Olympus BH2 BHSP with reflected light

[microcosmos]

I decided to get an Olympus BHSP after encountering serious opto-mechanical problems with my Radical RPL-3T polarizing microscope and after reading Greg McHone's article on his BHSP. The trouble with the Radical instrument was that it wasn't a good instrument in bad condition but the other way round. The former case could be fixed by cleaning or repairing the parts but I thought the latter case was best fixed by getting another microscope!

I was lucky to find a working and mostly complete BHSP on eBay, which meant I could start using it immediately on delivery. However, I wanted to replace some parts to make it the best instrument it could be for my work in polarizing and petrographic microscopy.

I decided to sacrifice dark field, phase contrast and DIC as the required components would add much expense and they cannot be installed on the microscope at the same time as the BHSP components that are specially designed for quantitative petrography.

The nosepiece holds only four objectives because of the space taken up by the centering mechanisms for the individual objectives. I do like the silver-coloured metal knurling of the nosepiece (compared with the black colour of the regular BH2 nosepiece).

The following picture shows the current state of the instrument.



I am still putting together the vertical illuminator (part of which can be seen just above the nosepiece) and will post more about that later.

Here are some of the bigger changes I have made to the standard BHSP so far:

- added the EOS-1D X camera (which I also use for normal photography) via a well-made third-party anodized aluminium tube (with NFK 2.5x photo eyepiece inside) that goes direct from the 38 mm dovetail to Nikon F mount, with Novoflex adapter to fit the Canon mount. I have Nikon F-mount bodies as well, therefore the choice of Nikon F-mount on the tube.

- changed the regular head to superwide head with superwide eyepieces. Here's a side-by-side comparison:



- added the A-FMP/AH-FMP mechanical stage.



- changed the Olympus D Ach PO objectives that came with the microscope to Nikon CF N plan apo 20/0.75, Zeiss Pol Z 2.5x and 10x, and an MSPlan 50x (shown above). The Nikon and Zeiss objectives look gorgeous on the BHSP. However these are only temporary (mostly) finite objectives from my existing inventory that I use without the vertical illuminator (which changes the scope from finite 160 mm to infinity). I will post about new objectives later.

The 100W lamp really helps when I use crossed polarizers with low-transparency samples at high magnification, or even normal brightfield with thick samples. With a 50W or 20W lamp they are very dim as I found on my Radical instrument.

- of course, the microscope came without the centering wrenches so I have been making them out of short screwdrivers with hard plastic tubing:



It spends the night in an upturned box with dessicants inside. I was lucky to have a box of the perfect dimensions. I have since lined the box with plastic sheeting to make it more airtight.

[carlh6902]

The Nikon CF objectives and the Olympus SWHK eyepieces are a poor match.

Carl

[microcosmos]

Yes it’s not ideal but I discovered the Nikon actually gives better images with the SWHK than the D Ach PO I currently have, which are of course not ideal themselves for the SWHK. The Nikon still gives less aberration and higher resolution and is flat field all the way to FN26.5.

As mentioned the Nikon and Zeiss are only temporary objectives for the BHSP that I happen to have in my inventory, and I’m getting more suitable objectives which I’ll post about later.

But I must say I’ve enjoyed using the Nikon and Zeiss over the past few weeks - they may have some aberration but they do get along ok with the BHSP and SWHK and I’ve seen beautiful things and made some optical mineralogy measurements.

[microcosmos]

My screwdriver bits just arrived and I made the second centering wrench:



With the spare bits and lots of tubing which came from frozen fish packaging, I will never be short of centering wrenches again.

Now I can finally center the stage and objectives! One can use regular screwdrivers but they are usually too long for good control and fall off the microscope when you take your hands off them.

[microcosmos]

Last night I installed the crosshair-micrometer graticule necessary for centering and angle measurements in optical mineralogy. The SWHK needs a large 28 mm graticule - I had a hard time finding one that had the right pattern. Finally I got it made to special order by Shibuya in Japan. Apparently they're the ones who supply graticules to Olympus, as the case containing the graticule had "Olympus" engraved on it [see edit below].



As detailed in this thread, the eyepiece shown here is different from the photo-reticle SWHK in Greg McHone's article. My situation was slightly trickier as I had to disassemble the eyepiece from the top and glue the graticule onto the aperture shelf with E6000, as there was no detachable graticule holder at the bottom of the eyepiece.

