binoculars have two focus adjustments for matching the binoculars to your own eyes and to the subject distance. A common design uses a focus knob, Fig. AI, that moves both oculars simultaneously. The oculars move in out along a threaded shaft-closer to the binocular body or further from the binocular body. But your two eyes probably don't have identical cor-
LENSES
OBJECTIVELENS TUBE
FRONT PRISM COVER
BODY FOCUS KNOB HINGE PIN
REAR PRISM COVER OCULAR
ARMS
EYECUP
FIG. A 1 The common terms for the parts of binoculars. 4/BINOCULAR BASICS
ADJUSTABLE
OCULAR
(PO SCALE
FIG. A2 Many binoculars have a scale to show the interpupillary distance (IPO). This scale is calibrated in millimeters.
rections-that's why one of the two oculars is adjustable, Fig. A3. Turning the control knob moves the adjustable ocular along screw threads. The adjustable ocular then moves in or out, allowing individual correction. With most binoculars, the adjustable ocular is the righthand ocular-the ocular you look through with your right eye. Focus the binoculars by using the focus knob to adjust the focus through the fixed ocular. Then adjust the adjustable ocular. For example, consider that the right-hand ocular is the adjustable ocular. First close your right eye. Turn the focus knob until the image seen through the left side appears sharp. Then close your left eye and open your right eye. Turn the diopter control until the image seen through the right side appears sharp. You've just focused the oculars according to the subject distance and to your own eyesight. The adjustable underside, Fig. correction. You steps correction
ocular is normally calibrated on the A3. The 0 on the scale indicates no can turn the control knob to set up to 3 in either direction.
CONTROL
KNOB
DIOPTER SCALE
FIG. A3 The diopter scale is usually on the bottom of the right-side ocular. Typically the adjustable ocular allows a correction of :t3 diopters.
ROCKER ARM
Although you will encounter variations in the scales, the calibrations are normally quite close from one pair of binoculars to another. The steps of correction are based on diopters-units of correction for individual eyesight. The index is on the ocular arm. If you remember the correction you need, you can preset the adjustable ocular. Then turn only the focus knob to focus the binoculars. In some binoculars, the focus control is at the center of the hinge pin-between the sides ofthe binoculars. The design shown in Fig. A4 uses a rocker arm as the focus
OCULARS
FIG. A4 The rocker arm moves both oculars simultaneously. BINOCULAR BASICS/S
control. Push one side of the rocker arm to move the oculars in one direction; push the other side of the rocker arm to move the oculars in the opposite direction.
SCREW ON HINGE PIN
A
In Fig. A4, a carn slot rather than a threaded shaft moves the oculars. The carn slot is in the rocker arm, Fig. AS. A screw on the hinge pin rides in the cam slot. Pushing the left -hand side of the rocker arm moves the cam slot as shown in Fig. AS (B). The carn slot then drives the ocular assembly toward the front of the binoculars. If you push the right -hand side of the rocker arm, the cam slot moves as shown in Fig. A5 (C). The ocular assembly now moves toward the back of the binoculars.
B You normally can't see the cam slot in the rocker armit's covered by a decorator cap, Fig. A6 . The decorator cap just snaps into place. In Fig. A6, we've removed the ocular assembly from a pair of binoculars with a rocker-arm focus control. The ocular assembly-the two ocular arms with the oculars-mounts to the hinge pin, Fig. A6. As you
C
FIG. AS The cam slot is part of the rocker arm. A screw on the hinge pin rides in the cam slot.
DECORATOR PLATE
\
move the rocker arm, the hinge pin moves toward the front or toward the back of the binoculars. The hinge pin carries the ocular assembly in the same direction. To see the cam slot and the screw on the hinge pin, remove the snap-fit decorator plate, Fig. A6. Fig. A7 shows the rocker arm with the decorator plate removed. You've seen that the rocker mm moves the complete hinge pin to adjust the focus. By contrast, the focus knob of the binoculars shown in Fig. Al moves only the shaft that carries the ocular assembly. The ocular arms fit over the shoulder of the ocular shaft, Fig. A8.
HINGE PIN
FIG. A6 Binoculars with the ocular assembly removed. The rocker arm moves the hinge pin in or out. The hinge pin carries the ocular assembly. 6/BINOCULAR BASICS
The ocular shaft screws into the focus knob, Fig. A8. And the focus knob screws into the hinge pin. But only the focus knob can rotate-the oculm' arms prevent the ocular shaft from rotating with the focus knob. Since the ocular shaft can't rotate, it moves in or out along its screw threads. The ocular shaft then carries the ocular assembly in the sarne direction.
Some binoculars-such as military binoculars-eliminate the control that moves the two oculars simultaneously. Both oculars are individually adjustable, Fig. A9. You must adjust each ocular individually for your own eyesight. Each ocular has diopter calibrations simi1ar to the calibrations shown in Fig. A3.
SCREW ON HINGE PIN
POWER OF BINOCULARS Binoculars are rated according to the magnification and to the diameter of the objective lenses. Increasing the diameter of the objective lenses increases the light-gathering ability. So, in low-light situations, the larger objective lenses do a better job by gathering more of the existing light. Most binocular objectives are either 30mm in diameter or 50mm in diameter. The term night glasses refers to binoculars with 50mm objective lenses. The larger objective lenses are better suited for use at night. You'll see a pair of numbers on the binoculars that indicate both the magnification of the oculars and the diameter of the objective lens-such as 7 x 30. The 7x is the magnification of the oculars-the oculars magnify the image formed by the objectives 7 times. The second number - 30--tells you that the diameter of each objective lens is 30mm.
/
FIG. A7 Removing the decorator plate from the rocker arm (see Fig. A6) uncovers the hinge-pin screw and the cam slot.
HINGEPIN
SCREW THREADS OF OCULAR SHAFT
SCREW THREADS OF !
FOCUS KNOB FOCUS KNOB
ADJUSTABLE
OCULARS
SHOULDER OF OCULAR SHAFT
FIG. A8 With a focus-knob system, the ocular assembly mounts to the shoulder of the ocular shaft.
FIG. A9 In some binoculars, both oculars are individually adjustable. There's no control to move the oculars simultaneously. BINOCULAR BASICSn
The power and the cliameter of the objective lenses also tell you the diameter of the exit pupil-the actual image area. To see the exit pupils, look through the binoculars at an illuminated source-perhaps the sky. Now hold the binoculars around 6" from your eyes. The illuminated circles you can see at the centers of the eyelenses, Fig. Al 0, are the exit pupils. Determine the diameter of the exit pupils by the formula: exit pupil = diameter of objective lens power Zoom binoculars, Fig. All, allow you to change the power-the actual magnification of the oculars. The zoom binoculars have a control that shifts the internal ocular optics to change the magnification. The optical principle is similar to that used in zoom lenses for cameras. As you move the zoom lever, Fig. All, a magnification scale shows you the actual setting, Fig. A12.
FIG. A10 The power and the diameter of the Objective lenses is normally marked on a cover plate next to one ocular. In this example, the magnification is 7 power. The diameter of each objective lens is 50mm.
The zoom binoculars shown in Fig. All are calibrated 7X-15X35. The calibrations 7X-15X show that the oculars can then be changed in magnification between 7 power and 15 power. In this example, the diameter of each objective lens is 35mm.
INDEX
ZOOM LEVER
FIG. A 11 Zoom binoculars allow you to change the magnification of the oculars. 8/BINOCULAR BASICS
FIG. A 12 The numbers under this zoom ocular indicate the selected magnification. The index ring rotates as you move the zoom lever. In this example, the magnification is between 9 and 10 power.
OPTICAL PRINCIPLES OF BINOCULARS The optical principles of binoculars are similar to the principles of another sighting instrument, the telescope, Fig. A13. With the telescope, the objective lens gathers the light and forms an image inside the telescope, Fig. A14. The image formed by the objective lens is called a virtual image-it exists in space rather than being projected onto a surface such as a movie screen or another optical surface. An image projected onto a surface is, by contrast, a real image. If you could place such a surface behind the objective lens, the virtual image would become a real image-one that you could see. For example, say you're looking inside the telescope-directly at the image formed by the objective lens. You won't see the virtual image. But, if you place a ground glass or a focusing screen at the focal point of the objective lens, you will see the image.
FIG. A13 The telescope, a close relative of binoculars.
I POSITION
OF
FOCAL POINT OF OCULAR
:
VIRTUAL IMAGE
I
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INCOMING LIGHT RAYS
I
FOCAL LENGTH OF OCULAR
FOCALPOINT OF/ OBJECTIVE ¢>
LENS
FOCAL LENGTH OF OBJECTIVE
LENS
EYELENS
¢
FIG. A14
LIGHT RAY
To bend the light rays as shown in Fig. A14, the objective lens relies on the optical principle of refraction. Refraction is the bending of the light rays as the light passes from a medium of one density to a medium of a different density. With the lens, the light passes from air (low density) into the glass of the lens (high density). The glass then slows down the light ray. Because of the curvature of the lens, one side ofthe light ray slows down before the other side slows down. For example, consider the light ray entering the lens in Fig. A15. Because of the curvature of the lens, the bottom edge of the light ray slows down before the top edge slows down. As a result, the light ray bends down.
FIG. A15 The curvature of the glass and the density of the glass determine how much the light ray bends (refracts). BINOCULAR BASICS/9
But when the light ray leaves the lens in Fig. A15, the top edge of the light ray enters the air first. The light ray speeds up when it enters the air. Since the top of the light ray speeds up before the bottom of the light ray, the light ray bends up. The amount the light ray refracts depends on two factors: the curvature of the lens and the density of the glass. Increasing the curvature of the lens causes the light ray to bend more. The more dense the glass, the more the light ray bends-the denser medium slows down the light ray a greater amount. If the subject is at infinity (an infinite distance from the lens), the incoming light rays are parallel to one another, Fig. A14. The objective lens brings the light rays to a focus point. The distance between the optical center of the objective lens and the focal point when the subject is at an infinite distance is the focal length of the lens. You can optically simulate a target at an infinite distance-you'll see one method in Section C (Adjusting Binoculars). But for test purposes, you can consider a target at a distance of around two miles to be infinity. In Fig. A14, the subject is a point source of light. A normal scene, however, is made up of many point sources coming from different directions. In Fig. A16,
we've added two more point sources from the subject after passing through the objective lens. Now the objective lens brings the point sources to a plane-the focal plane. The focal point of the ocular, Fig. A14, is at the same place as the focal point of the objective lens. The ocular magnifies the virtual image and forms a real image-an image you can see by looking through the ocular. As with binoculars, you can move the ocular in or out to correct for your own eyesight. If the subject is at a focus distance closer than infinity, the incoming light rays are no longer parallel-rather, the light rays diverge from the subject. The objective lens brings together the light rays at a point behind the focal point in Fig. A14. As a result, the virtual image is formed closer to the ocular. You must then move back the ocular-further from the objectiveto bring the image into sharp focus. The telescope shown in Fig. A14 is an aerial telescope, used for viewing such things as stars and planets. The image appears inverted (upside down) and reverted (reversed from left to right)-a positive lens (a lens that focuses the light rays at a point behind the lens as shown in Fig. A14) always inverts and reverts the image. The subject rays coming from the bottom of the lens are focused at the top of the focal plane, Fig. A16.
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FIG. A 16 All the image points from the subject are focused at the focal plane. 1O/BINOCULAR
BASICS
LENS-ERECTING
SYSTEM
FIG. A17 With a terrestrial telescope, the image passes through an erecting system. The image you view is right side up and correctly oriented from right to left. To make the image appear right side up, it's necessary to add more optics-an erecting system. The erecting system erects the image. In Fig. AI?, we've added a lens- erecting system to the telescope. The lens-erecting system inverts and reverts the image once morenow the image appears right side up and correctly oriented from right to left. The telescope is now called a terrestrial telescope-a telescope used to view objects on the earth rather than in outer space.
INTEROBJECTIVE
DISTANCE
INTERPUPILLARY
DISTANCE
If you attached two of the telescopes shown in Fig. AI? side by side, you could use both your eyes to view the subject. But you still would not have a typical pair of binoculars. With most binoculars, the objective lenses are spaced further apart than the oculars. The increased space between the objective lenses results in a greater 3-dimensional effect. When you look at an object, each of your eyes sees the object from a slightly different angle. As a result, you get a 3-dimensional view. If you close one eye, you'll find that your view has suddenly become 2 dimensional. You see height and width. But the object appears to have no depth- it's flat, like the picture in a magazine.
FIG. A 18
The binoculars increase the 3-dimensional effect by placing the objectives further apart than the eyelenses. Each objective lens sees the same subject. But the two objective lenses see the subject from different angles. The distance between the objectives is called the interobjective distance-that's the distance measured from the center of one objective to the center of the other objective, Fig. AI8. The distance between the eyelenses, as mentioned earlier, is called the interpupillary distance. To move the objectives further apart than the ocularsas well as to shorten the overall length of the binocular-each binocular side displaces the light. The light travels in the path shown in Fig. A19. Prisms do the job of displacing the light and shortening the required length of the light path.
FIG. A 19 The light path inside the binoculars.
BINOCULAR BASICS/11
A prism is a piece of optical glass designed to reflect light rays. There are different types of prisms distinguished by their shape or by the manner in which they reflect the light rays. For example, a 90· prism, Fig. A20, reflects the light at a 90° angle. A 90° prism is also called a right-angle prism-both for the shape and for the direction that the prism reflects the light (a right angle).
RIGHT ANGLE
Fig. A21 shows the light path through the 90° prism. The reflecting surface is at a 45° angle in order to reflect the light 90°. Light enters the entrance face of the prism. The reflecting surface then reflects the light ray 90°. The reflected light ray leaves the prism through the exit face.
EXIT FACE
FIG. A20 The 90°-or You can always determine the angle of a reflected light ray by applying the law of reflection. The law states that the angle of reflection-angle b in Fig. A21-always equals the angle of incidence-angle a in Fig. A2l. To detennine the angles, draw a line that's perpendicular to the reflecting surface-the line is called the normal, Fig. A2l. The angle of incidence is on one side of the normal; the angle of reflection is on the other side.
right-anglEr-prism.
ENTRANCE FACE
REFLECTING
SURFACE
~
-+- -
A min'or uses a silver coating on one side to reflect the light. All the light reflects from the silver coating-the glass serves only as a flat surface for the coating. But most prisms don't need silver coatings to reflect the light. The reflection takes place inside the prism; there's no glass-air surface. Thanks to an optical plinciple called total internal reflection, all of the light striking the reflecting surfaces is reflected. None of the light passes through the reflecting surface.
NORMAL
Most binoculars use porro prisms, Fig. A22, to displace the light path. In effect, a porro prism acts like two 90° plisms placed face to face, Fig. A23.
FIG. A21 Light path through the 90° prism.
REFLECTING
EXIT FACE
.
SURFACES
90' PRISMS
FIG. A22
\
The porro prism.
121BINOCULAR BASICS
FIG. A23 If you cement two 90° prisms together as shown, you have the porro prism.
Light enters one face of the porro prism and is internally reflected 90° ,Fig. A24-from one 45° surface to the other 45° surface. In Fig. A24, the dashed line is the normal. Angle a, the angle ofincidence, equals angle b, the angle of reflection. The second right -angle prism reflects the light 90° to the exit face of the porro prism.
ENTRANCE
FACE~
Notice in Fig. A24 that the light leaves the porro prism 180° opposite to the entrance direction. The light path has been displaced by a distance that corresponds to the distance between the 45° surfaces. A second porro prism returns the light ray to its original path, Fig. A25. With two porro prisms working together, the direction of the light ray remains unchanged-but the light ray is displaced. Fig. A26 shows how the two prisms are actually positioned inside the binoculars. Besides displacing the light, the two porro prisms serve another function-they provide a prism-erecting system. The two porro prisms sit at a 90° angle to one another, Fig. A27. The inverted and reverted image formed by the objective lens is then turned right side up and corrected from left to right by the porro prisms. One porro prism corrects the image in one plane; the second porro prism corrects the image in the second plane. In Section C (Adjusting Binoculars), you'll see what happens to the image if the angle between the porro prisms is greater or less than 90° .
FIG. A24 Light path through the porro prism.
ENTRANCE
RAY
I ~ I
I
V EXIT RAY
FIG. A25 Two porro prisms work together to displace the light ray without changing the direction.
FIG. A26 Positions of the porro prisms inside the binoculars.
FIG. A27 The angle between the porro prisms should be 90° . BINOCULAR BASICS/13
OBJECTIVES I
I
V
VI
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I I I I I I I I
ENTRANCE
RAY
I I I I I I I
I I I I I I I I I I
I I III I
FOCAL PLANE
<±><±> I
I
V
I
OCULARS
I
V
FIG. A28 The light displacement shortens the distance between the objectives and the focal plane-the binoculars then allow a long focal length in a compact unit.
