I am a new OpenFlexure user and recently set up an OFM with the high-resolution option for my work. I work for a composite products manufacturer and we wanted a better way to examine glass fibers in as-molded products. The primary purpose for us is to survey the distribution of fiber lengths (anywhe…

Hi @ryantheengineer that is an interesting application. Could you post some pictures of your set-up? I am not quite clear from your post whether you have now got the achromatic tube lens in the optics module. If you have not, then that is likely to be a big part of the issue. If you have the tube …

Hi @WilliamW , thank you so much for your prompt and helpful reply. I got sick the evening after posting my question, and I’ve just gotten back to work so I will try to make more sense of things now. To clarify my setup, my benchtop test did not include the achromatic tube lens, but my OFM does have…

With the LED and no lens the illuminated area is huge and that is not the problem. It looks most like a vignetting from the field of view of the objective, and it is off-centre. If that is not a defect in the lens, then it suggests that something in the optics module is not straight - the objective…

The last image where I showed glass fibers was the best image I could get while holding the light high above the OFM. It’s not so much vignetting as it is misalignment of the light with the optical train. That being said, I believe I’ve found my problem, which is twofold: The stock lighting is si…

[image] ryantheengineer: I’m not sure why #2 would be the case, as I thought DIN-standard objectives all have the same parfocal distance There are a lot of non-standard par-focal distance objectives. This is particularly the case for low magnification or for ‘metallurgical’ objectives.

The tube length is 160mm on the specs. And it’s “DIN standard” so parfocal should be 45mm. If it was 35mm parfocal then it would need to be a lot closer than you are saying I would think. This might be that the effective path length inside the optics module is wrong. Are you sure the achromatic tu…

@j.stirling The tube length is evidently still 160mm. I ordered my achromatic tube lens from AliExpress and it was listed as 50mm focal length. I have verified that it is fully seated into the optics module. I ended up altering the parfocal distance parameter in the OpenSCAD and printing a version …

I’m glad that everything was parametric enough for you to fix! I would assume that it is more likely that the AliExpress vendor sent the wrong tube lens is the wrong focal length than Amscope objective is 2.5mm off the nominal parfocal length The tube lens being wrong would change the effective tu…

Just in case this is useful, if you’re working at low magnification the condenser lens is possibly unhelpful. If you remove the condenser lens, this might already improve things. It’s possible that replacing the condenser lens with a diffuser (e.g. a disc of paper or thin white plastic) might be bet…

First time setup with 4X objective - Not performing as expected

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ryantheengineer 22 October 2025 14:46 11

@r.w.bowman I ended up changing out the illumination entirely. You can see what I did on this thread.

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First time setup with 4X objective - Not performing as expected

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