The crosshairs have to be in the NSEW orientation when the orientation screw on the side of the eyepiece is sitting in the slot in the head tube. I manually adjusted the orientation of the graticule by gently pressing down on it with a microfibre lens cloth and coaxing it to rotate. It doesn't have to be super precise because on the BHSP you can rotate both the polarizer and analyzer and zero their scales (at extinction) exactly to the crosshairs.

When applying the cement you have to be very careful not to cause the graticule to rotate as you dab the cement onto the side, otherwise you have to use acetone to remove the cement and start all over again.

[edit: a distributor just told me that Olympus makes their own graticules, so I'm not sure why my Shibuya graticules came in Olympus-labelled cases.]

[microcosmos]

I have been testing a pair of loaned SWH 10x eyepieces. They're the BX-series successor to the SWHK. I didn't realize how much larger the SWH was. When I first saw it physically, I thought I was looking at a condenser or something!



They give the same field of view on the BH2 head as the SWHK, but have a higher and more comfortable eyepoint. They also have slightly different compensation (or lack of) that work better with the current objectives than the SWHK. I was testing a couple of UPLFLN-P semi-apochromats - the SWH gives an aberration-free image but the SWHK gives a tiny bit of purple-green separation.

But the rotation of the SWH can't be locked on the BH2 head because the pin is in a different place. It can be fixed with some DIY workaround.

[microcosmos]

As mentioned the Nikon and Zeiss are only temporary objectives for the BHSP that I happen to have in my inventory, and I’m getting more suitable objectives which I’ll post about later.

Here they are - Olympus' UPLFLN-P 4x, 10x and 40x from their UIS2 system. I chose them because they are Olympus' best strain-free objectives, which are fortunately not their top-end objectives. They loaned me a set for testing before deciding. These objectives are also good at DIC, darkfield, UV and fluorescence, in case I want to do those in the future.



What drives me crazy is the cluttered Microsoft Word-processed Arial (or related) font digitally printed all over the objectives. Gone are the days of engraved technical lettering. I solved the problem by taping them up with gaffer tape, which has a nice matt black texture. This gives them the black barrels customary for pol objectives, and also makes them look like commandos.



With the SWHK eyepieces, the UPLFLN-P 4x has slightly less CA than the MSPlan 5x. The UPLFLN-P 10x has slightly more CA than the MSPlan 10x, but is slightly better in overall colour balance of out-of-focus areas and is more strain-free. The UPLFLN-P 40x gives a smooth and crisp image without almost no CA and I'm quite happy with it.

The fourth objective on the turret is the good old MSPlan 50x which I found to be very satisfactory for my no-coverslip needs.

[PeteM]

As Carl noted above, while you have some first-class optics - the mix you're using is not optimal.

The Olympus finite optics, regardless of whether you use a regular trinocular or a superwide, want the corresponding "K" eyepieces (WHK, SWHK). "Chrome free" finite Nikon objectives aren't a good match, though the effects would likely be most visible taking photos.

The newer UIS infinite optics you're trying aren't meant to be used with either of the Olympus BHS heads or the "K" eyepieces. Instead, you'd want to adapt a BX head with a proper matching tube lens and the corresponding eyepieces. A BHS is (mechanically and illumination-wise) a fine stand to adapt to BX optics, but you want the objectives - tube lens - eyepieces to be the proper infinite set.

[microcosmos]

Thanks for your comments. I did consider the factors you mentioned, and other factors peculiar to my needs, before settling on this. I think it is the most optimal configuration that does what I want it to do and gives me a microscope that I enjoy using. Let me break it down a bit.

- I want the microscope to be a BHSP and not a BX-P or any other model, for build and design reasons.
- Strain-free optics is a priority. After that, aberration correction and flat field should be as high as possible.
- I want reflected light on the same instrument, so that makes it an infinity instrument.

The above considerations resulted in my frankenscope if you like.

As Carl noted above, while you have some first-class optics - the mix you're using is not optimal.

I understand that the first-class optics are not performing at their designed first-class level, but after testing it out (see my previous post), they still give me better results than using lower-end optics. I am quite happy with that.

