"Improved" version of Olympus BH2 swing-out filter holder BH2-FH

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microcosmos
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"Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#1 Post by microcosmos » Sun Sep 12, 2021 10:51 am

Screenshot 2021-09-12 at 18.18.19.png
Screenshot 2021-09-12 at 18.18.19.png (287.22 KiB) Viewed 3899 times

I've tried unsuccessfully to find this filter holder for my microscope. Perhaps it's a blessing in disguise, as I don't actually like the design very much. It is too tall and bulky (I don't need three filter trays for my purposes) and the bottom circular bracket partially covers the nice engraved field diaphragm symbols on the field lens housing.

So I thought it might be worth designing and fabricating a customized version, taking the opportunity to throw in some improvements in functionality and ergonomics. Here's the progress so far:

Image

The bottom bracket incorporates these enhancements:

- thinner wall which doesn't cover the engraved field diaphragm scale and symbols on the field lens housing.

- hinge positioned at bearing 30 degrees (the above image doesn't show it in the correct orientation) instead of the ~60 degrees on the original Olympus part. This makes it easier to push the filters out into the space behind the light source, where they won't obstruct the hands.

- an additional curved flap (upper right in the image) acting as a filter stop to align the filters properly when swung in.

Image

The filter tray. The hinge is just a hole that slots into the pin on the bottom bracket. Olympus uses a retaining screw and tightening bolts which I feel are too complicated. There is no need for a screw to keep the trays down since there's gravity, and if the machining is accurate enough, the trays will swing properly without having to be fitted with tightness adjustment clamps.

The finished part will have two trays (making it less bulky than the Olympus part) for two ND filters of different densities. With them in various combinations, I'll have four different light intensity settings without having to reduce the voltage of the 100W bulb, which will upset the tungsten-halogen cycle and degrade the spectral characteristics as well as shorten its life I think. (My blue daylight filter has its own holder near the lamphouse at the back.)

Comments and suggestions are welcome. I've yet to address any potential design-for-manufacturability issues, but hopefully there won't be much of a problem.

deBult
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#2 Post by deBult » Sun Sep 12, 2021 1:48 pm

Would be interested in 2 sets please.

microcosmos
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#3 Post by microcosmos » Tue Sep 14, 2021 1:29 am

I am considering making the 3D files open source so people can download them and either 3D-print or machine it themselves or at their local suppliers, for personal non-commercial use. This will be cheaper and more environmentally friendly than me doing it and shipping them long distances.

But before I get to that I am having one set machined and need to put it through "sea trials"/"test flights" to check if it actually fits and works well.

The cost of machining is quite high for small quantities so 3D printing is more cost-effective. I decided to machine mine, out of personal preference and because I felt it was worth it since it is my own design.

I will update on progress.

MicroMan2
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#4 Post by MicroMan2 » Fri Sep 24, 2021 2:19 pm

Do you have experience testing these filter holders on the bottoms of the BH2 NIC/Phase Contrast condenser? As I'm interested if these swing out holders work on all BH2 condensers or just the Abbe. Looking forward with further updates.

microcosmos
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#5 Post by microcosmos » Fri Sep 24, 2021 3:15 pm

I haven't done anything like that unfortunately. I think it will be trickier as you can't just plonk it on top of something, you have to screw it on or clamp it onto the condenser somehow to prevent it from falling off due to gravity.

My design is meant to rest on top of the field lens housing like the original filter holder so it should work with any condenser since there's no contact with the condenser, unless the condenser is of such a design that its bottom goes very close to the light source when set up for Köhler illumination.

If you lower most condensers to their lowest travel limit (in order to remove them from the microscope for example) I believe they will hit the filter holder (in which case the filter holder should be removed beforehand), but if the condenser is focused for the proper illumination it shouldn't hit. I will do further testing of the filter holder when I actually get it, hopefully soon.

microcosmos
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#6 Post by microcosmos » Thu Sep 30, 2021 2:01 pm

The machined parts arrived today. To my relief, they're a perfect fit. As designed, the filter holder doesn't cover the nice engraved field diaphragm icon on the field lens housing, unlike the Olympus design which drives me crazy.

