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some tricky fresnel lens question


lequitywk

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Well this thread title sucks, sorry.

I have a plano convex lens (actually equivalent stack of two fresnels each with focal length 120mm, groove pitch: 0.3mm).
If I put a photo behind it at a 45mm distance and view through the lens from a 21mm distane, I get perfect focus in the middle area.

I am able to correct the spherical distortion by adding a pre-distortion to the original printed photo in photoshop.

Similarly I can reduce the chromtic aberration in a similar way.

What I can't do is get things on the edges in focus as well.

The lens is flexible and bendable.
So is the material the photo is printed on.

What kind of geometic distortion should I apply to the fresnel lens and the photo frame to achieve uniform focusing?

I am picking up where these researchers left off. http://www.cs.ucsb.edu/~mturk/pubs/IsmoICAT-EGVE2016.pdf

The bending of the lens as illustrated in that research paper seems the ideal fresnel lens bended shape to me, that is, if they also bent it in the other axis.
https://i.imgur.com/WKw35Y3.png

The original authors seem to have disregarded actual optical distortion and went with trial and error and (quoting) "good enough" results.

Even though we do not have the technology of custom shaped screens (not just bendable in one axis at a time) and may not ever, this can still be used for a full FOV stereocope ( https://en.wikipedia.org/wiki/Stereoscope ). I am not aware of one existing to date.

I could write some software in Python to take stereo data and convert it to properly pre-distorted frames to be printable on a vacuum formable photo frame sheet. The thin fresnel lens are also vaccum formable and simply bendable. So anyone wanting their own complete FOV stereoscope can build one for very cheap. Seems fun but the optical distortion calculating part for achieving uniform focus is beyond my expertise, if anyone wants to chime in with a distortion/3d shape for the fresnel lens and photo frame, that would be awesome.

Edited by lequitywk
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