The Olympus finite optics, regardless of whether you use a regular trinocular or a superwide, want the corresponding "K" eyepieces (WHK, SWHK). "Chrome free" finite Nikon objectives aren't a good match, though the effects would likely be most visible taking photos.

The finite optics were just a temporary stand-in and have since been retired, so this is no longer an issue. The Nikon CF N 20/0.75 plan apo used to be on my Radical instrument with Nikon eyepieces. I just wanted to enjoy it a bit more on the BHSP while I could. It still gave very good images even with the wrong compensation of the SWHK.

As for photomicrography, I am modifying my dovetail to take PE projection eyepieces (as discussed in this thread), so that should optimise the quality. I'm not too picky about having completely no CA at all. If the image is reasonably good without cropping and can illustrate the scientific result accurately, I am happy.

The newer UIS infinite optics you're trying aren't meant to be used with either of the Olympus BHS heads or the "K" eyepieces.

I know I'm doing many "illegal" things - including stacking the intermediate polarizing attachment on top of the vertical illuminator, which hasn't been mentioned, which has given me some minor problems with the field of view of high-powered objectives and probably affects optical quality slightly.

I considered changing to the SWH eyepieces, a pair of which Olympus loaned to me for testing (see earlier post). Of course, with the UIS objectives they give slightly less CA than the SWHK. But it is very difficult to get the cross-scale eyepiece graticule into it, and the alignment screw is also at the wrong place so I can slot the screw into the groove on the BH2 head to stop it from rotating (I need the crosshairs to be fixed in the NSEW orientation).

I also considered changing to the U-POC condenser, which fits on the BHSP. The BH2-POC is an Abbe, while the U-POC is achromatic aplanatic and probably a better match for UIS. But I'm worried that the build quality may not be as good as the BH2-POC. I'll also be wasting the nice BH2-POC since it will be very difficult to find a new owner.

Instead, you'd want to adapt a BX head with a proper matching tube lens and the corresponding eyepieces. A BHS is (mechanically and illumination-wise) a fine stand to adapt to BX optics, but you want the objectives - tube lens - eyepieces to be the proper infinite set.

But I love the BH2 trinocular head with its pentagonal asymmetric cross-section - it's like a Lotus supercar. The BX head looks ugly and plastic (although it might not actually be plastic) and I cannot imagine putting it on my microscope. I know it doesn't matter to many people, but to me a microscope must both function well and look good. It gives me great pleasure to look at a beautiful microscope, a visual manifestation of the wonder of engineering.

Another point I wish to add is that the optical quality is just one half of what I want from the microscope. The other important half to me of a microscope's quality is the alignment and calibration - the stage and objective centering to the crosshairs, the calibration of the eyepiece micrometer, the calibration of the crossed polarizer extinction angle to the crosshairs, the calibration of the fine focus knob graduations. My current setup doesn't compromise any of this - I can do still all of it to great accuracy.

[microcosmos]

Another point I wish to add is that the optical quality is just one half of what I want from the microscope. The other important half to me of a microscope's quality is the alignment and calibration - the stage and objective centering to the crosshairs, the calibration of the eyepiece micrometer, the calibration of the crossed polarizer extinction angle to the crosshairs, the calibration of the fine focus knob graduations. My current setup doesn't compromise any of this - I can do still all of it to great accuracy.

Here's the orientation plate for aligning the crossed polarizers and crosshairs in the precise compass directions. It's not easy to find as distributors are unfamiliar with it and you have to give them the "top-secret launch code", U-PJ (which I spotted in the BX53-P manual) to enable them to call up the part in the system.

I found the instructions provided by Olympus for the use of the orientation plate incomplete and oversimplified, so I wrote up a full step-by-step guide for anyone who may need it - https://www.linyangchen.com/Petrographic-microscope-polarizer-orientation-plate

[microcosmos]

I am still putting together the vertical illuminator (part of which can be seen just above the nosepiece) and will post more about that later.

I finally put together a fully working vertical illuminator after several dead ends (lost packages, cancelled orders, defective parts, wrong sized components etc.).



The TGH transformer is a monster - I didn't realise it was so big and heavy (there's some perspective exaggeration in the photo but it is still very big).