Each side of the binoculars has two porro prisms to displace the light paths, Fig. A28. The horizontal line in Fig. A28 indicates the approximate focal pointsthe focal points of the objective lenses. As you focus the binoculars, you're moving the oculars closer to or further from that horizontal line.
FACE OF SECOND
PORRO PRISM
A prism shelf on each side of the binoculars holds a pair of porro prisms. The porro prisms sit in the bodies of the binoculars. Fig. A29. One porro prism sits on one side of the prism shelf; the other porro prism sits on the opposite side of the prism shelf, Fig. A30.
FIG. A29 Positions of the porro prisms inside the binoculars. 14/BINOCU LAR BASICS
FIG. A30 The two porro prisms in each side of the binoculars sit on the prism shelf-one porro prism on each side of the prism shelf.
VARIATIONS IN THE BASIC DESIGN Some special-purpose binoculars, such as military binoculars, place a reticle at the focal point in one side. The reticle is a thin piece of glass with etched graduations as shown in Fig. A31. As you're sighting through the binoculars, you also see the reticle. You can then use the reticle for measuring such values as distances or angles. The reticle is graduated and marked according to the purpose of the binoculars. The reticle normally fits in one end of a tube, Fig. A32. The tube mounts inside one binocular body, placing the reticle at the focal point. The binoculars shown in Fig. A30 don't use a reticle. But if they did, the reticle tube would screw into the prism shelf-above the face of the second porro prism, Fig. A30. If you're repairing binoculars professionally, the reticle presents a major cleaning problem. The reticle is magnified by the ocular. A tiny speck of dust on the reticle then appears magnified-and objectionable-when you're looking through the binoculars. We1l cover cleaning techniques in the next section. Zoom binoculars present another repair problem-the two oculars must be timed to one another. The oculars in zoom binoculars work like zoom lenses for cameras-as you zoom, the magnification of the oculars changes. If the oculars are not timed to one another, the two images will be different sizes.Since zoom binoculars area little more involved, we've given them their own section at the end of this book-Section D. The sections on disassembly and adjustments refer to binoculars that do not have zoom oculars. Please read through and understand these sections before tackling zoom binoculars. Fig. A33 shows another variation-opera glasses. Opera glasses allow two-eye viewing with a compact unit. Although very similar to standard binoculars, opera glasses have one major difference-the interpupillary distance is greater than the interobjective distance, Fig. A34. The porro prisms displace the light to shorten the required length of the opera glasses. But they don't increase the 3-dimensional effect.
Fig. A31 You see the reticle with your left eye as you're looking through the binoculars.
RETICLE
\
\\
TUBE
Fig. A32 The reticle is a thin piece of glass etched with the graduations. A tube holds the reticle at the objectivelens focal point inside the binocular body.
OBJECTIVES
lYpically the focus knob moves the objective lenses rather than the oculars. But one of the oculars is still adjustable to conect for individual eyesight. OCULARS 2
FOCUS KNOB
FIG. A33 Typical opera glasses. BINOCULAR BASICS/15
Notice in Fig. A34 that the porro prisms are displacing the light in the opposite direction to standard binoculars. For the sake of compactness, opera glasses sacrifice some of the 3-dimensional binocular characteristics. But as far as repairs and adjustments are concerned, there's little difference between opera glasses and binoculars.
INTEROBJECTIVE DISTANCE OBJECTIVE lENSES
~ PORRO PRISMS
PORRO PRISMS T
i I
However, there are some special-purpose binoculars you should not attempt to repair-binoculars that require special tools and equipment beyond the budget of most shops. For example, infrared binoculars include sophisticated circuits that convert infrared light to visible light. Our eyes aren't sensitive to infrared light; the wavelength is too long to stimulate the human eye. So, if a subject is illuminated only with infrared, we can't see that subject-unless we look at the subject through infrared binoculars. In infrared binoculars, the objective lenses focus the virtual image on a solid-state image pick-up-a device that converts the image to an electronic signal. The electronic signal is then processed by circuitry inside the binoculars and converted to a visible image-an image that's magnified by the oculars. Subject seen through the infrared binoculars appear green in color.
i
-'-'.
*&fl ' ......
i
1- INTERPUPillARY
ADJUSTABLE OCULAR
~
DISTANCE
j
I
- :
V
FIXED OCULAR
FIG. A34 The light path in opera glasses.
ENTRANCE
+
FACE",
OTHER TYPES OF PRISMS You've seen the function of the porro prisms. A pair of porro prisms increases the interobjective distance over the interpupillary distance and shortens the binocular length. The prisms also erect the image. A single prism can also be used as an erecting system. Fig. A35 shows a typical erecting prism-a right-angle prism with the top (the hatched area) cut off. Notice that the top light ray becomes the bottom light ray after passing through the erecting prism. Similarly, the bottom light ray becomes the top light ray.
FIG. A35 An erecting prism that erects the image in one plane.
The prism shown in Fig. A35 erects in only one plane. It can turn an upside down image right side up. Or it can correct a reverted image from left to right. But a prism using the roof-edge principle can erect the image in both planes. It can turn an inverted and reverted image into an image that's right side up and correctly oriented from left to right. Fig. A36 shows the roof-edge arrangement. The roof edge is formed between the two reflecting surfaces. If the roof edge is 45° to the incident light, the reflected image is both inverted and reverted. Roof-angle (or roof-edge) prisms vary according .to the numberthere's of reflecting surfaces. But the so~ewhere the prism a roof edge that erects Image. AIII roof-
16/BINOCULAR BASICS
ROOF EDGE
FIG. A36 A roof edge erects the image in two planes.
angle pentaprism, for example, has five (penta) sides; the roof-edge surfaces form two of the five sides.
OBJECTIVES
Some binoculars use roof-angle prisms for compactness. You can usually identify roof-prism binoculars by the body shape, Fig. A37. If you disassemble the binoculars, you probably won't see the individual prisms-the roof-angle prisms are normally self-contained in barrel assemblies that fit inside the binocular tubes. The theory behind the repair of roof-prism binoculars is the same as for the more conventional porro-prism binoculars. But there are many design differences. Roofprism binoculars are generally high-end, compact units. You probably should not attempt repairs on roof-angle binoculars until you're experienced in the repair of porro-prism binoculars.
QUALITY DIFFERENCES IN BINOCULARS As you cover Section B, you'll see that there are very few design variations in conventional porro-prism binoculars. But there are quality differences. The quality differences account for the wide range of prices you'll find-even though the binoculars may seem to be identical in design. The top-quality binoculars lose very little light by unwanted reflection. Whenever light enters a lens, part of that light is reflected from the front surface of the lens (a secondary reflection), Fig. A38. The transmitted light then passes through the lens and re-enters the air. But part of the light striking the rear lens surface is also reflected-it's reflected into the lens. Light that's reflected rather than transmitted is lost-it plays no part in the image formation.
FOCUS KNOB o~o~;;?;;?;?;;?;;?;;?o
OCULARS·
FIG. A37 Binoculars using roof-angle prisms generally have a sleek, compact design.
Reducing the light loss by reflection results in a sharper, brighter image. It's difficult to judge the quality difference unless you have two binoculars-a high-quality set and a low-quality set-to compare side by side. To minimize light loss by reflection, the manufacturer coats the lenses. The process involves evaporating metallic salts-such as magnesium fluoride-onto the lens surfaces. The coating reduces the effects of secondary reflection, allowing more of the light to be transmitted. You can usually recognize a coated lens by the slight color cast. The quality of the optics also has a major bearing on the price. Even the prisms vary in quality. The topquality binoculars use high-index prisms that again lose very little light by unwanted reflections or unwanted transmissions.
FIG. A38 Light path through a lens. The dashed lines show the secondary reflections. BINOCULAR BASICS/17
SECTION B-DISASSEMBLY REPAIR TECHNIQUES
&
Disassembly procedures remain fairl consistent, despite the variety in binoculars. But ythere's one type of binocular that you don't want to disassemble. Some high-end binoculars are purged and then filled with nitrogen gas. The nitrogen gas makes the binoculars waterproof and fogproof. Purged binoculars should be returned to the factory for repair-only the factory has the equipment needed to purge and refill the binoculars. Look for the words "Purged with ..." or similar on one of the cover plates. In most situations, you'll be disassembling the binoculars to reach the adjustments. Or you may have to disassemble the binoculars to clean the internal optics. If the binoculars have been dropped, optics may be broken. Plus the housing and other parts may be dented. However, when parts are required, it may be preferable to send the binoculars to the factory to repair. The factories supply parts, but not parts lists. Consequently, you can only order parts by description-and that makes it a problem to get the right part for the right model.
REAR PRISM COVERS
FIG. B1
slots in the housing or clip under a ledge. You can find the addresses and phone numbers for binocular manufacturers in another Alii publication-the Parts and Information Directory. But again, getting the right part can be a problem. In this section, we'll cover disassembly procedures and precautions. Complete disassembly of binoculars does disturb the adjustments. You should therefore disassemble the binoculars no further than necessary to make the repair.
A standard set of screwdrivers may be all you need. Most standard sets include both Phillips tips and slotted tips. A Phillips tip is slightly different than a crosspoint tip-the Phillips tip is longer with a more gradual taper. But the small Phillips tip in a standard set is usually adequate for both types. Jewelers' screwdrivers, Fig. B4, are at times needed to loosen setscrews. Setscrews are small, headless screws
TOOLS FOR DISASSEMBLY ~
You won't need many tools for binocular repair. But you do need a set of screwdrivers-both for slotted screws and for crosspoint (or Phillips) screws. The prism covers, Fig. B 1, are usually held by screws-and those screws may be either slotted or crosspoint, Fig. B2. Also, the prism clamps that hold the porro prisms in po- FIG. 82 A slotted sition may be held by screws. In other cases, the ends of the screw (left) and a prism clamps simply slip into crosspoint screw.
18/DISASSEMBLY
&REPAIR
CROSSPOINT
<
~
REGULAR
REGULAR
BLADE
BLADE {TOP VIEW}
BLADE {SIDE VIEW}
Fig. 83 A crosspoint screwdriver blade {top} compared with a regular screwdriver blade {center and bottom}.
rings-you needparts. to loosen the setscrews before you can remove the that are frequently used to lock parts such as threaded The jewelers' screwdriver has a swivel end, allowing you to turn the screwdriver without changing your grip. A set of jewelers' screwdrivers includes very small tips-tips small enough for watch repair. You may never need the smallest sizes. But you can get individual sizes. The 1.0mm and 2mm blades should handle all the setscrews you'll encounter in binoculars.
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e ~ ~
FIG. 84 A jewelers' screwdriver may be needed for headless setscrews (shown at right).
Most binocular threads are right-hand (norma/ threads rather than reverse threads). Turn most threaded parts counterclockwise to loosen, clockwise to tighten.
U LOOSEN
fJ TIGHTEN
You also need a spanner wrench, Fig. B5. Binoculars use threaded retaining rings that usually have notches for a spanner wrench. The tips of the spanner wrench fit the notches. You can then turn the spanner wrench to unscrew the retaining ring. For retaining rings, you normally want the flat tips in the spanner wrench, Fig. B5. But other parts have holes rather than notches-the holes require pointed tips in the spanner wrench. A spanner wrench like the one shown in Fig. B5 is available with both types of tips.
FIG. 85 A spanner wrench. This one has flat tips, but the manufacturer also supplies the wrench with pointed tips.
Most of the other parts in binoculars simply thread together-and you can usually unscrew the parts with finger pressure. In some cases, unscrewing the parts may take more pressure than you can provide with your fingers. For example, some binoculars are sealed for moisture resistance. The threaded parts may then be locked together with a locking agent. A flexiclamp wrench, Fig. B6, can then be helpful. The flexiclamp wrench is made of fiber, plastic, or a soft metal such as aluminum. You can then clamp the flexiclamp wrench onto the round part you want to unscrew-the soft material of the flexiclamp doesn't scratch or mar the surface of the part. The handle of the flexiclamp wrench gives you additional leverage to unscrew the part. Flexiclamp wrenches come in assorted sizes. A complete set offlexiclamp wrenches is expensive. But you won't need all the sizes provided in a set. You can purchase the flexiclamp wrenches individually as you need them. In most cases, the flexiclamp wrenches are sized in inches or millimeters-for example, a 1" flexiclamp
FIG. 86 Flexiclamp wrenches are made from materials that won't scratch the metal binocular surfaces. wrench. The size refers to the internal diameter of the opening, Fig. B6. Just measure the diameter of the part you need to unscrew. And order the flexic1amp wrench that has the closest diameter-just so that diameter is larger than the patt you want to unscrew. It's important that the flexiclamp wrench is very close in size to the part you're removing. If the flexiclamp wrench is too large, you have to squeeze the legs too far in clamping the part-that may break the wrench.
DISASSEM8L Y & REPAIRl19
Similarly, if the tlexiclamp wrench is too small, you have to spread the legs to fit the opening over the part. Again, you may break the wrench. A strap wrench, available from hardware stores, does the same job--but one wrench is all you need. Another tool that's useful for unscrewing tight parts is the softjaw plier, Fig. B7. The soft-jaw plier has soft pads attached to the insides of the jaws. You can then grip the part you're unscrewing without scratching that part. You may also want a sliding vernier caliper, Fig. B8. Quite often you'll want to maintain the original adjustment on the binoculars. By making a precise measurement before disassembly, you'll have a reassembly reference. You can then reset the adjustment to the original position.
FIG. B7 Soft-jaw pliers have cushioning pads inside the jaws.
CLEANING BINOCULAR OPTICS You may be disassembling the binoculars just to clean the optics. Moisture damage often leaves a fog or a film on the internal optical surfaces. If the binoculars have had a long exposure to humidity, there may be fungus damage to the optics. Fungus damage looks like spider webs on the optical surface. In time, the fungus will damage the coating on the optics. Cleaning the external optics may require a lens-cleaning solution. The external optics tend to get very dirty and covered with fingerprints. You can purchase commerciallens-cleaning solutions from photo dealers. Or you can use standard rubbing (isopropyl) alcohol. Many technicians prefer commercial glass cleaners such as Windex™.
FIG. B8 The sliding vernier caliper allows precise measurements.
You can also obtain lens tissues as a photo dealer. Some technicians prefer to use KimwipesTM.Others prefer the special lens-cleaning cloths such as Photo-Clear™. The lens-cleaning cloth has such a tight weave that it will pick up dirt and fingerprints-with or without a lenscleaning solution.
FIG. B9 Lens-
FIG. B10The hand
If you're using a lens-cleaning solution or Windex TM, blower. moisten the KimwipeTMor the lens-cleaning cloth. Your cleaning motion. fingers should not touch the moistened area-if they do, finger oils will be transferred to the optical surface. ing any residue left by the cleaning solution. Now start at the center of the lens. And work toward the outer edge of the lens using a spiral motion, Fig. With internal optics, you may not need the lens-cleanB9. Working from the center to the outside moves the ing solution. No fingerprints can get to the internal dirt to the edge of the lens where it can be removed. optics-but dust may be able to reach the surfaces. Use a hand blower, Fig. B 10, to blow off dust particles. If Next fog the lens with your breath. Using a dry tissue you do have to use a lens-cleaning solution, you can or cloth, again work from the center of the lens to the follow the same procedures as you do with the external outer edge. As you remove the fog, you're also remov- optics.
20/DISASSEMBL Y & REPAIR
If the binocular side has a reticle, try to restrict your cleaning to blowing off dust particles. Any dust, scratch, or residue on the reticle is greatly magnified by the ocular. And try to avoid removing the reticle from the cylinder that mounts the reticle. If you remove the reticle, you disturb the rotational position. It's then necessary to readjust the reticle. Flat optical surfaces-such as the porro prisms-require a slight! y different cleaning procedure. Rather than a spiral motion, use horizontal strokes, Fig. B II-both to apply lens-cleaning solution and to remove the residue. But there's a bigger problem in cleaning porro prismsthat's in reaching the surfaces. If you remove the porro prisms, you can fairly easily clean the surfaces. However, removing the porro prisms disturbs critical adjustments-both the collimation and the rotational adjustment for image tilt. These adjustments are described in Section C-Adjusting Binoculars. If possible, restrict your cleaning to the surfaces you can reach. Openings in the prism shelf allow you to reach the entrance and exit surfaces of each prism pair. You can then clean these surfaces without removing the porro prisms. But cleaning the surfaces that transfer light from one porro prism to the other do require removing the porro prisms-and disturbing the adjustments.
ning of this publication-Vivitar for the tools you'll need).
is one of the sources
The grease on the threads of the adjustable ocular may be a very light grease. If you find that the adjustable ocular turns too freely because of wear in the threads, you may be able to correct the problem by using a heavier grease. But some binoculars use plastic-rather than metalocular housings. If the threads are plastic, be sure to use a plastic-compatible grease such as a losoid grease. A grease that isn't compatible with plastic may in time damage the threads. To lubricate the threads of the adjustable ocular, apply the grease around 1/3-1/2 of the way up the threads, Fig. B12--either to the threads of the ocular or to the threads in the ocular arm. Then screw in the ocular. Screwing the ocular in and out applies the grease to the remaining threads. Excess grease will be pushed out at the ends of the threads. Use a KimwipeTM to wipe off the grease.
