J. Gregory McHone, Grand Manan, Canada
During several years of geological studies, my Olympus BH-2 BHSP petrographic microscope (above) has served very well with an excellent trinocular TR30 head. It is equipped with a pair of WHK 10x eyepieces, one of which has a pol-type crosshair reticle (or reticule or graticule) with a helical screw for focusing, while the other is a non-reticle type for the left eye tube, which has a diopter focus. These provide a good wide field number of 20, or about 2 mm of view with the 10X objective if there is no other magnification. Through time I have acquired another 10x with a Walton-Becket reticle for measuring fibers, a pair of WHK 8x, and a pair of WHK 15x power eyepieces, which are sometimes useful for detailed studies (mostly they just make me feel more empowered, my wife would say).
Many of my rock sections are somewhat coarse, with grain sizes of several tenths mm or more. To interpret crystallization histories from their textures, it is helpful to see a lot of the thin section slides at once. Recently, I got a deal on an Olympus super-wide-field trinocular SWTR head, which don't come along every day, and they are pretty darn expensive when you find one. This one was priced down because of a stiff eye width adjustment and a surface blemish, but with lubrication and a mix of paint to match "olympus putty," those faults became negligible.
Already in my "someday" parts collection was a pair of super wide field Olympus SWHK 10X L oculars, which have 30 mm insertion tubes to match this SWTR head model (the TR30 has the older standard 23.2 mm tubes). The larger eyepieces have a very wide field number of 26.5, about as big as on a Leitz Orthoplan I used and admired in past years. A special condenser would be needed to illuminate the greater area of a very low power objective such as the SPlan 2x, but my flip-up pol condenser works OK with the 4x and higher DPlan objective powers, even at this high field number. Olympus did not design the DPlans to have a flat focus across more than about FN21; instead, the SPlan objective line is recommended for a completely flat field with the super-wide optics. Even so, there is not much to complain about with my DPlan PO objectives at FN26.5. I was also happy to find that my various WHK eyepieces work quite well with the new head, when fitted with adapters for the 30 mm eyepiece tubes, although of course they still have their FN20 field view. The SWTR head does not have diopter tube focusing for the eyepieces, so it is helpful for both eyepieces to have their own helical focus.
My Objectives for the Oculars (sorry, bad pun)
Although they looked nice on the outside, both of the SWHK eyepieces had problems. First of all, they each had a photo reticle, while of course I need one with a cross hair and the other without a reticle. They were a little dirty, and cleaning the exterior glass did not resolve that to my satisfaction. Also, they were both frozen solid, that is, the helical screw for adjusting the top lens to bring the reticle into focus would not budge. Trying to force it by hand got me nothing except concern that I might damage these expensive hard-to-find eyepieces. I have heard of others with this problem, due to grease that hardened with time. Maybe a little unexpected, given that they were probably "new" in the 1980s, which seems pretty recent to me! So, taking them apart for refurbishing became my project.
My goals for this article are to illustrate the disassembly and cleaning of this very fine
Olympuseyepiece, and to provide a clue to replacing its reticle. I can imagine some professional microscope technicians are starting to scowl at me already, so let me say right up front, you really should send such pieces off to a pro shop for this work. Actually, it would have saved me some minor grief to do that, but too late now. The reticle was a harder problem than I expected, but the disassembly and cleaning was reasonably straight-forward and could be done by most people who have some proper tools, and a bit of patience. Microscope parts from a high-quality maker like Olympus are a pleasure to work on, not just because of good materials with good fit and finish, but because they can actually be taken apart and put back together again. Some of the cheap or unknown brands have their pieces stuck together so they cannot be serviced, only tossed out. Boy, does that go against my scotch-irish upbringing (OK, I can be cheap too).
Anyway, I am not a trained service technician, only a geologist who studies rocks, and also a hobbyist who likes to fix up microscopes. For myself, not for other people. Some of my scopes are for use in my lab, some sit on my shelf to admire or for future activity, and some I sell on eBay after they look good and work well. A few end up in a parts box under the bench.