I decided to go for a BH2-MA rather than the BH2-RLA. The MA has both aperture and field diaphragms for finessed control of light, and has a swing-out half-mirror to enjoy my transmitted light at full blast. The RLA has only one diaphragm, the mirror can't flip out of the way and it has features I don't need, like the auto ND filter and the darkfield setting.

I also decided on the MA over the UMA, as I preferred the MA's sleek and black "particle accelerator" look that complemented the rest of the BHSP's architecture and colour scheme.

Interestingly, the MA that I found is a "Mark II" - it is labeled "BH2-MA-2" and has a taller tube lens section with two lens elements/groups instead of one. I can't find any documentation of this "-2" variant. If anyone knows anything I'll be grateful for more information. One consequence of this extra tube lens height, plus the unauthorized stacking of the intermediate polarizing attachment on top of it, is that this is probably the tallest Olympus BH2-series microscope in the world.



The black oxide stainless steel dovetail on the trinocular head is the specially modified CNC version that takes a PE projection eyepiece as discussed in this thread. As discussed earlier, there are optical issues with the system although it is the best and a satisfactory tradeoff I have been able to find for my needs.

It's on to actual microscopy for now!

[microcosmos]

View from the front.



I gave it several nicknames in the course of retrofitting it - "Large Photon Collider", "Burj Olympus" etc.

[microcosmos]

Finally, some images from the microscope after optimizing the setup as far as I could (including ditching the PE eyepiece and going back to NFK).

Here's one using a Ricoh GRII compact camera handheld over one of the SWHK eyepieces, straight from the camera with no post-processing except adding the scale annotation (I may have adjusted the exposure a bit, but no saturation/sharpening/contrast etc.):



(crossed polars of a petrographic thin section of a norite/gabbro-type rock)

No aberrations are visible (even in the plane-polarized image not shown) unless you zoom in to 100% and even then they are not serious.

Here's a couple (plane polarized and crossed polarized) using the DSLR "observation platform" at the top of the skyscraper, again with no post-processing:




(pleochroic, high-relief, high-birefringence mineral with straight extinction, possibly epidote)

The aberrations are as expected from earlier testing of loaned objectives before deciding on the final configuration of the microscope. They certainly can't compare with the 100% aberration-free apochromatic VC images I had during my previous research with a fully optimized Nikon Ni-E, but I think it's a fair tradeoff in a home microscope that I configured with the aim of getting an all-round ultimate microscopy experience that's not just about getting aberration-free images.

The images above are somewhat not sharp, especially if you are using a Mac retina screen, as they are displayed at non-retina pixel resolution. The full set of retina-resolution images can be seen at https://www.linyangchen.com/Geology-Singapore-petrographic-thin-section.

[microcosmos]

I've just completed my latest photomicrography project - the first one using this BHSP.

It's a collection of polarized light images of thin sections of rocks from Singapore, along with petrographical analysis. The full collection can be viewed at https://www.linyangchen.com/Geology-Singapore-petrographic-thin-section

Photomicrographs of Singapore rocks are extremely rare, the only ones in existence (that I know of) being monochrome low-resolution reproductions in a 2009 publication on the geology of Singapore. This is the first and only (to my knowledge) collection of publicly available high-resolution full-colour images.

Here's a sample:



Enjoy!

[perrywespa]

I've been following this topic since you started and I think your efforts have paid off. Well done! I also noticed on your web site, the section of the Gandom Beryan meteorite looks like my home state of Georgia, USA!

[microcosmos]

The shape of the meteorite section did strike me as somehow familiar but I had no idea it was Georgia!

Thank you for your encouragement. I've had a good adventure so far and hope people will enjoy the pictures.

It's not done yet. I just realized to my horror, when testing the reflected light on an actual sample, that the vertical illuminator is full of glare, haze and fog.

After some investigation I think it's the dirty collector/field lenses (which were hard to reach for cleaning) plus the reflective finish on the inside of the tube (I have no idea why it came like that other than to make me do more work).

I was hoping to get away with not doing anything about it but it doesn't work. I'll have to disassemble the whole thing, completely this time, and do a thorough cleaning and flocking.

[smollerthings]

Striking pictures.

I'll have to disassemble the whole thing, completely this time, and do a thorough cleaning and flocking.