CLEANING METAL PARTS The metal parts that most frequently need cleaning are the threads of the adjustable ocular-and the threads in the ocular arm that receive the adjustable ocular. It's often necessary to clean the old grease from the threads. Then relubricate the threads. Isopropyl (rubbing) alcohol works well as a cleaning solution-it's safe both for metal and for plastic. To scrub the threads, you can use an old toothbrush. After you scrub the threads, use tissues such as to pick up the alcohol. Dried, caked-on Kimwipes grease can be difficult to remove. You may have to scrub and dry the threads several times.
FIG. B11 Cleaning motion for the bottom of the porro prism.
™
LUBRICATION Two places in the binoculars always have grease lubrication-the hinge and the threads of the adjustable ocular. The hinge grease is a heavy, sticky grease. Binocular manufacturers use a special binocular grease. In some cases, the manufacturers will supply binocular grease to repair shops. Or you can use the focus-mount greases available from Vivitar (address at the begin-
GREASE THESE THREADS
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L
FIG. B12 Apply grease around 1/3 to 1/2 the way from the ends of the threads. DISASSEMBLY & REPAIRl21
You can check the feel as you turn the adjustable ocular. If the adjustable ocular feels too tight, you may have to remove some of the grease-or apply a lighter grease. If the adjustable ocular turns too freely, you may have to add grease-or apply a heavier grease.
DECORATOR
CAP
If the binoculars have a focus knob, the parts that move the oculars also use grease. The focus knob threads into the hinge pin. And the ocular shaft that carries the ocular arms threads into the focus knob. Use grease on the threads of both parts. If the binoculars use a rocker arm, lubricate the cam slot of the rocker arm with grease. You'll see all these lubrication points during the disassembly that follows. But in general, use the heavy binocular grease on any sliding surfaces-surfaces that bear against one another when you change the distance between the binocular sides. Also lubricate the threads of threaded parts that turn during some operation-for example, the threads of the adjustable ocular and the threads of the focus knob. REAR PRISM COVERS
DISASSEMBLY TECHNIQUES Frequently you want to disassemble the binoculars just far enough to reach the adjustments-disassembl y steps to reach the adjustments are described in the section Adjusting Binoculars. You may want to skip now to Adjusting Binoculars and go through just the disassembly you need. Or, if you have a pair of junk binoculars, you may want to go through a complete disassembly-just for familiarity. If the binoculars are repairable, they'll also give you practice in setting the adjustments. But if you're working on repairable binoculars, there are some rules to follow that will make adjustment easier. Here's one of the most important rules-disassemble only one side of the binoculars at a time. Reassemble that side before you disassemble the other side. Why? Whenever you disassemble one side, there's a risk of disturbing adjustments. But you still have the other side-the side you haven't disassembled-to use as your standard. Once you've adjusted the reassembled side, you can disassemble the other side. You can now use the side you've already adjusted as your standard. 1\vo of the adjustments you can disturb are collimation and rotational error. If the binoculars are out of collimation, the images formed by the two sides won't coincide. As a result, you may see two images. Rotational error refers to image tilt. One or both of the im-
221DISASSEMBL Y & REPAIR
FIG. B13 Binoculars after unscrewing objective-lens tube. ages may appear to be tilted. The section Adjusting Binoculars describes these two adjustments in detail. But as we go through disassembly, we'll note which steps may disturb adjustments-and what you can often do to save the adjustments. If you take apart the oculars, there's another adjustment you can disturb-the ocular focus. We'll describe the procedures for adjusting the oculars in this section. Objective-lens parts: Many major parts of the binoculars simply screw into place. In most binoculars, the decorator caps, Fig. B 13, unscrew. Also, the complete objective-lens tube screws into the binocular body. lhreaded rings and tubes can present a slight problem on reassembly. The threads of the decorator cap and of the objective-lens tube are fine (as opposed to coarse). If you miss the proper starting thread, you can crossthread the parts. A cross-threaded objective-lens tube, for example, will sit at a slight angle to the binocular body. One technique you can use to find the proper starting thread is to first turn the part in the opposite direction. To screw in the objective-lens tube, you turn the objective-lens tube in a clockwise direction (as seen from the front). But if you have trouble finding the starting thread, first turn the objective-lens tube in a counter-
clockwise direction-the direction you used for removing the objective-lens tube.
ECCENTRIC
RING
When you reach the starting thread, you'll hear or feel a slight" click." Then, when you hear the "click," turn the objective-lens tube in a clockwise direction. To remove the objective lens, unscrew the objective cap. A retaining ring, Fig. B 14, holds the objective lens in place. But be careful-removing the objective lens may disturb the adjustment for collimation. Do not remove the retaining ring unless you want to collimate the binoculars. If you're disassembling for practice-or if it's really necessary to remove the objective lens-use your spanner wrench to unscrew the retaining ring. You can now lift out the objective-lens cell with the objective lens. There may be a loose eccentric ring around the front shoulder of the objective-lens cell, Fig. B 14. If so, you've just lost the collimation adjustment-the eccentric shifts the position of the objective lens to align its optical axis (optical center).
RETAINING
FIG. 814 You can see the eccentric ring under the retaining ring. When you see an eccentric ring, you know that you can't remove the objective lens without disturbing the collimation.
You don't have to take out the objective lens to remove the objective-lens tube, Fig. B 13. In most binoculars, the objective-lens tube screws into the binocular body. But beware-removing and replacing the objectivelens tube may also disturb collimation. Why? Remember that the eccentric ring around the objective lens shifts the lateral position of the objective lens. Rotating the objective-lens tube also shifts the objective lens. If you unscrew the objective-lens tube, then, you want to return the objective-lens tube to the original position. You can change that original position by screwing in the objective-lens tube more tightly-or by not screwing in the objective-lens tube to the original tightness. How much torque you apply when screwing in the objective-lens tube then affects the collimation. You can normally maintain the original position by marking the objective-lens tube. Before you unscrew the objective-lens tube, place a pair of reference marks, Fig. B 15-one on the objective-lens tube and one on the binocular body or cover plate. If you can reach a place on the binoculars that can't normally be seen, you can use scribe lines-scratches in the metal placed by a sharp tool. You may be able to make your scribe lines sufficiently small that they can't be easily detected. Or you can use a soft pencil to make your reference marks. You can wipe off the pencil marks after you complete the reassembly. Now hold the binoculars by the body. Unscrew the
RING
OBJECTIVELENS TUBE
REFERENCE MARKS
_/
IT
FIG. B15 Before disassembly, mark the rotational position of the objective-lens tube. Your reference marks tell you how much torque to apply when you screw in the objective-lens tube. DISASSEMBL V & REPAIRl23
complete objective-lens tube, Fig. B 13. On reassembly, screw in the objective-lens tube until it comes against the binocular body. Then check the alignment of your reference marks. If the reference mark on the objective-lens tube hasn't reached the fixed reference mark, add some torqueturn in the objective-lens tube more tightly. Whatifthe reference mark on the objective-lens tube has moved slightly past the fixed reference mark? Back out the objective-lens tube until your reference marks align. In many binoculars, the objective-lens tubes are not separate parts-the body and the objective-lens tube may be one assembly, Fig. B 16. In that case, there's no prism cover on the objective-lens side. You reach the porro prisms by removing the prism cover on the ocular side-a procedure we'll describe in a moment.
Removing the prism covers: In Section A, you saw that the porro prisms usually seat in prism shelves that are built into the binocular bodies. To reach the front porro prism, it's necessary to remove the front prism cover, Fig. B 13. Reach the rear porro prism by removing the rear prism cover, Fig. B 13. You can reach the front prism cover by unscrewing the objective-lens tube as previously described. If there isn't a front prism cover, the objective-lens tube and the body
OCULAR TUBES
FIG. B16 The objective-lens tube and the body on each side of these binoculars is one piece. It's then necessary to remove the oculars and the rear prism covers to reach the porro prisms. are one piece, Fig. B16. The prism shelves are then separate parts. You can remove the complete prism shelf together with both porro prisms-first take off the rear prism cover, Fig. B16. If both oculars are adjustable, as in Fig. B 16, the ocular tubes normally screw into the binocular bodies. Just unscrew the ocular tubes, Fig. B 17. You can then remove the rear prism covers after taking out their retaining screws, Fig. B 18.
COVER-PLATE SCREWS
----------REAR PRISM COVER
OCULAR TUBE
FIG. B17 Here the complete ocular assembly unscrews. The ocular tube screws into the binocular body. 24/DISASSEMBL Y & REPAIR
FIG. B18 Back view, rear prism cover plate after unscrewing left-side ocular.
However, if the binoculars have a focus knob or rocker arm, you can usually remove the complete ocular assembly-both oculars as a unit. The procedure depends on the design. And, in some cases, you have a choice of procedures.
Removing the ocular assembly from a rocker-arm design: If the binoculars use a rocker arm, Fig. B 19, there are a couple of disassembly methods you can use. You can normally remove the ocular assembly together with the hinge pin-that's probably the easier method. First remove the decorator plate, Fig. B 19. The decorator plate normally snaps into place. Spring up one end of the decorator plate to disengage the snaps. You can now reach the screw on the hinge pin, Fig. B20. The hinge-pin screw passes through the carn slot of the rocker arm. Remove the hinge-pin screw, Fig. B20. Then lift out the ocular assembly and the hinge pin toward the ocular end of the binoculars. Typically, the binocular sides won't separate. Separating the binocular sides requires removing the threaded rings at the ends of the hingepin bearings.
FIG. 819
HINGE-PIN
SCREW
On reassembly, slide the hinge pin into place with the ocular assembly. Move the rocker arm until you can see the hinge-pin screw hole through the rocker-arm slot. Then replace the hinge-pin screw, Fig. B20. Alternately, you can remove the ocular arms from the hinge pin. Take of the IPD (interpupillary distance) scale-it's held by one screw, Fig. B21. You can then see the rear hinge-pin screw-the screw that holds the ocular arms to the rear end of the hinge pin. Remove the screw and lift out the ocular arms with the oculars as an assembly.
I I I
o
7<(8j
IPDSCALE
FIG. 820 Rocker arm with decorator plate removed.
a~ ~
~
FIG. 821 Adjusting the interpupillarydistance scale. Match the scale reading to distance D.
On reassembly, adjust the position of the IPD scale, Fig. B21. The scale reading must match the distance between the centers of the eyelenses--distance D in Fig. B21. Spread the binocular sides until distance D equals one of the calibrations on the IPD scale (60mm or 70mm in Fig. B21). Then loosen the screw holding the IPD scale. Rotate the IPD scale until the proper calibration aligns with the index. Hold the IPD scale in position as you retighten the screw.
DISASSEM8L Y & REPAIRl25
Removing the ocular assembly from a focus·knob design: If the binoculars use a focus knob, Fig. B 22, you again have a choice of disassembly techniques. Each has its own advantages and drawbacks. One method is to remove the ocular assembly together with the hinge pin. You'll then find that the binocular sides will separate. Although you can keep the binocular sides together, there's another drawback:
Removing the hinge pin often disturbs the adjustment on the hinge pressure-how much pressure is required to spread the sides further apart or to move the sides closer together. You can usually see the adjustment after unscrewing the decorator screw at the front of the hinge pin, Fig ... B22 and Fig. B23. Use the pointed tips in your spanner wrench to unscrew the decorator screw. Some binoculars use a decorator cap that has a pressure fit. Or there may be a decorator disc that's held by one screw.
FIG. B22 Binoculars With a focus knob.
Removing the decorator screw uncovers the adjusting screw, Fig. B24. The adjusting screw threads into the end of the hinge pin. A locking setscrew, Fig. B24, often holds the adjusted position of the adjusting screw. After loosening the setscrew, you can turn the adjusting screw. Turning in (tightening) the adjusting screw increases the hinge pressure-it then takes more force to change the interpupillary distance. Turning out (loosening) the adjusting screw decreases the hinge pressure. You must remove the adjusting screw to take out the hinge pin-and that loses the pressure adjustment. If you're working on your own binoculars, there's no problem-you can adjust the pressure to suit your own preferences. But if you're working on a customer's binoculars, changing the hinge pressure may result in an unhappy customer.
FIG. B23 Front view of the binoculars.
The customer will quickly notice any difference in the hinge pressure-especially if the customer uses the binoculars frequently. The customer may then think that you haven't repaired the binoculars properly-the binoculars "feel" different. Ideally, you should adjust the hinge to the same pressure as it originally had-just to keep the customer satisfied. But the customer is less likely to be unhappy if the hinge pressure is slightly tighter than before (rather than slightly looser than before). If the binocular sides move more freely, the customer may think you've failed to tighten something sufficiently. But if the adjustment feels tighter, the customer may feel that you've done a thorough repair-you've "tightened up" the sides.
26/DISASSEM8L
Y & REPAIR
FIG. 824 Front of the binoculars, decorator screw removed.
To remove the oculars with the hinge pin, loosen the locking setscrew (if used), Fig. B24. Use a large screwdriver or the flat tips in your spanner wrench to unscrew the adjusting screw. Now slide out the complete ocular assembly-together with the hinge pin-to the back of the binoculars, Fig. B25. As mentioned earlier, it's now possible to separate the binocular sides. If you do separate the binocular sides, watch for spacer washers-the washers, when used, fit between the binocular sides at the hinge positions. Like the adjusting screw, the washers are used to adjust the hinge pressure. The hinge pin and the hinge-bearing surfaces on the binocular bodies should be lubricated with the heavy binocular grease. Because of the grease, the washers will stick to just about anything. Make sure the washers are in position before you reassemble the binocular sides. With the ocular assembly removed, you can unscrew either of the ocular tubes, Fig. B25-the ocular tubes thread into the binocular bodies. It's usually necessary to remove the ocular tubes to take off the rear prism covers.
FIG. B25 Removing the ocular assembly.
You can now remove the rear prism covers. The rear prism covers may be held by screws. Or you may find that only the ocular tubes hold the rear prism covers. Some binoculars hide the screws holding the rear prism covers. If the binoculars have a rubberlike covering, you may have to peel aside the covering to reach the screws. You may find that you can then remove the rear prism covers without unscrewing the ocular tubes. Earlier we mentioned that you can also remove the ocular assembly without taking out the hinge pin. If you don't unscrew the adjusting screw, Fig. B24, you won't disturb the hinge-pressure adjustment. One method is to partially disassemble the focus knob. Before looking at this technique, you should understand the focus-knob design. Fig. B26 shows the hinge pin with the ocular assembly removed. The ocular arms fit over the shoulder on the ocular shaft.
HINGE PIN
FOCUS KNOB
OCULAR SHAFT SHOULDER FOR OCULAR ARMS
Both the focus knob and the ocular shaft are threaded. The focus knob screws into the end of the hinge pin. And the ocular shaft screws into the focus knob. If the ocular arms are removed, the ocular shaft turns with the focus knob. The focus-knob assembly screws in or out along the hinge-pin threads. The ocular shaft simply turns with the focus knob.
FIG. 826 Hinge pin and focus-knob assembly.
DISASSEMBLY & REPAIRl27
But, with the binoculars assembled, the ocular arm can't rotate. The ocular arms prevent the ocular shaft from turning with the focus knob. Since the ocular shaft can't rotate, it's forced to move in or out along the threads. The ocular shaft then carries the ocular arms in or out. The oculars move closer to the binocular bodies or further from the binocular bodies.
HINGE PIN
In Fig. B27, we've unscrewed the focus-knob assembly from the hinge pin. Here you can see the threads on the focus-knob assembly and on the ocular shaft. You can separate the ocular shaft from the focus-knob assembly after removing the stop screw, Fig. B27the stop screw prevents the ocular shaft from unscrewing from the focus knob. Then unscrew the ocular shaft, Fig. B28. The ocular shaft has a left-hand (or reverse) thread. If you're looking at the front of the focus knob, turn the ocular shaft in a clockwise direction. The ocular shaft then unscrews from the focus knob. Thm the ocular shaft in a counterclockwise direction to screw it into the focus knob. By unscrewing the ocular shaft, you can leave the hinge pin and focus knob in the binoculars. Only the ocular shaft comes out with the ocular assembly. But there's one timing point you can lose-the position of the focus knob. Since the focus knob is threaded, it moves in and out as you focus the binoculars. Starting the focus knob at the wrong position may limit the movement of the ocular assembly. Let's say, for example, that the focus knob has been started too far in-too close to the binocular bodies. Then, as you turn the focus knob to move in the oculars, the focus knob bottoms-it comes against the top of the hinge pin before the oculars have moved in fully. And, when you move the oculars fully out, Fig. B29, the oculars still aren't as far away from the binoculars as they should be. The focus knob hasn't turned out far enough. You then want to start the focus knob at its original position. One way is measure the distance between the underside of the focus knob and the topofthe hinge pin when the threads of the ocular shaft disengage. Here's the procedure:
STOP SCREW AT END OF OCULAR SHAFT
FOCUSKNOB ASSEMBLY
----OCULAR SHAFT
FIG. 827 Hinge pin separated from focus knob.