Taking apart an eyepiece is not a job for the average tools you might have for common trades and tasks. Ian Walker's article on refurbishing a LOMO microscope in Micscape (July 2004 issue) included his recommendation for synthetic lubricants by Nye, and a small bit tool set by Wiha. I obtained these on the internet from MicroTools, Inc. but the same kits are no doubt available elsewhere. They are of excellent quality, I use them often, and you will need something similar. You should also have a spanner (a small adjustable wrench for turning screw rings), needle nose pliers, and other common accessories. My rubber grip wrench proved to be quite valuable. Maybe you also need some talent or dexterity with taking apart small pieces, although I am rather clumsy with my large hands. When small parts fall where I can't see them (not a rare occurrence), I never wait to look for them later but immediately search until they are found, no matter how long it takes. But when the work become frustrating, I have learned to walk away for a while and come back to it again later.
For cleaning, my current lens cleaner is a commercial isopropanol (alcohol) solution in a bottle, as well as lens papers already saturated with an alcohol solution ("Zeiss Lens Cloths"), along with a soft cotton cloth, paper towels, etc. And pure cotton swabs -- a lot of them. My solvent collection includes 8 or 10 various chemicals, most of which are volatile, toxic, and stink like heck. One of the worst is acetone, which I try to avoid. For most of them you need good ventilation, and to stay away from flames and sparks! For this project I used "Goof Off," which contains xylene and some other volatile chemicals. It smells bad enough to drive away family members, which is possibly OK if you need to concentrate. Don't let children breath these fumes, or adults that you care about.
Obviously, you need some bench space with a light colored table cloth, and good lighting.
As I mentioned, the eyepieces looked pretty good. But this one had a small tilt to the top section (you might notice it below), which could be related to some earlier effort gone wrong to fix the frozen helical adjustment. The little boxed P denotes the presence of a photo reticle, which has concentric rectangles used to help compose areas of the view for different film sizes. I don't use film much any more, and when I do there is a photo eyepiece in a camera tube accessory that allows precise focusing and composition. For my intended use of this eyepiece, it is only in the way and I wanted it out. We geologists need a cross hair reticle instead, mainly to characterize the extinction angles of minerals.
The fact that the eyepiece has a permanent label for the reticle in it must mean that Olympus intends it to be dedicated to that particular use. I suppose there is another version available with a little plus symbol in a circle, showing the presence of the crosshair that I need. Maybe a more affluent lab has a box full of various ocular versions, and you just pull out the ones you want for the work to be done. Good for Olympus' bottom line, but not good for my budget. I already had this pair, I did not need any with a photo reticle, and I believed I could restore and modify them on my own. Heck, I'm not cheap, just thrifty!
The first step was to pull off the plastic eye guard, which is flexible but somewhat stuck to the upper tube section. It needs to be stuck, because you must turn the inner helical focusing section with it. But it came right off, and three small set screws were now exposed around the rim.
When each of these three was backed out (but not removed), the top eye rim became detached from the interior helical section. It is a separate and empty barrel that is screwed to the middle tube section with a threaded base. Backing out the set screws released the top from the stuck interior helical screw section, allowing the top to be unscrewed and removed. I discovered that this piece had been pulled up and out of the set screw slot on one side, which caused the top to be tilted. Luckily it did not appear to be damaged. Here are the three pieces I had so far:
The next task was to free up the frozen helical screw section. My hands could not get a good grip on it, but I have a set of Grip wrenches, which have a strong rubber band that can be adjusted to get a tight grip on round objects. Plus, it is less likely to cause damage to delicate parts. It worked right away, and probably for the first time in years, the interior lens tube was unscrewed and pulled out.
Here is what it looks like. Notice how the old grease has hardened to a green color. I've seen that on some Zeiss parts as well. Down in the main tube the top of the reticle is in view. The hard brass threads on the outside of the upper lens tube could easily strip the soft aluminum threads on the inside of the main tube, and even after cleaning and lubricating, they do not necessarily go back together easily (I had a bit of trouble). Don't force it.
In the tube below the reticle, there is another lens at the bottom. This is in a separate lower tube section, held tight with three more set screws around the outer main barrel. The large screw head is the pin for a slot in the eyepiece tube, which keeps the eyepiece stationary while you turn the helical focus. It also aligns the reticle pattern with the axis of the microscope view. Back out the three set screws but do not remove them.
The reason I say do not remove them is because the lower tube set screws are very, very small. If they fall out anywhere that you do not expect, they might be very hard to find again. I let one out just to see what they look like -- it is the flea below the end of the tube. Much too small for my fat fingers to hold for re-inserting it, or even to easily pick up. But if you put a tiny dab of heavy lube grease on the tip of the little Wiha screw bit, the set screw will stick to it and can be put back into its place.