ImageImage

When it is installed on the microscope and the filters are swung out, the entire device tilts a bit because I didn't dare to make the bottom insertion pins with too close a tolerance for fear that they won't fit. But it won't fall out because the pins are long enough. The filters are conveniently out of the way behind the light source. It just doesn't look as precise as a nuclear physics experiment. If it drives me crazy I'll stick it down. I have to admit the Olympus design may be slightly better here because I believe it has a clip-on feature so it holds tight.

Image

If you want to try it out you can find more details and download the CAD files here: https://www.linyangchen.com/Olympus-BH2-swing-out-filter-holder

Machining it in stainless steel was relatively costly but I love stainless steel and since it was my own design it was worthwhile one-off for me. Others may want to do 3D printing instead, or do it in aluminium.

However, some 3D printers and printing methods may have problems with the thin parts, so you need to ask the 3D printer person to double check the file and make sure it's printable, rather than just submitting an automatic online order.

Use a material that is rigid enough for the hinge to support the weight of the trays while swung out without deforming.

If possible, also ask the workshop to check during fabrication that the hinge between the base and filter tray is a good fit and fine-tune it if necessary. It is important to make this hinge tight, otherwise the trays will tilt and be irritating, and the upper tray may scratch the filter below.

If you actually get one made, let me know how it goes!

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mrsonchus
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#7 Post by mrsonchus » Thu Sep 30, 2021 2:38 pm

I use this Olympus filter-changer that holds 3 filters, for my BX50. It slots onto the light-port then turns to be parallel to the 'scope to lock in place. It holds 45mm filters - I use it for different ND filters (as I like to have the illumination turned to full as it's Halogen) and also have a dark-blue filter in it. The BX50m has of course 3 filters built-in also..

This 'cassette' as I believe Olympus call it, works perfectly - selecting filters is so simple I don't notice I'm doing it anymore - they of course can all be selected or in combinations/singly.

The cassette
Image

Slide onto light-port's 'rim' at angle,
Image

Straighten it up,
Image

Perfect!
Image


I think this cassette (Olympus part U-FC Filter Cassette) would fit a BH2 also?
I think it's also used with blue and yellow filters for gout-crystal detection.....
John B

microcosmos
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#8 Post by microcosmos » Thu Sep 30, 2021 3:24 pm

Interesting, I've never seen it before! It will certainly solve my kind of problem.

What is the outer diameter of the field lens housing that this filter holder slots onto? I can measure mine to see if it matches.

Alas, I'm personally not a fan of this design, talking about it from an industrial design perspective - it's plastic and boxy/bulky, and it covers the field diaphragm markings which as I mentioned earlier drives me crazy.

It also seems to obstruct most of the field diaphragm adjustment ring? So it's difficult to adjust the field diaphragm when changing objectives, although you can still slide your finger along the side of the ring?

You can see that I really went for the circular compact metallic look in my filter holder - I specifically left the edges unrounded and angular, and I left the stainless steel in its raw machined finish.

But for those who're into the more modern design aesthetic of the BX series I think your filter holder matches the microscope very well and works nicely.

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mrsonchus
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Re: "Improved" version of Olympus BH2 swing-out filter holder BH2-FH

#9 Post by mrsonchus » Thu Sep 30, 2021 6:01 pm

It really is very handy, but I certainly like metal parts! The field-iris ring is definitely not obstructed though - I find now with my regular use that my fingers 'remember' where it is without needing to check at all - it's use, as most parts I think, becomes second-nature. Similarly for the stage controls, I find the super-slick Olympus focus co-ax is easily used with a single resting finger, the rest of them scanning with the dropped co-ax X-Y turns.

Having said above, is there anyone out there that doesn't find well-machined stainless-steel very satisfying indeed?!
John B

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