V--
STOP SCREW
FOCUS KNOB
OCULAR SHAFT
Remove the decorator screw or cap at the objective end of the hinge pin. You can now reach the stop screw at the end of the ocular shaft, Fig. B27, through the hole in the adjusting screw, Fig. B30. Inselt a long, thin screwdriver through the adjustingscrew hole, Fig. B30. Then unscrew the stop screw. You probably won't be able to completely remove the
28/DISASSEM8L Y & REPAIR
FIG. 828 Ocular shaft separated from focus knob.
stop screw-the ably too small.
hole in the adjusting screw is prob-
FOCUS KNOB
Now turn the focus knob to move the ocular arms away from the binocular bodies-turn the focus knob counterclockwise as seen from the ocular end. The ocular shaft unscrews from the focus knob. Stop turning the focus knob the moment the ocular shaft disengages, Fig. B31. You can then measure the distance between the underside of the focus knob and the top of the hinge, Fig. B3l. The distance marks the point at which the ocularshaft threads disengage from the focus-knob threads. As you're working on the binoculars, the focus knob may turn. But you can return the focus knob to the starting position by setting the same space gap. On reassembly, set the focus knob to the measured distance. Then slide the ocular assembly into place. You may have to shift the oculars slightly until each ocular fits over its ocular tube.
FIG. 829 HOLE IN ADJUSTING
SCREW
Next turn the focus knob clockwise as seen from the ocular end. The focus knob draws in the ocular shaft. Continue turning the focus knob until the oculars move in as far as they will go. Then work through the adjusting-screw hole to tighten the ocular-shaft stop screw. Finally, there's one more technique you can use-you can remove the ocular arms from the ocular end of the hinge pin (from the ocular shaft). Thrn the focus knob to move the oculars as close as they will go to the binocular bodies; the ocular shaft then extends a minimum distance from the focus knob.
FIG. 830 OCULAR SHAFT
MEASURE
DISTANCE
Again you'll probably have to disturb the adjustment on the IPD scale. After removing the IPD scale or decorator ring, the ocular arms may lift off the ocular shaft. Or you may have to remove a screw holding the ocular arms. Avoid turning the ocular shaft or the focus knob with the ocular assembly removed. If the ocular shaft is at a different position with respect to the focus knob-or if the focus knob has turned-you may not get the full focus movement. Which of the three procedures you use depends partially on individual preferences-and partially on the particular binoculars. Removing the hinge pin together with the ocular assembly sounds easier. But the procedure disturbs the hinge-pressure adjustment. Also, the adjusting screw, Fig. B30, can be difficult to removenot only is the adjusting screw very tight, its threads may be sealed with a locking agent.
OCULAR
ARMS
FIG. 831 DISASSEMBLY & REPAIRl29
FACE OF OBJECTIVE-SIDE PORRO PRISM
FIG. B32 Binocular side with the rear prism cover removed.With the hinge pin removed, you can separate the binoculars into two halves. Here you can see the porro prism on the ocular side of a binocular half. In this design, one end of the prism clamp is held by a screw. The other end slides under a lip in the binocular body. Removing the ocular arms from the rear end of the hinge pin may also lose adjustments-the position of the focus knob and the position of the ocular shaft with respect to the focus knob. If either part is out of position, you won't have the full range of movement in the ocular assembly. Unscrewing the ocular shaft from the focus knob may then be the safest and easiest techniqueas long as you note the focus-knob position.
Porro prisms, prism shelves: Once you've removed the prism covers, you can reach the porro prisms. Removing individual porro prisms or a complete prism shelf can disturb adjustments. Remember the disassembly precaution-disassemble only one side of the binoculars at a time. You then have a standard for adjustments on the side you've disassembled. As we go through the disassembly, we'll point out methods you can often use to retain the adjustments. After you remove the front prism cover, you can reach
30/DISASSEMBL Y & REPAIR
the porro prism on the objective side. Remove the rear prism cover to reach the porro prism on the ocular side. A clamp-and usually dabs of cement or wax-hold each porro prism in the adjusted position, Fig. B32. Leave the pon'o prism in place if you don't want to disturb the adjustment-the adjustment affects both collimation and image tilt. Note that you can reach one face of the porro prism on the other side of the prism shelf, Fig. B32. You can then clean the exposed prism face without further disassembly. And, after removing the front prism cover, you can reach one face of the other porro prism. However, to clean the unexposed faces, you'll have to remove the porro prisms. First note the position of the porro prism. Each porro prism fits into a recess in the prism shelf, Fig. B32. The recess is slightly larger than the porro prism. If the porro prisms weren't intended for adjustment, they
may fit snugly in the recesses. But if the binoculars were designed for porro-prism collimation, the recesses may be quite a bit larger than the porro prisms.
CEMENT
PRISM CLAMP
You can then slide the porro prism in one direction or the other. However, you'll probably find that the porro prism is against one end of the recess. For example, in Fig. B33 (top) the porro prism is against the left-hand end of the recess. Make a note or sketch to indicate the adjusted position. Then, on reassembly, move the porro prism against the same end of the recess. The dabs of cement used to hold the porro prism in the adjusted position, Fig. B33, can also provide reassembly help. You can cut the dabs to free the porro prismleave part of the cement on the prism and part on the prism shelf. On reassembly, align the dabs of cement. Quite often you'll find that impact has broken loose the cement. The porro prisms may then have shifted, throwing off the adjustments. Again you can use the old cement as a guide as to the original prism adjustments. Match up the cement dabs to reposition the prisms. It's possible that the entire dab of cement remains on the prism shelf. But you may still be able to see the shape of the cement dab on the side of the porro prism. Just move the porro prism until the imprint of the cement matches the position of the cement dab.
EXPOSED FACE OF OCULAR-SIDE PORRO PRISM
To take out the porro prism, remove the prism clamp, Fig. B32 and Fig. B33. The prism clamp may be held by screws. Or the ends of the prism clamp may simply fit into slots in the body. The prism clamp then holds itself in place because of its spring action-the ends of the prism clamp spring upward. In some designs, the prism clamp simply clips over the edges of the prism shelf. If the prism clamp fits into body slots, free one endpush down the end of the prism clamp to overcome the spring action. Then turn the prism clamp as needed until you can free the end from the slot. You can now free the other end and lift out the prism clamp. You may now be able to lift out the pon'o prism. Or you may have to cut or pull loose the dabs of cement.
Disassembly and adjustment of the oculars: There are many variations in the disassembly of the oculars, depending on the particular binoculars. Normally you can disassemble the fixed ocular without disturbing any adjustments (although, as we'll later describe, there are exceptions). Taking apart the adjustable ocular, however, does disturb an adjustmentthe diopter adjustment. Yet it's usually the adjustable ocular you'll have to dis-
FIG. B33 The prism shelf with the porro prism in place (top) and removed (bottom).
assemble. Normally the problem is the grease on the adjustable-ocular threads. With age, the grease dries. The dried grease can cause the ocular threads to seize. You may then find that you can't even turn the adjustable ocular to set the diopter adjustment. Or you may find that the adjustable ocular turns too freely. The problem may then be wear in the threads. As mentioned earlier, you can often correct the problem by applying a heavier grease. Setscrews (typically three setscrews, but there may only be one) often hold the control knob to the adjustable
DISASSEMBLY
& REPAIRl31
ocular, Fig. B34. You may be able to see the slotted ends of the setscrews as in Fig. B34; or you may have to work through holes in the control knob to reach the setscrews, Fig. B35. As you turn the control knob, the adjustable ocular screws in or out. You can loosen the setscrews to change the position of the adjustable ocular with respect to the control knob. To remove the control knob, you may have to first remove the rubber eyecup, Fig. B34. The eyecup may lift off. Or it may unscrew. Then loosen the setscrews, Fig. B34, and lift off the control knob, Fig. B35. You can now turn the adjustable ocular in or out, changing the position-and the adjustment.
EYECUP
SETSCREW
FIG.834 Three setscrews normally hold the control knob to the adjustable ocular. After loosening the setscrews, you can adjust the position of the control knob.
On reassembly, first turn the adjustable ocular to the 0diopter position. Then seat the control knob with its 0 calibration aligned with the index. Finally, tighten the setscrews. To find the O-diopter position, ocular as a reference. The fixed o diopter (no correction). Look lar with either eye. Adjust the target appears sharp.
you can use the fixed ocular is already set to through the fixed ocufocus knob until your
Now use the same eye to look through the adjustable ocular. Thrn the adjustable ocular until the same target appears sharp; the adjustable ocular is now set to 0 diopter. Seat the control knob with its 0 calibration aligned with the index-make sure you don't turn the adjustable ocular as you're seating the control knob. TIghten the setscrews to hold the control knob to the adjustable ocular. With some binoculars, as mentioned earlier, both oculars are adjustable. Here it's even more desirable to disassemble only one ocular at a time. Let's say you've disassembled the right ocular. Use the left ocular as your standard to set the position of the right ocular.
HOLE FOR SETSCREW
CONTROL
KNOB
ADJUSTABLE
OCULAR
OCULAR ARM
FIG. 835 The control knob removed from the adjustable ocular.
First look through the left ocular with either eye. Thm the control knob until your target appears sharp. Then note the scale reading on the ocular. For example, say the target appears sharpest with the ocular set to +I diopter. Next look through the right ocular-use the same eye and the same target. Thm the right ocular until the target appears sharp. Now seat the right-ocular control knob to match the setting of the left ocular. In our example, the target appears sharpest with the left ocular set to + 1. Seat the right -ocular control knob at the +1 position and tighten the setscrews.
321DISASSEM8L Y & REPAIR
If you can't use one ocular as your standard, you may have to use another pair of binoculars to determine your own correction. For example, say you're working on binoculars in which both oculars are adjustable. And the adjustment has been lost on both oculars. Use another pair of binoculars to determine your own diopter correction for one eye. Then set each of the oculars in the binoculars you're repairing to the same correction. The scale calibrations on another pair of binoculars may not be exactly the same. But they'll be close.
The knob for the fixed ocular may simply lift off after you loosen the setscrews. If there are no setscrews, the knob for the fixed ocul ar may be threaded-in that case, unscrew the knob.
HOLE FOR SETSCREW
Once you've removed the knob, you may be able to simply lift out the fixed ocular. The fixed ocular normally slides into the sleeve on the ocular arm. In some cases, it's necessary to unscrew the fixed ocular. A setscrew may then lock the fixed ocular in position, Fig. B36. Here there's an adjustment on the fixed ocular. Screw in the fixed ocular to the O-diopter position and then tighten the setscrew. If the fixed ocular has an adjustment, use the adjustable diopter to set the position. Turn the adjustable diopter to the O-diopter setting. Then use the technique described earlier to set the fixed ocular to 0 diopter. The adjustable ocular may be more difficult to remove. Once you remove the control knob, you will normally find that you can't completely unscrew the adjustable ocular-you can only turn the adjustable ocular to its maximum extended position.
FIXED OCULAR
LOCKING SETSCREW
FIG. 836 A fixed ocular that can be adjusted for O-diopter correction.
It's then necessary to remove the complete ocular assembly using one of the techniques described earlier. With the ocular assembly removed, you can turn the adjustable ocular in a clockwise direction (as seen from the back of the binoculars)-the threads move the adjustable ocular toward the front of the ocular assembly. Keep turning in the adjustable ocular until you can unscrew it from the ocular arm. Or you may find that the threads for the adjustable ocular are on a separate ring-the adjustable ocular slides into the threaded ring. You may then be able to lift out the ocular toward the back of the binoculars. But you'll probably have to remove the ocular assembly to take out the threaded ring. Turn in the threaded ring until you can remove it from the front of the ocular assembly-just as you would remove a threaded ocular. With some designs, it's necessary to remove the adjustable ocular before you can remove the control knob. Fig. B39 shows an example. The stop on the ocular arm limits how far you can turn the control knob. The stop also prevents you from lifting off the control knob until you unscrew the adjustable ocular. First remove the ocular assembly and lift off the rubber eyecup. Loosen the setscrews around the outer circumference of the control knob. Now unscrew the adjustable ocular from the front of the ocular assembly, Fig. B37 (turn the adjustable ocular clockwise as seen from the eyelens side).
FIG. 837 DISASSEM8L Y & REPAIRl33
You can now remove the control knob--tilt the control knob slightly to clear the stop on the ocular arm, Fig. B37. With the adjustable ocular in place, you can't tilt the control knob enough to clear the stop.
OCULAR
HOUSING
On reassembly, first seat the control knob. Then screw in the adjustable ocular from the front of the ocular arm, Fig. B37. Temporarily tighten the setscrew holding the control knob to the adjustable ocular. Or, if there are three setscrews holding the control knob, tighten just one. Replace the ocular assembly. You can now adjust the adjustable ocular. Thrn the control knob to set the adjustable ocular to 0 diopter-use the fixed ocular as a reference. Then loosen the setscrew you tightened. Without turning the adjustable ocular, turn the control knob until its 0 calibration aligns with the index. TIghten the setscrews. EYELENS
VARIATIONS IN OCULARS We mentioned that you'll encounter several variations in ocular disassembly. But there are a couple of major variations in ocular design we should mention herethe particular designs are covered in the following sections. The oculars are considerably different-and more complex-in zoom binoculars. As mentioned earlier, the oculars in zoom binoculars use movable elements to change the magnification. Section D covers the zoom oculars. You'll also encounter some binoculars that provide the collimation adjustment on the oculars rather than on the objectives. The collimation adjustment then shifts the eyelens-the lens closest to the back of the ocular. After you remove the eyecup, you'll be able to see if the eyelens is adjustable. The eyelens may look like a miniature version of the objective lens in Fig. B 14. Here the eyelens cell has an eccentric shoulder. An eccentric ring fits around the shoulder of the eyelens cell. And a retaining ring screws over the retaining ring to hold the adjustment. After loosening the retaining ring, you can turn the eccentric ring to shift the eyelens.
FIG. B38 An adjustable eyelens.
oculars with the eyelens are the same as those for collimating the binoculars with the objective lens-only the actual adjustment points are different. Section CAdjusting Binoculars--covers the collimation procedures.
DISASSEMBLY OF OPERA GLASSES After working on conventional binoculars, you probably won't have any trouble figuring out the disassembly of opera glasses. But there are some basic differences. In standard binoculars, as you've seen, you remove the oculars as an assembly. In opera glasses, you normally remove the objective lenses as an assembly. Here's a typical disassembly: The opera glasses shown in Fig. B39 have a decorator cap at the center of the focus knob. The cap is cemented in position. Slide a thin tool, such as a small jewelers' screwdriver, under the edge of the cap. Pry off the cap, being careful to avoid cosmetic damage.
Another variation uses three setscrews around the outside circumference of the ocular, Fig. B38. The setscrews position the eyelens. By loosening one setscrew-and tightening another setscrew-you can shift the position of the eyelens.
You can now see a crosspoint screw in the center of the focus knob. Remove the screw. Now turn the focus knob in a clockwise direction as seen from the back of the
You should normally avoid disturbing the adjustments on an adjustable eyelens. However, if the binoculars are out of collimation, the eyelens becomes your adjustment point. The procedures for collimating the bin-
Stop turning the focus knob the moment the tlu'eads of the objective-lens shaft disengage. Then measure the distance between the back of the focus knob and the
34/DISASSEMBL Y & REPAIR
opera glasses. The shaft of the objective-lens assembly unscrews from the focus knob.
OBJECTIVE
body of the opera glasses-just as you measure the position of the focus knob with regular binoculars.
LENSES
Lift out the objective-lens assembly-the two objective lenses and the shaft-toward the front of the opera glasses, Fig. B40. Finally unscrew the focus knob from the hinge pin-this time, turn the focus knob in a counterclockwise direction as seen from the back of the opera glasses. Next unscrew the two oculars-the oculars just thread into the body. With the oculars removed, you can lift off the two prism-cover plates. Notice that it was necessary to remove the focus knob before the prism-cover plates could be removed. You can now reach the porro prisms. lYpically the prism shelves are separate parts. Each prism shelf is held by three screws. There may also be adjustment screws on the prism shelves; each prism shelf may have two or three adjustment screws for adjusting the collimation. For now, you might shelves-we'll cover tion. You can at this front porro prism for
prefer to not disturb the prism the adjustments in the next sectime reach one surface on each cleaning.
\ .
FIG. B39 TYPical opera glasses.
