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Comment by frostburg | Hacker News Reader

I've built variants of these years ago for a school. The positioning system works extremely well, especially given the fact that it is 3d-printed; the optics were rather limited, both by lens quality and by the use of the old rasperry pi camera sensor.

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I've looked into building a "high resolution optics" version. Most parts [1] are easily sourceable, but the tube lens [2] has proven to be difficult.

It seems half inch diameter, 50mm focal length achromatic doublets are not that common; Thorlabs does seem to be the only source, and are (at least at the moment) not in stock.

[1] https://build.openflexure.org/openflexure-microscope/v6.1.5/...

[2] https://build.openflexure.org/openflexure-microscope/v6.1.5/...

Compatible 50mm achromatic doublets are not that common? That part needs a redesign...

Since you've done the research, I hope you don't mind me asking (I have little to none formal knowledge in optics).

I am trying to build a homemade projector, I was looking for what I think is a 'broadband' (visible light) 'non-polarizing' 50:50 beamsplitter but all the beamsplitters I found are quite expensive. Is there a 'lower quality' hobbyist-grade product range of beamsplitters that you could point me to? (Brands or distributors is also fine)

I'm certainly no expert, my knowledge is limited to what I picked up after a few nights of reading about the microscope.

Does the beamsplitter have to be non-polarizing? My understanding is that standard beamsplitters do the splitting by polarizing the incoming light.

Now that I think of it, you're probably using a standard display as your image source? That does indeed produce polarized light. In that case I would try a (common in photography) circular polarizing filter. Rotate the filter to match the display polarization, after that the light will be circularly polarized. I think you could use that in combination with a "standard" polarizing beamsplitter. Depending on the desired dimensions, there are a few available on aliexpress.

Thanks for the pointers, I had assumed non-polarized was a requirement but indeed didn't consider that display sources are themselves polarized.

Thanks for the firsthand report. It occurs to me that optics have not gone through any of the disruptions that electronics have. It’s still difficult to find good lenses at a student budget price.

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