Please do take pictures of that too!

[microcosmos]

Striking pictures.

I'll have to disassemble the whole thing, completely this time, and do a thorough cleaning and flocking.

Please do take pictures of that too!

Ok, I will certainly take pictures as I (hope I) won't be opening it up again any time soon! The trouble is not just with the vertical illuminator itself but having to redo a few other calibrations to other parts of the microscope after I reassemble it - I need to re-orient the polarizers, re-center the stage and each of the objectives and re-calilbrate the eyepiece micrometer (although this last one has proven to be quite stable to disassembly).

[microcosmos]

I did it yesterday after the flocking tape arrived.



Here are some close-ups of the disassembled components of the BH2-MA-2 vertical illuminator:


The swing-out half mirror. There was already a patch of flocking (by Olympus I believe) directly opposite the mirror from the outlet of the light, but the photo shows the process of more flocking being added around the circumference.


The three sections of the horizontal tube. The middle section houses the field and aperture diaphragms; I did not dissassemble it further (there are screws and snake-eye drives you can unscrew) as it did not appear to need any cleaning. Photo shows them in cleaned state. Previously with lots of grease and light-coloured dirt making the inner surfaces highly reflective, and stains on the lenses.


The diaphragm adjustment rings.


Adding flocking and cutting to shape.


Leveling the filter slots when reconnecting the dovetails.

I didn't flock it 100% as some of the surfaces were difficult to stick the tape securely on. I am a bit lazy and just wanted a relatively quick and easy fix so I didn't go into painting and other methods. When the flocking tape arrived I realised it was more felty than I expected so I blew off the excess fibres as much as possible and hope it wouldn't shed too much into the microscope over time.

The image quality seems to have improved appreciably - the 4x went from unusable to usable, the 10x went from usable to good, and I haven't tested the 50x MSPlan but expect it to be better than before (it was good already).

Microscope re-oriented, re-centered, re-calibrated and fully operational.

[eKretz2]

I would love to see some before/after images if you have any. I'm thinking about trying to re-do the black parts of a few of my epi lenses and other bits in the light path. My brightfield images are looking a bit washed out.

[PeteM]

I might be wrong, but I believe microcosmos is using strain-free UIS Olympus objectives designed for transmitted light (and also reflected UV). If so, these may not be ideally designed for back illumination in the visible spectrum? I've had pretty good experience using Olympus metallurgical objectives in reflected mode, and sometimes a loss of contrast in trying to use regular objectives. My assumption has been that objectives designed primarily for transmitted light haven't necessarily been designed with the stops and anti-reflecton measures meant to handle back illumination. Could be that the UIS objectives, since they do get back illumination for fluorescence, might be OK -- but maybe not as well as objectives meant for that purpose in the visual spectrum??

In addition, there is a slight mismatch of infinity tube lenses between the older Olympus "f=180" epi units meant to have a finite head above them and the newer UIS objectives, tube lenses, heads, eyepieces, and photo relay optics.

The flocking of tubes surely looks to be an improvement, but further improvements might be possible.

[microcosmos]

Thank you all for your inputs. Unfortunately I don't have before/after images of the same object at the same magnification that can be directly compared, but I do have separate images from before and after at this link. The images are larger than the size displayed, so you can use ctrl+ or cmd+ to enlarge them on your screen and see more detail (or lack of).

The images with the 0.5mm scalebar were taken with the 4x UPLFLN-P UIS2 strain-free (before). Those with the 0.1mm scalebar were 10x UPLFLN-P UIS2 strain-free (before). The one with the 25 micrometer scalebar was 50x MSPlan (after). For the 50x I had to focus-stack a few images because the surface of the sample wasn't totally flat and horizontal or maybe because there's a slight misalignment in the optics. I'm afraid these images aren't really useful for before/after comparison.

The images have no sharpening, contrast or saturation added (all set to 0 in camera).

As Pete mentioned, the UIS objectives I am using were not designed for reflected light, at least in the visible spectrum. I'm glad they give me usable images nevertheless, which could partly be because I'm wowed by seeing reflected light on a polished thin section for the first time. There is a little bit more glare through the eyepiece when the epi field diaphgragm is opened to accommodate the full field of view, than when it is stopped down all the way (and blocking much of the field of view), but the glare isn't too bad (in all cases the aperture diaphragm was adjusted accordingly).