To reach the porro-prism surfaces on the objective-lens side, unscrew the two objective-lens tubes, Fig. B40. Each objective-lens tube has a lens-part of the objective-lens assembly. OBJECTIVE-LENS
Most of the optics are now available for cleaning. But chances are you're working on the opera glasses because of the need for adjustment. In that case, you'll want to partially reassemble the opera glasses. Follow the reassembly procedure. But temporarily leave off the prism-cover plates. You can then reach the prism-shelf adjustments. Proceed to the next section for the adjustments.
FOCUS KNOB
ADJUSTABLE OCULAR
ASSEMBLY
OBJECTIVELENS TUBES
t OBJECTIVELENS SHAFT
REASSEMBLY OFTHE OPERA GLASSES Replace the prism-cover plates (unless you're going to adjust the opera glasses) and the oculars. The ocular with the diopter adjustment goes on the left-hand sidethe side on which the prism-cover plate has an index dot. If you leave off the prism-cover plates to reach the adjustments, you can still screw the oculars into the body. Screw the focus knob onto the threads at the end of the hinge pin-keep turning the focus knob clockwise until it's at the distance you measured during disassembly. Then insert the objective-lens assembly, Fig. B41. You can only insert the objective-lens assembly part
FIG. 840 Removing the objective-lens assembly. DISASSEM8L Y & REPAIRl35
way. The objective-lens shaft, Fig. B41, is then blocked by the focus knob. ••••••••
Now turn the focus knob counterclockwise (as seen from the back) to draw in the objective-lens assembly. Help the two objective lenses pass over the objectivelens tubes as you turn the focus knob. Draw in the objective-lens assembly as far as it will go. Then replace the screw at the end of the objective-lens rod (center of focus knob). Use a touch of Pliobond to cement the decorator plate at the center of the focus knob.
'. ,;:t:.
OBJECTIVELENS TUBES
SUMMARY OF DISASSEMBLY RULES AND PRECAUTIONS 1. Disassemble only one side of the binoculars at a time. You can then use the side you haven't disassembled as your standard for setting up adjustments. Adjust the side you've just reassembled before disassembling the other side. The side you've just adjusted then becomes your standard. 2. If the objective lenses are adjustable, you can see the eccentric rings from the front (under the retaining rings that hold the objective lenses). Removing the retaining ring will then disturb the collimation adjustment. 3. If the binoculars use eccentric rings on the objective lenses, be careful when unscrewing the objective-lens tubes-a change in the rotational position of the objective-lens tube affects collimation. Mark the objectivelens tubes before disassembly. On reassembly, use just enough tightening torque to align your marks. 4. You can usually reach the front porro prisms by unscrewing the objective-lens tubes and removing the front prism-cover plates. If the objective-lens tubes are not separate parts, the prism shelves are removable-it's then necessary to remove the prism shelves to reach the front porro prisms. But be careful-there may be adjustment screws on the prism shelves. 5. To reach the rear porro prisms, it's usually necessary to take out the ocular assembly. You can often remove the ocular assembly as a unit together with the hinge pin. Removing the hinge pin allows you to separate the two binocular sides. However, there's a problem with removing the hinge pin-you then disturb the hingepressure adjustment. A customer will quickly notice any change in the amount of pressure required to spread the binocular sides. To maintain the hinge pressure, you can unscrew the ocular shaft from the focus knob and leave the hinge pin in the binoculars. 6. Removing the adjustable ocular disturbs the diopter adjustment. Use the fixed ocular as your reference for
36/DISASSEMBL Y & REPAIR
/
FOCUS KNOB
FIG. B41 Installing the objective-lens assembly. resetting the adjustable ocular-the to 0 diopter.
tIxed ocular is set
7. If the fixed ocular is ttu'eaded-and locked by a setscrew-the ocular can be adjusted. Removing the fixed ocular then disturbs the adjustment. On reassembly, screw in the fixed ocular to the O-diopter setting. Use the adjustable ocular-set to 0 diopter-to determine the O-diopter setting for the fixed ocular. Whenever you see a setscrew, use caution-the setscrew is probably locking an adjustable pUtt. Loosening the setscrew and turning the part disturbs an adjustment. 8. Removing the porro ptisms from the prism shelves will disturb adjustments. If the manufacturer uses the porro prisms for collimation, the cutouts in the prism shelves are noticeably larger than the pon'o prismsyou can then shift positions of the porro prisms. Note the adjusted positions of the pono prisms with respect to the cutouts. 9. If the porro prisms are used for collimation adjustments, dabs of hot wax or cement hold the porro prisms in the adjusted positions. Impact may cause the porro prisms to break loose from the cement. Align the pOlTO prisms with the cement dabs on reassembly-the collimation may then be correct without further adjustment.
SECTION C-ADJUSTING BINOCULARS A
•..
N
en
x
en
x
large percentage of the that come into the repair shop need onlybinoculars one thing-adjustment. The common complaint is, "I see two images" or, "The image isn't clear. "
oct:
oct:
...J
...J
c:(
c:(
xc:(
i= 0..
o
There are two optical adjustments that may bring binoculars into a repair shop--collimation and image tilt (or rotational error). Most other adjustments are only necessary if you've disassembled the binoculars.
u i= o
~
u
D-
...J oct:
U Z oct:
::c
U :i! w
COLLIMATION The most frequently required adjustment is collimation. If the binoculars are properly collimated, each optical axis aligns with the mechanical axis. The mechanical axis is the hinge pin, Fig. C 1. The optical axis of each side of the binoculars should then align with the hinge pin as shown in Fig. C 1. If the binoculars are out of collimation, you may see two images-one image from each side of the binoculars. After a moment, your eyes may compensate for the error. You then see only one image. But using the binoculars still results in eyestrain-and headaches. The collimation may appear conect when the binocular sides are fairly close together (small interpupillary distance). But when you spread the binocular halves (increase the interpupillary distance), you can see two images. The collimation becomes more critical as you increase the interpupillary distance. When you disassemble to make an adjustment-as when you're disassembling the binoculars for any other reason-remember to disassemble only one side at a time. You can then use the side you haven't disassembled as your standard. After you reassemble the one side, make the adjustments on that side-before you disassemble the other side. The reassembled/adjusted side now becomes your standard.
FIG. C1 In properly collimated binoculars, the two optical axes align with the mechanical axis.
r----------------, :
I
"TARGETS'
:
I
I I
I I
I
I
I
I
I
I
I I
I
LENS
LENS
I
I
I
L
~
CHECKING COLLIMATION Although there are special instruments available for checking collimation, most technicians simply use a visual check. The special instruments are expensive. Plus they can be difficult to obtain. We mentioned that each optical axis should align with the hinge pin. Fig. C2 shows a collimator-test fixture for aligning the optical axes to the mechanical axis. A clamp holds the binoculars by the hinge pin-the hinge pin is now perpendicular to the targets in the tester.
FIG. C2 A collimation-test
fixture.
ADJUSTING BINOCULARS/37
MOUNT TO HOLD BINOCULARS
TELESCOPE
SLIDE
FIG. C4
FIG. C3
Each target sits behind a lens. The distance between the lens and the target is equal to the focal length of the lens. As a result, the target appears to be at infinityan infinite distance away. And the light rays coming from the lenses are parallel, Fig. C2. Since the targets are at infinity, the optical axes of the objective lenses should be parallel to the hinge pin. If not, the targets as viewed through the binoculars appear off center. All you have to do is collimate each side individually to center the target.
~~~UMINATED
TARGET
FIG. C5 At left, the view when the binocular side is out of collimation. At right, the view when the side is properly collimated.
The actual tester may look more like Fig. C3. This tester uses two collimators to project the infinity targets. A collimator consists simply of an objective lens, a target placed at the focal point of the objective lens, and an illumination system for the target. The actual illuminated target projected by the collimator may be a crosshair or a special pattern, Fig. C5.
Since the image of the illuminated target passes through the binocular, it may be displaced by the binocular optics, Fig. C5 (left). But the reticle in the telescope always appears centered. The greater the collimation error, the fmther the illuminated target is displaced from the reticle.
A small telescope mounts on a slide at the other end of the tester, Fig. C3. As you look through the telescope, you see a reticle, Fig. C5-the reticle is inside the telescope.
In use, you just slide the telescope until you can sight through one side of the binoculars, Fig. C3. You then adjust that side until the projected target centers on the reticle, Fig. C5 (right).
38/ADJUSTING
BINOCULARS
Next you slide the telescope until you can sight through the other side of the binouclars, Fig. C4. And adjust that side until the projected target centers on the reticle. A variation of the tester uses a single collimator. The table that mounts the binouclars then slides, allowing you to align each side of the binouclars with the collimator. The tester shown in Fig. C3 may be too expensive for most independent shops-you would have to be repairing binoculars all day and every day to justify the expense. The fixture that holds the binoculars, lenses, and targets in alignment must be very precise. However, most visual techniques-and even the techniques with many test instruments-simply align one side of the binoculars with the other side. You can then use one side as your standard-generally the side you haven't disassembled. Align the optical axis of the other side with that of the standard side. Look through the binoculars to check for a second image. You should be able to readily detect if one image is higher than the other-your eyes normally can't compensate for up-down error. But your eyes may compensate for side-to-side erroryour eyes may actually cross slightly to merge the two images into one. By continuously blinking, however, you can defeat the compensating effect.
FIG C6 The image at the right is higher than the image at the left. But are you sure the image at the right is coming from the right-hand side of the binoculars? The images may be crossing over one another.
If you have a way to mount the binoculars in one spot, you can align the optical axes to the hinge pin. Aim the hinge pin at a distant target. A 6" ruler, placed on top of the hinge pin, can help as a sighting device. Then sight through each side of the binoculars in turn. The same target should center on each side of the binoculars. Here you're using a target that's effectively at infinity to simulate the tester shown in Fig. C4.
Or close one eye and center a distant target through one side of the binoculars. Then, without moving the binoculars, view through the other side with one eye. The same target should appear centered. By alternating eyes, you can also make certain which image is which. For example, suppose a tree appears as shown in Fig. C6 as you're viewing with both eyes. Here it seems that the image seen through the right side of the binoculars is slightly above and to the right of the image seen through the left side. But it's possible that the binoculars are so far out of collimation that the images cross-the image that appears to be from the right side may actually be from the left side. You may find that one side is so far out of collimation that you can only see through the other side. In that case, you don't know the direction that you have to move the errant image. Try moving the binocular sides closer together (decreasing the interpupillary distance) until you can see images through both sides. When you can see two images, you can determine which direction the one image must move.
FIG. C7 A V-block for holding the binoculars by the hinge pin. ADJUSTING BINOCULARS/39
For example, suppose that you aligned the hinge pin with the tree in Fig. C8. As you sight through the left side, you can see that the tree appears centered. The left side of the binoculars is then properly collimated. But as you sight through the right side, the tree appears off-center. The right side must now be collimated to center the tree. Using the technique shown in Fig. C8, there's no question as to which side is out of collimation--or as to the direction you must move the image. The main problem is in finding a way to secure the binoculars in one position-and still be able to sight on a target that's, in effect, at an infinite distance. It's actually easier to detect image correction if you keep your eyes around 6 inches behind the binoculars. You can then see the circles formed by the oculars as well as the images, Fig. C9. One technique is to sight on a horizontal line that's fairly close to the binocularsperhaps a window ledge at the other side of the room. The horizontal line should appear continuous as shown in Fig. C9. If the binoculars are out of collimation, the horizontal line on one side will be higher or lower, Fig. C 10. Here you're taking advantage of the fact that your eyes can't readil y compensate for up-down elTor.
/
\
FIG. C8 A test setup that simulates the binocular-collimator fixture. 40/ADJUSTING
BINOCULARS
FIG. C9 With your eyes around 6" behind the oculars, you see two circles. The continuous horizontal line indicates proper collimation.
FIG. C10 The broken horizontal line tells you the binoculars are out of collimation.
Also check collimation at different interpupillary distances. The collimation may appear acceptable if the binocular sides are close together. But when you increase the interpupillary distance, you can see the images separate. Some factory testers also ignore the mechanical axis and simply align one optical axis with the other optical axis. Fig. Cll and Fig. C12 show a hand-held collimating tool that allows you use one eye and see the image formed by each side of the binoculars.
FIG. C11 A hand-held collimating tool.
Since you're only using one eye, your eyes can't compensate for an error. A properly collimated pair of binoculars shows only one image-the two separate images merge. But if the binoculars are out of collimation, you see two images. The two images are slightly different in color. You can then note which direction you must move the image on one side. The tool uses a pair of prisms to provide the two images, Fig. C 13. You look directly through one prism to see through one side of the binoculars-the prism you're looking directly through has a yellowish or pinkish hue, giving the image a light tint. The image from the other side of the binoculars goes through the long prism and reflects from the 4Y surface to the eyepiece. When you're holding the tool as shown in Fig. C12, the tinted image is coming from the right-hand side of the binoculars. The white image is coming from the left-hand side. You then adjust one side of the binoculars until the two images superimpose. Again you're just adjusting the optical axis of one side to match the optical axis of the other side.
EVELENS
FIG. C12
The tool does offer a big advantage over visual techniques. Since the images are different in color, you know which image is coming from which side. So, if the images actually cross over one another, there's no confusion. Perhaps the tinted image appears to the left of the white image. You then know that the images are crossing over one another. If you're repairing binoculars professionally, you can probably justify the cost of the tool shown in Fig. C 11. You might check with binocular manufacturers for the tool availability and cost. The special tools for checking collimation require little practice to use. The tool shown in Fig. Cll makes it readily apparent which way you must move either image. Visual techniques, however, do require some practice. Normally you want to note the direction you need to move one image. Then make an adjustment and check your results. Unless you have a way to mount the binoculars in a stationary position, it's very difficult to
"" PRISM PAIR
LIGHT PATH
v
"'"
EVELENS
/
TINTED PRISM
FIG. C13 Prisms in collimating tool. ADJUSTING BINOCULARS/41
watch the image movement while you're making the adjustment. There are four types of collimation find in binoculars-objective-Iens lens adjustments, porro-prism prism-shelf adjustments. A pair mally has one of the four types.
ECCENTRIC ECCENTRIC
RING
LENS MOUNT
adjustments you'll adjustments, eyeadjustments, and of binoculars nor-
What would cause binoculars to be out of collimation? Impact is a common culprit. If the binocular uses the porro prisms for adjustment, each porro prism is locked in place with dabs of cement. Impact can break loose the cement and cause the porro prism to shift. Loose screws can also cause the problem. Perhaps the binoculars use the objective lenses for adjustment. If the screws holding the prism shelves work loose, the porro prisms can tilt. You may then be able to adjust the collimation with the objective lenses. But unless you tighten the loose screws, the binoculars won't stay in adjustment.
FIG. C14 Two eccentric rings used to position the objective lens. OBJECTIVE-LENS
\
CELL
ECCENTRIC
RING
OBJECTIVE-LENS ADJUSTMENTS In many binocular designs, eccentric rings position the objective lenses, Fig. C14. An eccentric ring fits over the shoulder at the front of the objective-lens cell, Fig. C15. The lens-cell shoulder is also an eccentric. ECCENTRIC
Turning the eccentric rings allows you to shift the optical axes of the objective lenses. Remember that you're viewing the image after that image has passed through the erecting system. You then shift the objective lens in the opposite direction that you want the image to move.
SHOULDER
FIG. C15 Side view of the objective-lens cell.
For example, in Fig. C16 the left binocular side is properly collimated-it aligns with the hinge pin. But the right binocular side is out of collimation. Here you want to adjust the right-side image- move the image from right to left. If you're looking through the binoculars, you must then shift the right-side objective lens to your light. Or, if you're looking at the front of the objective lens, Fig. C14, shift the objective lens to your left. Similarly, if the image is too high, shift up the objective lens-moving up the objective lens moves down the image. Shifting the objective lens a slight distance moves thc image a relatively large distance. To reach the objective-lens adjustment, remove the decorator cap at the front of the objective-lens tube, Fig. C17. Usually the decorator cap unscrews-hold the objective-lens tube as you unscrew the decorator cap (the objective-lens tube also screws into place). But
421ADJUSTING BINOCULARS
BACK VIEW OF RIGHT-SIDE OBJECTIVE LENS
FIG. C16
if the decorator cap is rubber, it may simply lift off. You'll then see a retaining ring around the objective lens, Fig. C17. The retaining ring both holds the objective lens in place and locks the adjustment on the eccentric ring.
FRONT VIEW
If you completely remove the retaining ring, you can lift out the eccentric ring and the objective-lens cell. But, for adjustment purposes, you may only have to loosen the retaining ring.