With the set screws backed out, the bottom lens tube section unscrews and separates. In the center tube you can see the bottom of the photo reticle. There is a rim in the tube for the reticle to seat against, but it does not look like something that comes out to release the reticle.
Here are the pieces disassembled so far. Notice how they are carefully machined and nicely finished inside and out -- signs of true quality.
Looking into the main center tube from the top, the collar of the upper rim above the reticle shows two slots, which can only be for the pins of a spanner wrench. On other eyepieces such as some by Zeiss, the reticle collar is threaded and can be unscrewed using a spanner, releasing the reticle. I tried to do that here, but it would not budge. I soaked it in my Goof Off with no effect. Although I had expected to add it to my reticle collection, I decided that the photo reticle has very little value for my future needs, and with it in place my eyepiece is not very good, so I broke it out.
As I cleaned out reticle shards with a pointed awl, the collar suddenly popped free. It was not threaded at all, just stuck in place, and it held the reticle by wrapping tightly around it. I didn't get a picture of it, sorry. Apparently the slots in the upper collar exist so you can turn the reticle to properly align it with the tube pin and view axis. The collar did not seem to have merely a friction fit, so I assume that Olympus fixed it in place after any adjustment with some kind of cement. If so, it might be released by a solvent other than xylene (acetone comes to mind -- I hate acetone).
By chance I happened to have a 26 mm diameter cross hair reticle in my parts collection, which was just about 1 mm too wide for the reticle collar. The rest of my collection is for smaller eyepieces. Although probably one in the exact size could be found to purchase somewhere, I decided to try to modify mine to make it fit. And after about a half hour of careful grinding of the reticle edges with a diamond surfaced file, it finally did fit OK, and I used a few small dabs of rubber cement to fix the reticle into the collar. After it set up I put a few more dabs onto the collar and put it back into the tube. By sighting down the outer and inner edges of the tube, the cross hair could be aligned with the tube pin using my spanner while the cement was still soft. If it is ever necessary in the future, rubber cement can be released with the solvents I have, so I will not be breaking out this reticle! After it hardened, I cleaned all the glass surfaces. They have to be spotless, so it took some time and many alcohol wipes.
After everything was dry, I screwed the lower lens tube back on and tightened the tiny set screws.
Also while parts were drying, the old hardened grease was removed with the Goof Off solvent on some cotton swabs.
The helical threads were then lubricated with a fairly stiff viscosity Nyogel grease. But how easily they turn is an individual preference, and you can control this to some degree by the grease you choose. My understanding is that synthetic grease will not dry out and harden with time.
As mentioned above, it was not easy to get this upper lens tube to screw back into the center helical thread. I finally scraped out and sharpened the starting edges of the thread slots with a push pin, and with some more lubricant, it connected properly and right away was silky smooth to turn. Life is good!
The top eye cap tube was then screwed back onto the outer barrel threads (the black ones in the photo below the brass helical screw). If the helical screw is down as far as it will go, the 8 mark should be close to the white mark below it. The top cap needs to be held down tightly as the three set screws are tightened, to be sure that the screws go into their rim slot.
Next, the soft outer plastic eye guard needed to be snapped back into place. I put a few more dabs of rubber cement into its inner rim to fix the guard to the top lens tube, as it must turn the lens to focus on the reticle without slipping. A final exterior cleaning and the job was done. Total work time was about 2 hours, but a lot of this was for learning rather than doing.
Soon afterward, the other eyepiece was taken apart and cleaned exactly like this one, except I left the reticle slot empty. Here they are back in the SWTR head, ready for work. The right one has the cross hair reticle, the left one is without a reticle, but this positioning is by choice and not required by the eyepiece tubes.
The helical screw focusing is now smooth and precise, just as it should be. Even after a lot of care in cleaning, there is still a tiny speck or two visible on the reticle. I try to ignore it but eventually will need to take the eyepiece apart again for better cleaning. This head and eyepieces are a real delight to use, and the view is like flying over my rock section surface in a small airplane. Awesome, and yes, empowering!
Feel free to contact me, Greg McHone, with questions or comments (even criticisms if they have future value).
Grand Manan (the Bermuda of Canada), New Brunswick
Published in the August 2008 edition of Micscape.
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