Previously I said the 4x was "unusable" before the modification, but I realise that I actually did take some usable images with it as shown on my webpage. But it looked bad through the eyepiece.

In fact it's the MSPlan 50x that doesn't seem to look so good, although it's usable. As discussed earlier I did some not-so-compatible stacking of components for various reasons, so I can't expect any of my objectives to perform at maximal quality although they do perform well given the circumstances.

I may have sounded a little too excited in my last post. There is some improvement after the flocking and cleaning, but not that much. I guess it boils down to whether the problem is deemed bad enough for one to interrupt any ongoing 'research' to take the microscope apart and do the maintenance.

What other improvements might be possible, short of changing the physical and optical components? I'm quite ok with it as it is but interested to explore more ideas.

[PeteM]

It could be that the MSPlan is more sensitive than the UIS objectives to having an analyzer stacked above the epi head?? The MSPlan was designed for the f=180 tube epi head -- and not normally with another intermediate piece stacked above it. On the other hand, infinity objectives are meant to allow some "infinity space." Maybe they are more tolerant of having both an epi head and an analyzer stacked together in this mixed-generations setup? It could also be mostly an issue of the higher magnification, compared to the 10x and 20x UIS objectives.

As you already know, carefully centering and closing down the field aperture a bit in an epi head is one way of getting better contrast.

It might also be interesting to try a full UIS-infinity-compatible conversion. I don't know much about the polarization analyzer, but I'd assume the tube lens in another f=180 epi head could be removed and then something like a U-TLA tube lens added in place of a trinocular head for direct imaging to a camera. Cost, at least on US ebay, would be around $200 for a spare epi head and a U-TLA tube lens. The glitch would be that costly analyzer. If it's a finite type, the matching lens would have to be (carefully) pulled out to give this a try. If simple polarization is all that's needed for the photos, a good extinction polarizer could probably be fitted under the U-TLA -- just removing the analyzer.

I thoroughly enjoy the work you're doing -- and the images keep getting better. Thank you for sharing them.

[microcosmos]

Thank you very much for the analysis. I read somewhere on the Olympus website for their current microscopes that they don't recommend using other makers' objectives as those objectives are not optimized for f = 180mm. This implies that the UIS objectives are optimized for 180 mm, although as you said their more modern design could still give more leeway than the MSPlan. But my 4x and 10x UIS are so far away in magnification from the 50x MSPlan that I suspect at least a fair proportion of the difference is due to the magnification difference.

I am not ready to do the UIS-compatible conversion but hopefully someone in a similar situation would find it a possible option. For one thing, this microscope has reached a point where optical optimization is giving diminishing returns for the accumulated expenditure, so my focus is shifting to "actual ops" if you like. I also love looking through eyepieces so removing the trinocular for direct camera imaging is not an option for me. I also want to preserve the full petrographic capabilities of the microscope for operational and sentimental reasons, so that means leaving the analyzer attachment untouched. It is the BH2 finite one and the matching lens is cemented in with a thick ring of cement (If I saw it correctly) so it would be suicidal for an inexperienced person like me to tamper with it!

The really annoying thing about that field diaphragm is that it lets me know it can give me amazing images, but only when it is stopped down so much that I can only see like 10-20% of the field of view. Actually now I realise the problem is probably made worse by the SWHK eyepieces because I have to open the field diaphragm almost fully to accommodate FN26.5. If I were using FN22 eyepieces, I would be able to stop down the diaphragm much more.

On a more technical note, the field diaphragm of the BH2-MA-2 doesn't seem to be centerable or at least easily centerable. When I disassembled it I saw two small inner screws holding the diaphragm, which I didn't touch. I'm not sure if they serve as centering screws, but even if they are, one can only reach them if the epi-illuminator is dismantled, so it is impossible to center the diaphragm while illuminated and looking through the microscope. In any case the diaphragm is just a very little bit off centre so it's not a problem for me.

I am glad you enjoyed some of my adventures. Alas I don't think the images will get much better in the near future but I'll see what I can do as I go along.