DECORATOR
:J RETAINING
_~~~~~~/~"'3
You can see the eccentric rings without removing the retaining ring. Each eccentric ring may have spanner notches, Fig. CI8. The inner ring is the eccentric lens mount; the outer ring is the free-turning eccentric ring. You can use the spanner notches to hold one eccentric ring stationary as you turn the other eccentric ring. The tool shown in Fig. CI9 was designed for turning the eccentric rings independently of one another. The tool consists of two tubes. Each tube has tips at one end to fit the notches of the eccentric rings.
RING
SIDE VIEW
FIG. C17 Disassembly to reach the objective lens.
In use, you simply slip the smaller tube inside the larger tube, Fig. CI9 . You can now use the tool to engage both eccentric rings simultaneously. Hold the smaller tube and turn the larger tube to rotate the outer eccentric ring. Or hold the larger tube and turn the smaller tube to turn the inner eccentric ring. Since the tool is tubular, you can view through the binoculars while you're making the adjustment (pro-
FIG. C18 Each eccentric ring may have spanner notches. The inner notches are on the objective-lens mount. ADJUSTING BINOCULARS/43
viding you can find a way to hold the binoculars stationary). You can then watch the image shift as you rotate the eccentric rings. The tool shown in Fig. C19 may not be a practical investment for most shops. For one thing, the tool fits only one size. Plus, in most binoculars, the objectivelens mount does not have spanner notches-only the eccentric ring has spanner notches. It's then only necessary to loosen the retaining ring, Fig. C20-you can reach the notches in the eccentric ring by working under the retaining ring. To turn the eccentric ring, use a tool that won't cause damage if it slips-for example, a sharpened piece of pegwood. Insert the tool into one eccentric-ring notch. Then turn the eccentric ring to shift the optical axis of the objective lens. Here you can't watch the image move as you make the adjustment. You should first make a mental note as to which direction you want to move the image. Then, working from the front of the binoculars, turn the eccentric ring to move the objective lens in the desired direction.
FIG. C19 A special tool for adjusting the eccentric rings-separated at left and assembled at right. ECCENTRIC
RING
For example, Fig. C21 A shows the objective lens centered-the thickest part of the eccentric ring aligns with the thinnest part of the eccentric lens-cell shoulder. To shift the objective lens the maximum distance to the right, you can hold the lens cell and turn the eccentric ring 180· -to the position shown in Fig. C2lB. Now the thickest part of the eccentric ring aligns with the thickest part of the lens-mount shoulder. Or perhaps the eccentric rings are in the positions shown in Fig. C21B. And you want to shift up the objective lens the maximum distance. You can then turn both eccentric rings 90° in a counterclockwise direction. Shifting up the objective lens, you11 recall, moves down the image.
FIG. C20 You can see the eccentric ring under the retaining ring. Here the eccentric ring has only one notch.
Normally you don't need to move the objective lens the maximum distance-a small amount of objectivelens movement results in a relatively large amount of image movement. And you're generally adjusting one side of the binoculars (the side you've disassembled) to match the other side (the side that's your standard). Very little movement of the objective lens should then be required.
A Since you normally need so little objective-lens movement, technicians sometimes try a shortcut. Remember from Section B that the rotational position of the objective-lens tube can also affect collimation-providing the binoculars use eccentric adjustments on the objective lenses. Turning the complete objective-lens
44/ADJUSTING
BINOCULARS
8
FIG. C21 In A, the objective lens is centered by the eccentric rings. In B, the objective lens has been moved the maximum distance to the right.
tube shifts the position of the objective lens-just as turning the eccentric ring shifts the objective lens. In Section B, we stressed returning the objective-lens tube to its original position. But, if you have to adjust the collimation, you might try turning the objectivelens tube. Adding a slight amount of torque to screw in the objective-lens tube a little further-or backing out the objective-lens tube slightly-may provide sufficient movement.
--
B
A
You can obtain very little adjustment by turning the objective-lens tube. Trying to overtighten the objective-lens tube could damage the threads. And you can only back out the objective-lens tube a slight distance before it's loose. In most cases, you would probably only turn the objective-lens tube to fine-tune your objective-lens adjustments.
EYELENS ADJUSTMENTS Section B also mentions the eyelens adjustments found in some binoculars. Remember that the eyelens may use an eccentric ring. The eyelens cell then has an eccentric shoulder-like the eccentric shoulder on the objective-lens cell just discussed. And, like the objective-lens eccentric ring, an eccentric ring fits around the eyelens-cell shoulder.
FIG. C22 Turning out setscrews C and B equal amounts-and turning in setscrew A-moves the eyelens in the arrowmarked direction. Or you could loosen B slightly more than you loosen C. Then, as you turn in A, the eyelens shifts to the right and up.
Or three setscrews may position the eyelens cell, Fig. C22; a fourth setscrew from the top normally locks the adjustment. You can then shift the eyelens by loosening and tightening setscrews. For example, suppose that you want to move the eyelens to the right in Fig. C22-the direction shown by the arrow. You can then loosen setscrews C and D in equal amounts. Turn in setscrew A to push the eyelens to the right-against setscrews C and D.
A
Or perhaps you want to move the eyelens at an angle as shown by the arrow in Fig. C23. You could then loosen setscrew B. Turn in setscrews A and C. Not many binoculars use adjustments on the eyelens. But if the eyelens is adjustable, the collimation procedures are the same as we've already described for the objective lens. The only difference-you're making the adjustments on the eyelens. You can spot an adjustable eyelens after removing the eyecup-you should be able to see the eccentric ring under the retaining ring. Or, if the eyelens uses setscrew adjustments, you can see the setscrews around the outer circumference of the ocular-and probably a locking setscrew at the top of the eyelens cell.
FIG. C23 Turning out setscrew B-and turning in setscrews A and C-moves the eyelens in the arrowmarked direction.
ADJUSTING BINOCULARS/45
FIG. C24 Setscrews used to tilt the porro prisms on the objective side. Another pair of setscrews tilts the porro prisms on the ocular side. PORRO-PRISM ADJUSTMENTS Many binoculars provide no adjustments on the objective lenses. To collimate the binoculars, it's necessary to shift the pono prisms. And reaching the pono prisms for adjustment requires partial disassembly of the binoculars. Remember that each side of the binoculars has two pOlTa prisms. The prisms fit on the prism shelf in the binocular body, Fig. C24. If you remove the prism cover on the objective-lens side, you can see the porro prism on one side of the shelf, Fig. C24. If you remove the prism cover on the ocular side, you can see the porro prism on the other side of the shelf. You've seen that each porro prism sits within a cutout in the prism shelf. The cutout matches the shape of the porro prism-but the cutout is larger than the porro prism. In binoculars designed for objective-lens adjustment, the cutout may be only slightly larger than the porro prism; the porro prism then fits snugly within the cutout. But if the binoculars were designed for prism adjustment, the cutout may be quite a bit longer than the pono prism. It's then possible to shift the porro prism within the cutout. A prism clamp across the top of the pono prism, Fig. C24, secures the adjusted position. The prism clamp may be held by screws. Or each end of the prism clamp may simply slide into a slot in the binocular body. In binoculars designed for prism adjustments, each pono prism is also cemented in its adjusted position. Dabs of cement or hot wax hold the pono prism.
46/ADJUSTING
BINOCULARS
After removing the cement-and possibly loosening the prism clamp-you can shift the porro prism within the cutout. Sliding the porro prism as shown by the double-ended arrow in Fig. C25 shifts the image position for collimation. TIlting the porro prism also shifts the image position. TIlting the porro prism may require using shims-thin pieces of metal or paper-to hold the adjusted position. But many binoculars-especially higher quality binoculars-have setscrew adjustments, Fig. C24. You can then tilt the prism by turning the setscrew. If you see a setscrew, Fig. C24, reach the screw slot from the outside of the binocular body. You may be able to see the screw slot. Or you may have to remove a decorator disc or peel back the leatherlike body covering to reach the screw slot.
FIG. C25 To move the image as shown by the double-ended arrow, shift the porro prism in the same direction
The positions of the porro prisms, however, affect more than the collimation-they also affect the rotational position of the image. Each porro prism must be at a 90° angle to its mate, Fig. C26. If the angle is greater or less than 90°, the image appears tilted, Fig. C27B. Check the image tilt by viewing a horizontal linesuch as the top edge of a fence-through the binoculars. View through each binocular side in turn. If the image through one side appears tilted, the porro prisms on that side aren't at a perfect 90° angle. The porro prisms, then, affect two critical adjustmentscollimation and rotational error. That's why you should avoid disturbing the porro-prism positions. But when you do have to adjust the porro prisms, use the porro prism at the front of the binocular side (the porro prism closer to the objective) to adjust for rotational error. Use the porro prism at the back of the binocular side (closer to the eyelens) to adjust collimation.
FIG. C26 The angle between the porro prisms should be 90°.
A
ADJUSTING ROTATIONAL ERROR WITH THE PORRO PRISMS If the problem with the binoculars is rotational error, you need only adjust the front porro prism. With most binoculars, unscrew the complete objective-lens tube, Fig. C29-the objective-lens tube screws into the binocular body (but, if the binoculars use objective-lens collimation adjustments, remember to mark the position of the objective-lens tube). Then remove the prismcover plate at the front of the body. Usually, one or two screws hold the cover plate. But you may find that the cover plate simply lifts off after you remove the objective-lens tube. You can now reach the front porro prism, Fig. C28. If there's cement or wax holding the porro prism at the comers, Fig. C28, carefully remove the cement. And, if the clamp is held by screws, it may be necessary to loosen the prism-clamp screws. You can then shift the porro prism to adjust the angle.
8 FIG. C27 The view of a horizontal line in A shows no rotational error. B shows rotational error on the right side. FRONT PORRO PRISM
Check the image tilt without replacing the cover platejust screw the objective-lens tube into the binocular body. Once you've shifted the porro prism to the proper angle, check collimation-remember that sliding the porro prism will affect the image position. If the binocular body and the objective-lens tube are one piece, it's more difficult to reach the front porro prism. The prism shelf is a separate part. Reaching the front porro prism then requires removing the prism shelf from the ocular side.
FACE OF REAR PORRO PRISM
FIG. C28 Shift the end of the front porro prism as indicated by the double-ended arrow to correct rotational error. ADJUSTING BINOCULARS/47
You can then reach the front porro prism to shift its angle. But to check the results of your adjustment, you must replace the prism shelf.
ADJUSTING THE PORRO PRISM FOR COLLIMATION If you have to collimate the binoculars-and there's no eccentric ring on the objective lens- shift the rear porro prism. Unfortunately, the rear porro prisms are often harder to reach than the front porro prisms-you may have to remove the oculars. In Section B, Disassembly & Repair Techniques, you saw that you can usually remove the two oculars as an assembly. You may prefer to remove the two oculars together with the hinge pin, Fig. C29-just unscrew the hinge-adjusting screw at the front of the binoculars. But, as you'll recall, you may then lose the hingepressure adjustment. You can avoid disturbing the hingepressure adjustment by unscrewing the ocular shaft from the focus knob as described in Section B. Reach the porro prism by removing the rear-prism cover, Fig. C29. Like the front-prism cover, the rear-prism cover is normally held by screws. You may also have to unscrew one of the ocular tubes, Fig. C29-the metal tube that passes inside the ocular. Now check the rear porro prism-there may be an obvious reason why the binoculars are out of collimation. If the binoculars were dropped, the porro prism may have broken loose from its cement. In that case, as you'll recall, it may only be necessary to realign the porro prism. Use the dabs of cement as your guides. Part of each cement dab may have remained with the prism shelf-and the other part of each cement dab may have remained with the porro prism. Shift the porro prism until the sections of the cement dabs align.
FIG. C29 Sliding out the ocular assembly. cover plates. You can then reach the porro prismseither to recement the porro prisms or to adjust the positions. If you do have to adjust the collimation, note ifthere's a setscrew to control the tilt. You can then reach the setscrew from the outside of the binocular body-but, as mentioned earlier, you may have to peel aside the leatherlike body covering to locate the slot of the setscrew. The end of the setscrew comes against the upper end of the porro prism-the position of the arrow in Fig. C30. The spring action of the prism clamp then holds the porro plism against the setscrew.
Or the entire dab of cement may have remained with the prism shelf. But you can still see an outline of the cement dabs on the sides of the porro prism. Just align the cement dabs with the outlines. In many cases, shifting the porro prism to align the cement dabs corrects the collimation. Also check the other porro prisms-if one porro prism broke loose, there's a good chance the other porro prisms broke loose as well. Before recementing the porro prisms, reassemble the binoculars and check collimation. Remember that you can often reassemble the binoculars without the prism-
48/ADJUSTING
BINOCULARS
FIG. C30 The setscrew comes against the top of the porro prism (arrowmarked position).
TIlting the porro prism moves the image as shown by the double-ended arrow in Fig. C31. For example, say you turn in the setscrew (screw-tightening direction). The image then moves in the A direction, Fig. C31. The spring action of the prism clamp allows the porro prism to tilt. If you back out the setscrew (screw-loosening direction), the image moves in the B direction, Fig. C31. Now the spring action of the prism clamp pushes the porro prism against the end of the setscrew. Sliding the porro prism moves the image as shown by the double-ended arrow in Fig. C32 (A and B). Slide
A~B
the porro prism in the same direction as you want the image to move. You normally can't watch the image movement as you're adjusting the porro prism. First check the collimation and note which direction you must move the image. If you want to move the image as shown by the double-
REAR PORRO PRISM ON LEFT SIDE
FIG. C31 Image movement from tilting the porro prism.
REAR PORRO PRISM ON RIGHT SIDE
SLIDING ADJUSTMENT
A B
----------------L--------------TILTING ADJUSTMENT
C
o
FIG. C32 The double-ended arrows indicate the direction the image can be moved with the adjustments shown. ADJUSTING BINOCULARS/49
ended arrow in Fig. C31, you know you must tilt the porro prism. Or, if you want to move the image as shown by the double-ended arrows by the top drawings in Fig. C32, you know you must slide the porro prism. Disassemble the binoculars as far as necessary to reach the porro-prism adjustments. Make the adjustment. Then temporarily reassemble the binoculars just far enough to check the effect of your adjustment. For example, consider in Fig. C33 that the images do not cross-the tree appearing at the right is the image viewed through the right-hand side, and the tree appearing at the left is the image viewed through the lefthand side. Here we're holding the binoculars with the left-hand image centered. But, unless you're aligning the optical axes with the mechanical axis, you don't know which side should be centered and which side should be adjusted.
FIG. C33
B
Let's say you've just worked on the right-hand side. You then know you want to move the right-side image slightly down and to the right. From Fig. C34B, you can see that you can tilt the right-side porro prism to move the image in the desired direction. Thrn in the setscrew to move the image in the direction of the arrow, Fig. C34B. Or perhaps you've repaired the left-hand side. You can then move the right-hand image up and to the right by sliding the left-side porro prism. Move the left-side porro prism as shown in A of Fig. C34.
FIG. C34
As another example, perhaps you see the result shown in Fig. C35. And you've repaired the right-hand side. You want to move the right-side image slightly up and to the left. You can now slide the right-side porro prism as shown in B of Fig. C36. Remember, slide the porro prism in the same direction as you want the image to move. Whatifyou want to move the left-side image? You can tilt the left-side porro prism by turning in the setscrew as shown in A of Fig. C36.
FIG. C35
PRISM-SHELF ADJUSTMENTS If the prism shelf is a separate part (as opposed to being built into the binocular body), it may be adjustable. Look for adjustment screws next to the prism-shelf screws, Fig. C37. You can easily recognize an adjustment screw-an adjustment screw appears to be a screw that hasn't been fully tightened. One end of each adjustment screw comes against the binocular body, Fig. C38. Turning in the adjustment
50/ADJUSTING
BINOCULARS
FIG. C36
screw then tilts the prism shelf-and thereby the porro prisms-in one direction. Turning out the adjustment screw-and then tightening the prism-shelf screwtilts the prism shelf in the other direction. Some binoculars may have only two adjustment screws. But most adjustable prism shelves have three adjustment screws--one by each prism-shelf screw. Tilt the prism shelf in the same direction as you want the image to move. For example, say that you want to move the image from left to right-the direction of the arrow in Fig. C39. You can then turn in adjustment screw A (the screwtightening direction). Slightly loosen the three prismshelf screws. Then turn in adjustment screw A. Finally, retighten the three prism-shelf screws.
FIG. C37
Recheck the adjustment after you tighten the prismshelf screws. TIghtening the screws may cause the image to shift. Or you may want to move the image from right to leftthe direction of arrow #1 in Fig. C40. Turn out adjustment screw A (the screw-loosening direction). Then turn down the prism-shelf screw indicated in Fig. C40. Moving the image at an angle may require turning in one adjustment screw and turning out another adjustment screw. Perhaps you want to move the image in the direction of arrow #2 in Fig. C40. You can do so by turning out adjustment screw B. Then turn in adjustment screws A and C
BODY
FIG. C38 Side view of the adjustment screw.
