Imaging Without Lenses

Re:Imaging Without Lenses by anfractuosity on Monday February 05, 2018 @11:38AM (#16309910)

I'm curious if you could DIY the mask used for example in FlatCam that they mention, it looks a really interesting area.

Apparently for the mask they use "a custom-made chrome-on-quartz photomask that consists of a fused quartz plate". I was wondering if you could make a very poor equivalent through just acetate and printing.

It vaguely reminds me of an old fashioned technique such as:

https://en.wikipedia.org/wiki/Zone_plate

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Re:Imaging Without Lenses by stochastician on Monday February 05, 2018 @02:14PM (#16311179)

You can actually just place a random diffuser directly on a sensor -- this is work from some colleagues at UC Berkeley which I (surprisingly) didn't see mentioned in this article https://www.medgadget.com/2018/01/diffusercam-lensless-3d-im...

DiffuserCam was previously discussed on HN but I couldn't find the link.

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Re:Imaging Without Lenses by anfractuosity on Monday February 05, 2018 @03:56PM (#16312101)

Cheers, I'll have to look more at that. It's neat the source is available too!

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Re:Imaging Without Lenses by michrassena on Monday February 05, 2018 @12:16PM (#16310249)

This article the first instance I've heard of placing the mask directly on the sensor. I'd always had the impression that the coded aperture would be substituted for the original lens aperture. And the images I've found online seem to indicate that the aperture is macro-scale. This is something which could be imaged on lith film or hard-dot film.

I'd really like to play around with these techniques, but I don't know where to start. The only deconvolver I could find used Mathematica, so I'm not sure how useful making a coded aperture would be if I couldn't see the results.

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Re:Imaging Without Lenses by robbystk on Monday February 05, 2018 @12:27PM (#16310323)

You can do deconvolution using ImageJ, but getting a model of the PSF for an arbitrary aperture is the tricky part. https://imagej.net/Deconvolution

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Re:Imaging Without Lenses by michrassena on Monday February 05, 2018 @02:27PM (#16311295)

Would it be as simple as imaging a point with the system and using that as the source for the PSF?

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Re:Imaging Without Lenses by lp251 on Monday February 05, 2018 @03:14PM (#16311692)

more or less; the flatcam paper has a section on the calibration method (finding the psf)

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Re:Imaging Without Lenses by michrassena on Monday February 05, 2018 @04:00PM (#16312138)

In this article, they talk about encoded blur.

http://web.media.mit.edu/~raskar/Mask/

About halfway down the page you can see the out-of-focus point source looks identical to the coded aperture.

While not lensless photography, this seems like a good starting point for those interested in these techniques, especially if I can load the PSF into ImageJ.

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