[microcosmos]

I just found another instance of the intermediate polarizing attachment stacked on top of the BH2-MA. I caught sight of it in a video "How is investigative analysis different from routing testing" by the McCrone Group. Here's a couple of screenshots:

Screenshot 2021-10-22 at 13.06.02.png (329.3 KiB) Viewed 6745 times

Screenshot 2021-10-22 at 13.16.24.png (391.4 KiB) Viewed 6744 times

They're using MDPlan objectives, which might be more tolerant than my FN26.5 objectives. At least it seems the stacked configuration can apparently be used for professional analysis. This is somewhat encouraging although it doesn't really matter to me. But it sure is nice to see McCrone using a similar configuration as it gives it some legitimacy!

I have also seen the polarizing attachment stacked on top of the BH2-UMA being used in a petrographic thin sectioning lab.

[microcosmos]

It might also be interesting to try a full UIS-infinity-compatible conversion. I don't know much about the polarization analyzer, but I'd assume the tube lens in another f=180 epi head could be removed and then something like a U-TLA tube lens added in place of a trinocular head for direct imaging to a camera. Cost, at least on US ebay, would be around $200 for a spare epi head and a U-TLA tube lens. The glitch would be that costly analyzer. If it's a finite type, the matching lens would have to be (carefully) pulled out to give this a try. If simple polarization is all that's needed for the photos, a good extinction polarizer could probably be fitted under the U-TLA -- just removing the analyzer.

The time has come. I'm now considering this full UIS-infinity-compatible conversion that Pete suggested, and it is actually not that difficult as long as the appropriate parts are CAD-designed and CNC machined.

This is the plan:

- remove the existing BH2-era tube lens from the MA2 epi-illuminator. This is simple - just unscrew the upper part of the epi-illuminator, which holds the tube lens, and ditch it.
- design and machine a connecting dovetail to connect the bottom of the analyzer assembly to the top of what remains of the epi-illuminator.
- remove the finite matching lens of the analyzer assembly. We thought this was going to be tricky but actually it's not - the mount holding the lens is actually just screwed onto the rest of the analyzer assembly, so all I have to do is to unscrew it! And machine a replacement mount without the lens, as the mount also contains the female dovetail connector needed to connect stuff above the analyzer.
- machine a dovetail mount to take the SWTLU tube lens, which is sold individually with a M41 threaded mount. Stack this tube lens assembly on top of the analyzer assembly.

And on top of the new tube lens goes the trinocular head, and it's done. The one thing I'm not yet sure of is whether the 151.3 mm focal length of the new tube lens matches distance to the eyepieces of the BH2 head.

I would be grateful for any advice.

[Scarodactyl]

Sounds like a plan!

The swtlu has the same 180mm fl as the bh2 era infinity tube lenses, so it's definitley possible to put a finite head above it and have everything spaced correctly.

If you end up with an extra bh2 era tube lens don't throw it out--I am sure some photomacrographers might pay for it to make a setup to use those bh2 objectives.

[microcosmos]

Although the Olympus tube lenses are all supposed to be "f = 180", I'm still confused. For example with this diagram of the SWTLU (numbers in mm):

Screenshot 2022-10-03 at 19.59.26.png (287.75 KiB) Viewed 3114 times

Where exactly is the "f = 180" in this diagram?

There's the number 151.3 mm from the reference plane to the focal plane. Does this mean that the distance from the tube lens to the back focal plane of the eyepieces should be 151.3 mm if I use the SWTLU? Will it work if I simply position the SWTLU right below the BH2 trinocular head? For now I'm assuming it will work well enough.

I actually have quite a diverse array of unused BH2 parts by now, but I could not find new homes for them. It's too difficult for me to sell internationally on ebay from my country, and I don't have any track record as a seller of microscope parts, and my shipping costs to the US and Europe, where most of the people who are interested in these things live, are too expensive even though I charge only just enough to cover my actual costs. So for now they just accumulate in my dry cabinets. Within the US and Europe there's more of an ecosystem for cycling these things.

[Scarodactyl]

You can get full specs for it on edmund.
The reference plane is just for convenience of mechanical measurements I suspect.

[microcosmos]

Thanks for the link. In any case I think I figured out where the 180 mm is. If you refer to the diagram above, I assume it's 33.6 + 151.3, minus the 4 mm overlap. So yes, I realise the "reference plane" is just for convenience.