ADJUSTMENT
FIG. C39
SCREW A
PRISM-SHELF
SCREW
C
FIG. C40 ADJUSTING
BINOCULARS/51
521ADJUSTING BINOCULARS
Fig. C41 shows some more examples of how you can move the image in the arrowmarked direction. You can change the angle of image movement by turning in (or out) a pair of screws different amounts. For example, in the top drawing of Fig. C41you can turn in adjustment screws Band C equal amounts to move the image in the arrowmarked direction. Or you can turn in adjustment screws B and C different amounts to change the angle of image movement. If you want to turn the arrow slightly counterclockwise, turn in adjustment screw C slightly more than adjustment screw B. Remember to loosen the prism-shelf screws before you turn in an adjustment screw. And tighten the prismshelf screws after you turn out an adjustment screw.
from around 80 feet to
00.
You'll recall that the light rays from an 00 subject are parallel to one another, Fig. C42 (top). But if the subject is closer than 00, the light rays diverge, Fig. C42 (bottom). The objective lens then brings the light rays together at a point behind the 00 focal point. The closer the subject, the more the incident light rays divergeand the further the light rays come together behind the objective. The focal point of the ocular in Fig. C42 (bottom) is now to the front of the focal point of the objective lens. As a result, the image appears out of focus. To focus the binoculars, you must move the oculars away from the objective lenses.
ADJUSTING FOCUS You'll see a focus error when you can't bring the focal point of the oculars to the same position as the focal point of the objectives. The problem is usually in the oculars. In Section B, you saw the adjustments on the oculars. Normally adjustment is only necessary if you've disassembled and reassembled the oculars. However, you may find that the setscrews holding the adjustable control knob have come loose. The control knob then slips, losing the diopter adjustment. Refer to Disassembly of the oculars in Section B for the adjustment procedure. You may also encounter a focus error if you've disassembled and reassembled a focus-knob assembly. If you've reassembled the ocular shaft with the focus knob in the wrong position, you may not be able to focus the binoculars throughout the full range. You may find that you can focus on close subjects. But you can't focus on distant subjects--or vice versa. Typically 7X binoculars should focus from around 40 feet to 00. With greater magnification, you normally can't focus as close. A lOX binocular typically focuses
If you can't focus at a close enough distance, the oculars aren't moving far enough away from the binocular bodies. It may then be necessary to again disengage the ocular shaft from the focus knob. Thrn out the focus knob to move it further from the hinge pin. Then restart the threads of the ocular shaft. Or perhaps you can focus at a sufficiently close distance-but you can't focus at 00. In that case, the oculars aren't moving close enough to the binocular bodies. Again you may have to disengage the threads of the ocular shaft from the focus knob. Turn in the focus knob to move it closer to the hinge pin. Then restart the threads of the ocular shaft. How far you screw the focus knob in or out qepends on the amount of error. It may require several tries to adjust the focus. You can now see why we stressed noting the focus-knob position when the threads of the ocular shaft disengage.
OTHER ADJUSTMENTS The other adjustments FOCAL POINT AT
INCIDENT LIGHT RAYS AT
I
are normally only necessary 00
OCULAR
00
OBJECTIVE FOCAL POINT AT FINITE DISTANCE INCIDENT LIGHT RAYS AT FINITE DISTANCE
FIG. C42 ADJUSTING BINOCULARS/53
when you disassemble the binoculars. We described the hinge-pressure adjustment in Section B. Remember that the hinge-pressure adjustment is normally the screw at the end of the hinge. The adjusting screw often has a setscrew to lock the adjustment. After loosening the setscrew, you can turn the adjusting screwturn in the adjusting screw to increase the hinge pressure, turn out the adjusting screw to decrease the hinge pressure. If you can't adjust the hinge pressure with the screw, the adjustment may require adding or removing washers. The washers are between the two binocular sides at the hinge positions. Another adjustment you may disturb during disassembly is the position of the IPD scale. Remember that it's relatively easy to reset the IPD scale. Just set the IPD scale until the number shown is the distance between the optical centers of the eyelenses. If the binoculars have a reticle, there's another adjustment you can disturb-the pOSition of the reticle, Fig. C43. The reticle normally mounts in a tube that screws into the prism shelf. A retaining ring at the top of the tube secures the reticle. If you loosen the retaining ring, you can turn the reticle to change its rotational position. On reassembly, turn the reticle until its horizontal and vertical graduations appear visually correct. Then replace the eyelens assembly and check the alignment. A horizontal graduation on the reticle should align with a horizontal line in the target you're viewing. Or check the vertical graduation against a vertical line in the field. Chances are you'll have to remove the ocular assembly, loosen the reticle retaining ring, and rotate the reticle slightly. Replace the ocular assembly and again check the alignment. You may need several tries before the reticle aligns with horizontal and vertical lines in the field. Occasionally you may get the complaint that the reticule is out of focus. When you adjust the ocular for a sharp image of the subject, the reticle graduations aren't sharp. Remember that the reticle sits at the focal point of the objective lens. If the reticle isn't sharp when the image is sharp, it isn't sitting at the focal point. Chances are the reticle tube or the reticle retaining ring has worked loose.
SUMMARY OF OPTICAL ADJUSTMENTS You're normally
54/ADJUSTING
only concerned
with two adjust-
BINOCULARS
ALIGN THE VERTICAL RETICLE WITH A VERTICAL LINE IN THE SUBJECT...
...OR THE HORIZONTAL RETICLE WITH A HORIZONTAL LINE IN THE SUBJECT
FIG. C43 Aligning the reticle. ments-collimation and rotational enor (image tilt). For rotational error, use the front pono prism-the pono prism closer to the objective lens. Turn the porro prism to set a 90° angle between the two pono prisms. Typically a pair of binoculars has one of the following adjustments for collimation: 1. the objective lens. Unscrew the cap from the front of the objective lens-but don't unscrew the retaining ring that holds the objective lens. By looking at the front of the objective lens, you can see if an eccentric ring is used. You can see the eccentric ring under the retaining ring. Move the objective lens in the opposite direction to desired image movement. Some binoculars have the collimation adjustments on the eyelenses rather than on the objective lenses. 2. the rear porro prism. If there's no eccentric on the objective lens, the collimation adjustment may require shifting the rear pOlTOprism (the porro prism on the ocular side). The pOlTOpIism is then held in its adjusted position by dabs of cement. Slide the pOlTOprism to move the image in one direction, Fig. C32 A & B. Tilt the pono prism to move the image in the other direction, Fig. C32 C & D. Some binoculars use setscrews to tilt the porro prisms; you can then reach the setscrews from the outside of the binocular body. Slide or tilt the porro prism in the same direction as you want the image to move. 3. the prism shelf. If the binoculars use separate prism shelves (rather than prism shelves that are built into the bodies of the binoculars), each pIism shelf may be adjustable. Look for adjustment screws on the prism shelves. Most adjustable prism shelves have three adjustment screws. Some have only two adjustment screws. Use the adjustment screws to tilt the prism shelf in the same direction as you wan t the image to move.
SECTION D-ZOOM BINOCULARS Zoom allow As youyou to move changethethezoom magnificationbinoculars of the oculars. control, optical elements move within each ocular. The principle is similar to the zoom lenses used with cameras-the magnification increases or decreases as the optics move. To zoom the binoculars shown in Fig. DI, move the zoom lever. A scale under the fixed ocular shows the actual magnification you've set, Fig. D2. In some zoom binoculars, the magnification scale is under the zoom lever. Moving the zoom lever moves the optics within the adjustable ocular. A gear system connects the optics inside the adjustable ocular to the movable optics inside the fixed ocular. Not all zoom binoculars use a gear system to couple the two oculars; you'll see other coupling systems in this section.
FIG. 01
But regardless of the coupling system, one ocular acts as the master-it's directly adjusted by the zoom lever. The other ocular acts as the slave. The master turns the slave through the coupling system. In many systems, it's necessary to time the slave to the master. The two oculars then have the same magnification.
OPERATION OF THE ZOOM LENS A zoom lens is a combination of two lenses-a prime lens with a fixed focal length and a variable-power supplementary lens. The supplementary lens uses movable elements to change the focal length. In an ocular, the prime lens is the eyelens-the eyelens stays in the same position during the zoom. The variable-power supplementary lens then sits in front of the eyelens. Fig. D3 shows the optics in a varifocallens-a lens that allows you to change the focal length while shifting the focal point. The zooming element, Fig. D3, moves along the axis to change the focal length. When the zooming element is as far back as it can go, Fig. D3A, the lens is at the longest focal length. Moving the zooming element all the way forward, Fig. D3B, provides the shortest focal length. Although the lens shown in Fig. D3 changes the magnification during zoom, it also changes the focus. Most zoom lenses compensate for the different focal length to maintain the focus. The lens must add another moving component-the compensating element.
FIG. 02
--(j]-A-MAXIMUM
FOCAL
LENGTH
--(1]-B-MINIMUM
FOCAL
LENGTH
FIG. 03 ZOOM BINOCULARS/55
There are two types of focus compensation used in zoom lenses: optical compensation and mechanical compensation. Fig. D4 shows an optically compensated zoom lens. Elements 1 and 3 are coupled together. As you zoom the lens, both elements move as shown in Fig. D4. But most zoom lenses systems. Here both the pensating element are move the elements at different directions-as
use mechanically compensated zooming element and the compositioned by cams. The cams different speeds-and often in you change the focal length.
Fig. D5 shows the zooming element and the compensating element in a zoom ocular. The eyelens serves as the prime lens-it doesn't change position during the zoom. But the eyelens in the adjustable ocular does move when you change the diopter setting. In zoom binoculars, you still set the focus with the focus knob and the adjustable ocular. The ocular is then focused at the focal point of the objective lens. As you now zoom the ocular, the zooming element moves as shown in Fig. D5. The magnification of the oculardetermined by the zooming element and the eyelenschanges.
~E-~ a-ilD
A cam tube holds both the zooming element and the compensating element, Fig. D6. The screws that hold the movable elements inside the cam tube also serve as cam followers-the screwheads ride within the cam slots in the cam tube, Fig. D6. Notice in Fig. D6 that the cam slots are different. A straight carn slot moves the zooming element. Since the cam slot is straight, the movement of the zooming
56JZOOM BINOCULARS
CD
FIG. 04 An optically compensated zoom lens. EYELENS
COMPENSATING ELEMENT
ZOOMING ELEMENT FOCAL POINT
A-MAXIMUM
Setting a lower magnification increases the separation between the zooming component and the eyelens, Fig. D5B. If it weren't for the compensating element, the focal point of the ocular would also change. But, as you can see in Fig. D5, the compensating element moves toward the zooming component. The compensating element then shifts the focal point of the ocular. The focal point remains in the same position as you zoom the ocular, Fig. D5-the position you determined when you focused the binoculars. The movement of the zooming element is linear-the separation between the zooming element and the eyelens changes the same amount for an equal amount of magnification change. But the movement of the compensating elementis nonlinear-equal amounts of magnification change do not result in equal amounts of movement. The mechanical cams set the positions of the two movable elements and determine the movement rate.
CD
B-MINIMUM
FIG.05 ocular.
MAGNIFICATION
MAGNIFICATION
A mechanically coupled zoom
CAM SLOT FOR COMPENSATING ELEMENT
CAM SLOT FOR ZOOMING ELEMENT \
EYELENS
FOLLOWER SCREWS
FIG. 06 The cam tube holds the two movable elements.
element is linear. But a curved cam slot moves the compensating element. The curved carn slot provides the nonlinear movement. Also notice that the cam slots run in opposite directions. As the zooming element moves toward the front of the carn tube, the compensating element moves toward the back of the cam tube. You can remove the elements from the carn tube by taking out the follower screws. The compensating element slides out toward the back of the cam tube; the zooming element slides out toward the front (eyelens end) of the cam tube, Fig. 07. Fig. 08 shows how the optics move within the cam tube. The eyelens for the fixed ocular doesn't move; the eyelens for the adjustable ocular moves only when you change the diopter setting. With the an ocular set at maximum magnification, the lens cells are in the positions shown in Fig. 08A. The zooming element is all the way to the back of the cam tube. And the compensating element is all to way to the front of the cam tube. There is now maximum separation between the elements. Setting a lower magnification rotates the carn tube counterclockwise as seen from the eyelens end. Now the zooming element moves toward the back of the carn tube. And the compensating element moves toward the front of the cam tube, Fig. D8B. At the lowest magnification, there's the minimum separation between the compensating element and the zooming element.
A-MAXIMUM
LENS CELL WITH ZOOMING ELEMENT
LENS CELL WITH COMPENSATING ELEMENT
FIG.07
The lens cells removed from the
earn tube.
Changing the separation between the zooming element and the eyelens changes the magnification. Without the compensating element, the focal point would also change. But the movement of the compensating element holds the focal point at the same position. The carn tubes for each ocular fit inside the zoom tubes, Fig. 09 and Fig. OlO-there's one zoom tube inside each ocular. As you turn the zoom lever, the zoom tubes rotate. The zoom tubes then turn the cam tubes. With the design shown in Fig. D9, a notch in the carn tube keys over a screwhead on the zoom tube. So, as the
'"
MAGNIFICATION
LENS CELL WITH ZOOMING ELEMENT
LENS CELL WITH COMPENSATING ELEMENT
/B-MINIMUM
MAGNIFICATION
FIG. 08 ZOOM BINOCULARS/57
zoom tube rotates, it carries the cam tube in the same direction. But the zooming element and the compensating element do not rotate-the elements move along straight lines. The guide slots in the ocular tubes, Fig. Dll, prevent the elements from rotating. The screwheads on the lens cells-the same screwheads that ride within the cam slots-fit into the guide slots. As the cam tubes rotate, the cam slots move the elements in or out. The cam slots then determine the direction and the rate that the elements move.
NOTCH THAT FITS OVER SCREWHEAD ON ZOOM RING
" FIG. 09 earn tube "
removed.
,
Damage to the cam tube may result in another malfunction-the focus may shift as you zoom. Once you've set the focus for your own eyesight and the focus distance, the focus should remain sharp as you change the magnification. But if the cam tube is damaged, the image may shift out of focus. The design shown in Fig. D12 uses gear coupling to connect the master zoom
FIG. 010 Zoom tube removed.
CAM SLOT ZOOMING ELEMENT
\1-----\
\
\
\
\
CAM TUBES OCULAR TUBES
\
\
\
\
\
\
",.
\ \~ "-
FIG. 011
Cam tubes removed from binoculars.
58/Z00M
BINOCULARS
_ CAM SLOT FOR COMPENSATING ELEMENT
COUPLING GEAR
SCALE FOR INTERPUPILLARY DISTANCE
FIXED OCULA
RETAINING RING
FIG. 012
lOOM-LEVER RING
Underside of binoculars. ZOOM TUBE
tube to the slave zoom tube. The bottom shoulder of the zoom tube in Fig. D13 is threaded-a large zoom-tube gear screws onto the threaded shoulder. The zoom-lever ring, Fig. DB, also screws over the threaded zoomtube shoulder-the zoom-tube gear is under the zoom-lever ring in Fig. D14. A retaining ring screws over the zoom-tube gear at the bottom of the slave zoom tube, Fig. D14. The two intermediate gears, Fig. D14 , engage the zoom-tube gears. And the coupling gear, Fig. D 11, engages the two intermediate gears to complete the gear train.
THREADED SHOULDER
lOOM-
IIIIIIIIIIIIIIIIIIIIIIIIIIIII/~~~~
/
1IIIiWIIIIIIIIIIIIIIIIMlIIlIIlIIlIIlII~;jJIIIIIIIIIIIIIIII~III1~
Moving the zoom lever turns the master zoom tube-the zoom-lever ring connects directly to the master zoom tube. The zoom-tube gear on the lower shoulder of the master zoom tube then turns the intermediate gear. Now the coupling gear, Fig. D11, turns the other intermediate gear to rotate the slave zoom tube.
lOOM-LEVER RING (OR RETAINING RING)
FIG. 013
When you reassemble the binoculars, it's necessary to time the gears
RETAINING RING
FIG. 014 Underside of ocular assembly removed from binoculars. ZOOM BINOCULARS/59
to one another. The positions of the cam tubes must precisely match one another. You can see what would happen if you had one ocular set as shown in Fig. D8A and the other ocular set as shown in Fig. D8B. The image from one ocular-the one set to the position shown in Fig. D8A-would be larger than the other image.
EYELENS
DISASSEMBLY OF THE OCULARS You may be able to remove the ocular assembly together with the hinge pin in a rocker-arm arm design. With a focus-knob design, you can unscrew the ocular shaft from the focus knob. Both techniques retain the gear timing. But you may lose the timing if you remove the ocular assembly from the rear end of the hinge pin-depending on the design. In Fig. DI9, the coupling gear stays with the ocular assembly. In that case, you don't lose the gear timing. However, if the coupling gear is loose as in Fig. DU, you lose the timing between the two cam tubes.
FIG. 015 Eyelens with eyecup removed. SCREWHEAD
ON ZOOM TUBE
Unless you have to reach the rear porro prisms, you may not have to remove the complete ocular assembly. Let's say you just want to disassemble the fixed ocular to reach the optics. First remove the rubber eyecupwith the binoculars shown in Fig. DI2, the rubber eyecup screws onto the ocular. In most binoculars, you can simply lift off the rubber eyecup. You can now see the two spanner holes in the eyelens of the fixed ocular, Fig. D15. Since the eyelens is threaded, you know that there's a good chance it's adjustable. Here a setscrew locks the eyelens in its adjusted position. Loosen the setscrew at the outer circumference of the fixed ocular. You can then unscrew the eyelens. On reassembly, it's necessary to reset the eyelens to the 0diopter position.
FIG. 016 Fixed ocular with eyelens removed. NOTCH
With the eyelens removed, you can see the end of the cam tube, Fig. DI6. You've already seen that the slot in the cam tube fits over a screwhead on the zoom ring. So, as the zoom ring turns, the cam tube also turns. Lift out the cam tube, Fig. D17. As you've already seen, the zooming element and the compensating element remain inside the cam tube. You can now see the guide slot in the ocular tube, Fig. DI8 . The guide slot receives the screwheads on the zooming element and the compensating element. To replace the cam tube, line up the screwheads on the two lens cells, Fig. D17. If you turn the two lens cells
601Z00M BINOCULARS
FIG. 017 Cam tube removed, set to maximum power.
to the 15X position, the screwheads nearly line up with the cam-tube notch, Fig. D17.
SCREWHEAD
ON ZOOM TUBE
Pass both screwheads tlu'ough the guide slot, Fig. D18, as you seat the cam tube. Then turn the cam tube as necessary until its notch fits over the zoom-tube screwhead, Fig. D16 . Use the same procedure to remove and replace the carn tube in the fixed ocular. As yet you haven't disturbed any timing. But, as mentioned earlier, you may disturb timing if you remove the complete ocular assembly from the hinge pin. You should therefore make some timing notes before disassembly-notes you can use for reassembly reference. With some zoom binoculars, it's difficult to install the ocular assembly unless you first remove the cam tubes. You may not be able to see the cam slots or the follower screws if you're trying to install the ocular assembly as a unit. However, with the cam tube removed from the fixed ocular, you can note the timing. First set the zoom lever to the maximum magnification-15X in this example. Then note the position of the zoom-tube screwhead with respect to the guide slot, Fig. D18. If you remove the ocular assembly, you now know the reassembly position for the left-hand zoom tube-the screwhead must be in the position shown in Fig. D18 with the zoom lever set to 15X. After you've replaced the ocular assembly-and fore you replace the fixed-ocular cam tube-set
bethe
GUIDE SLOT
FIG. 018 Fixed ocular with carn tube removed.
zoom lever to 15X. Then lift the fixed ocular slightly away from the binocular body-far enough to disengage the coupling gear from the zoom-tube gear. You can now turn the zoom tube to set its position as shown in Fig. D18. You can often remove and install the ocular assembly as a unit. Removing the ocular assembly together with the hinge pin-or unscrewing the ocular arm from the
ZOOMLEVER RING (MASTER)
FIG. 019 Ocular assembly removed with cam tubes. ZOOM BINOCULARS/61
FOCUS-LEVER
RING
o CAM SLOT FOR ZOOMING
ELEMENT CAM SLOT FOR COMPENSATING
ELEMENT
FIG. 020 Cam tube installed in ocular, set to lowest magnification.
focus knob--normally retains the ocular timing. In Fig. D19, we've removed the complete ocular assembly from the rear end of the hinge pin. In these binoculars, the coupling gear stays with the ocular assembly. No timing has then been lost. With the ocular assembly removed, Fig. D19, you can normally see the earn-tube slot for the compensating element. But you can only see the bottom end of the earn-tube slot for the zooming element, Fig. D20. Position the screwhead for the zooming element at the bottom of the earn slot. And position the screwhead for the compensating element at the top of its earn slot, Fig. D20. The zooming element and the compensating element are now in the lowest-magnification position. Now turn the zoom lever to the lowest-magnification position. Feed the screwheads into the guide slots as you seat the ocular assembly. Since the earn tubes were not removed, you should not have to adjust the magnification of either ocular. With the system shown in Fig. D18, there's only one way you can adjust the magnification of one ocular to match the other ocular-change the gear timing. Fig. D21 shows the earn tube from a similar geared system. But this system allows you to adjust the earn-tube position without changing gear timing. Each earn tube has six "fingers" on its top edge-three on each side, Fig. D21. The fingers fit over tabs at the tops of the zoom tubes, Fig. D22.
62/Z00M
BINOCULARS
SCREWHEAD ON ZOOMING ELEMENT
SCREWHEAD ON COMPENSATING ELEMENT
FIG. 021 Cam tube removed.
ZOOM TUBES
FIG. 022 Ocular end of binoculars with cam tubes removed.
Except for the coupling between the zoom tube and the earn tube, the design is very similar to the first zoom binoculars we described. The end of each zoom tube screws into the zoom-tube gear, Fig. D24. The zoomlever ring on one side also screws onto the end of the master zoom tube. On the other side, a retaining ring screws onto the end of the slave zoom tube. As you turn the zoom lever, the zoom-lever ring turns the master zoom tube. The master zoom-tube gear connects to the slave zoom-tube gear through the gear train, Fig. D26. Both zoom tubes then turn as you move the focus lever. The zoom tubes rotate the earn tubes. The screwheads on the movable lens groups, Fig. D23, pass into fixed guide slots in the ocular sleeves, Fig. D22. So, as the zoom tube turns, the lens groups move in or out along the earn slots. Note again that the earn slots run in opposite directions, Fig. D23-as the zooming element moves to the back of the earn tube, the compensating element moves to the front of the earn tube.
to the front of the ocular (less magnification). For example, suppose that the earn tube is seated as shown in Fig. D25. If you lift and turn the earn tube in one direction, the zooming element moves toward the front of the binoculars-lower magnification. If you lift and turn the earn tube in the opposite direction, the zooming element moves toward the back of the binoculars-higher magnification. As with other binocular repairs, it's best to remove only one earn tube at a time. You can then use the other side of the binoculars as your standard. Adjust the rotational position of the earn tube on one side until the magnifi-
SCREWHEADS
To reach the tops of the earn tubes, remove the rubber eyecups. Then unscrew the eyelenses. It's now possible to lift out the earn tubes-or to change the rotational positions to adjust the magnification. Change the rotational position by lifting a earn tube until its fingers clear the tabs on the zoom tube. Then rotate the earn tube in one direction or the other. As you rotate the earn tube, the movable lens cells change position-the zooming element, Fig. D2S, moves closer to the back of the ocular (more magnification) or closer
FIG. 023 Cam tube removed.
ZOOM BINOCULARS/63
cation matches the other side (your standard side). Later in this section, we'll describe some methods you can use to compare the magnification of the oculars.
ZOOM TUBE
If you're going to lift out the cam tube, you might first mark its adjusted position-marking the adjustment may save you a lot of time on reassembly. You can put dabs of white paint on the tabs of the zoom tube, Fig. D25, to mark the positions of the cam-tube fingers. Then, on reassembly, align the two screwheads, Fig. D23, with one another. Seat the cam tube, making sure the two screwheads pass through the guide slot, Fig. D22. Now turn the cam tube until its fingers align with your paint marks. Seat the carn tube and screw on the eyelens. In some repairs, it may be necessary to remove the complete ocular assembly. Perhaps you want to reach the ocular-side porro prisms for a collimation adjustment. You can remove the ocular assembly together with the carn tubes.
KNOB /CONTROL
I
I
J
=t"0CULAR ARM ZOOM-TUBE
GEAR
i
"
!
~~!~M~
I """"'''''~'''"''''''''"~ ZOOM LEVER
FIG. 024
As with other binoculars, remove the ocular assembly together with the hinge pin (rocker-arm design). Or unscrew the ocular shaft from the focus knob (focusknob design). In some designs, it may be necessary to remove the ocular arms from the rear end of the hinge pin. With the binoculars shown in Fig. D22, you can remove the ocular assembly from the rear end of the hinge pin by taking out the center screw. From the underside of the ocular assembly, you can see the gears, Fig. D26. The large zoom-tube gears that screw onto the bottoms of the zoom tubes aren't visible in Fig. D26--one fits on the other side of the zoomlever ring, and the other fits on the other side of the retaining ring, Fig. D26. Unlike the design shown earlier, the center coupling gear remains in place-removing the ocular assembly does not disturb gear timing.
CAM TUBE
FIG. 025 Ocular with eyelens removed.
RETAINING
FIG. 026 Underside of ocular assembly. 64JZOOMBINOCULARS
RING
FIG. 027 Binoculars with ocular assembly removed.
Since you can adjust the position of each carn tube, the gear timing may not seem so critical. However, if you disturb the gear timing, your timing marks will no longer be valid. Disturbing the gear timing will also throw off the index dot for the magnification-the index dot is on the retaining ring, Fig. D26. You can now remove the rear prism covers. Unscrew the ocular sleeves, Fig. D27. Remove the screws holding the prism covers. If the binoculars have a rubberlike covering, you may have to peel aside the rubber to reach the prism-cover screw(s).
FIG. 028 The metal strap for coupling the slave to the master.
OTHER COUPLING SYSTEMS Gear coupling is the most common method of connecting the two oculars. But there are other systems. All that's needed is a method of turning the slave zoom tube when you turn the master zoom tube. A cord or a flexible metal strap can also provide the coupling. Fig. D28 shows a typical metal strap, a piece of spring steel around 3mm wide and O.2mm thick. One end of the metal strap hooks to a slot in the zoomlever ring (master); the other end hooks to a slot in the retaining ring (slave). The design is similar to the geared systems we've already described. The zoom-lever ring and the retaining ring screw onto the lower ends of the zoom tubes. But rather than gears connecting the master zoom tube to the slave zoom tube, the metal strap provides the connection. The underside of each binocular arm has a channel for the metal strap, Fig. D29. When you assemble the two ocular arms, the channel runs between the two ocular openings, Fig. D30.
CHANNEL FOR METAL STRAP
FIG. 029
ZOOM BINOCULARS/65
The metal strap lies in the channel as shown in Fig. D31. Slots in the retaining ring and the zoom-lever ring fit over the bent ends of the metal strap. There's no timing in this system-the proper positioning of the slave zoom tube depends on the length of the metal strap. You can remove the ocular assembly as a unit. Or you can first remove the carn tubes. To remove the carn tubes, unscrew the eyelenses. Typically, plastic clips still hold the cam tubes in place-the plastic clips fit over the top ends of the earn tubes. Remove the plastic clips and lift out the carn tubes. Remove the complete ocular assembly with the hinge pin or by unscrewing the ocular shaft from the focus knob. If you want to remove the ocular arms from the ocular shaft, take off the IPO scale. There may be a retaining ring or a screw under the IPO scale that holds the ocular arms to the ocular shaft. But after removing the retaining ring, you'll probably find that you still can't lift off the ocular arms. It's necessary to first loosen a setscrew at the hinge of one ocular arm. The setscrew passes into the slot at the end of the ocular shaft, Fig. 033. You'll see the purpose of the setscrew and the ocular-shaft slot in a moment.
FIG. 030 METAL STRAP
FIG. 031 ZOOM-LEVER
RING RETAINING
RING
With the ocular assembly removed, you can unscrew the zoom tubes--one zoom tube screws into the zoomlever ring, and the other zoom tube screws into the retaining ring. You can now lift out the zoom-lever ring, the retaining ring, and the metal strap.
FIG. 032 On reassembly, lay the metal strap in the channel as shown in Fig. 031. Seat the retaining ring with its slot over one end of the metal strap. Seat the zoom-lever ring with its slot over the other end of the metal strap, Fig. D32. Then screw in the zoom tubes from the opposite ends of the ocular assembly. Turning the zoom-lever ring now moves one zoom ring-the zoom ring that screws into the zoom-lever ring. The metal strap moves the retaining ring in the sarne direction. And the retaining ling turns the other zoom tube-the zoom tube that screws into the retaining ring. The zoom tubes turn the two carn tubes.
FIG. 033 Binoculars with ocular assembly removed.
661Z00M BINOCULARS
You can now see the reason for the setscrew and the slot in the end of the ocular
CURVED WALL OF OCULAR-SHAFT
SLOT
FIG. 034
shaft, Fig. 033. When you replace the ocular arms, the centers of the ocular arms fit over the slot in the ocular shaft, Fig. 033. The wall inside the ocular-shaft slot has a curved surface to route the metal band. Fig. 034 shows the ocular shaft from the underside of the ocular arms-a view you can't actually see with the ocular arms in place. When you replace the setscrew, the curved wall of the ocular-shaft slot and the end of the setscrew form a channel for the metal strap--a channel that routes the center of the metal strap over the ocular shaft. The metal strap follows the curve of the ocular-shaft wall as you change the interpupillary distance by spreading the binocular sides.
REMOVING THE OCULAR TUBES As with other binoculars, you may have to unscrew the ocular tubes, Fig. 033, to take off the prism covers. But unscrewing the ocular tubes may be more difficult in zoom binoculars. You'll find that the ocular tubes in zoom binoculars are very tight. The ocular tubes in zoom binoculars have the guide slots. It's therefore critical that the ocular tubes don't work loose. Remember that the guide slots prevent the movable
elements from rotating. The movable elements then move in or out along the cam slots. But if an ocular tube works loose, it turns with the cam tube. The movable elements in that ocular then won't move in or out. And the magnification won't change. If you note that the magnification in one ocular changes as you move the zoom lever-but the magnification in the other ocular does not change, the ocular tube has probably worked loose. Yet, even though it takes quite a bit of torque to unscrew the ocular tube, you must be careful to avoid damage. If you distort the ocular tube, the zooming elements won't move freely. The zoom lever may then bind. Or the magnification change in one ocular won't match the magnification change in the other ocular. You won't normally distort the metal ocular tubes with your flexic1amp wrench. But zoom binoculars often use plastic ocular tubes. And it's very easy to damage a plastic ocular tube by squeezing the sides-even with a flexic1amp wrench. Clamp your flexiclamp on the base of the ocular tube (rather than on the top). And try to avoid squeezing together the sides of the ocular tube any more than necessary for a good grip.
ZOOM BINOCULARS/67
OTHER TYPES OF ZOOM BINOCULARS The zoom binoculars we've covered all use variablepower oculars-that's by far the most common type. But some high-end binoculars use a different systema system that employs zoom lenses inside the binocular bodies. BARREL
Fig. D35 shows a binocular style that uses roof-angle prisms and internal zoom lenses. The zoom lenses are in the barrels that fit inside the binocular tubes. Thrning the zoom control moves a threaded shaft that shifts the movable optics inside each barrel. As with the zoom oculars, a zooming group and a compensating group follow earn slots. The zooming group changes the size of the image. And the compensating group holds the focal point of the objective lens at the same position.
ZOOM KNOB
FOCUS KNOB
CHECKING OCULAR TIMING If you're in doubt about restoring the proper ocular timing, you may need way to compare image sizes. One method is to make yourself a target like the one shown in Fig. D36-a series of circles. It may take some experimentation in your own facility to determine the sizes of the circles-depending on how much room you can allow.
FIG. 035
You can then position the binoculars at a distance that allows one of the circles to fill the field of view. View through the ocular you haven't disassembled as you set the position of the binoculars. Now, without changing your target distance, view through the ocular you've repaired. Compare the image size-the number of circles you can see. As you change the zoom setting, make sure the two oculars cover the same field.
1 2
FIG. 036
681Z00M BINOCULARS
3 4
5 6
TANCE T E RS TANCE RS RIVER
PORRO PRISM VERNIER CALIPER SOFT-JAW PLiER SETSCREW ROTATIONAL ERROR RETICLE REAL IMAGE PRISM CLAMP TUBE ZOOM TERRESTRIAL TOTAL ZOOMING VARIFOCAL LENS INTERNAL ELEMENT LENS TELESCOPE REFLECTION SPANNER STRAP WRENCH WRENCH SCREWDRIVER ROOF-ANGLE PRISM ROCKER ARM RIGHT-ANGLE PRISM PRISM-ERECTING REFRACTION SYSTEM 6 SCREW, CROSSPOINT 9 18 30 12 5 27 1 2 11 57 1 13, 16 55 4 20 19 16 56 2 13 10 1 15 32 7 21 26 53 9 8 8,55 23,42 5,25 12,30,46 4,22 4,11 4,27 4,25 4,26 22,37,48 37,38,41 15,38,54 34,45 7,27 4,24,31 22,47 11, TELESCOPE ZOOM BINOCULARS
INDEX
69
ALII SERVICE NOTES P.o. BOX 30871 Honolulu, HI 96820
