Intro to Fourier Optics and the 4F correlator
My physics professor showed me this in the lab one day, more than 50 years ago now. He used black and white microfilm and microfiche. He showed me newspapers on microfiche that could be searched for specific things. Your clearer explanation of how to use the “amplitude only” part of the spectrum to make the information location-independent was helpful. There will be geometric issues I think, but that helped clean up an old memory. I have over the years kept an eye on this, and now there are micro-mirror arrays, and many controlled transparency materials to generate the spatial filters using the computer.
Nothing was ever cheap enough for me to try it. It seems everything that is interesting quickly becomes costly. But your videos are a good “buy” because you are always trying to show how things work and how to built them and understand them. I can think of a few things to try, but there is no way to interact on YouTube, except by quickly disappearing text notes.
Thank you for your work. I just watched an old Raman spectroscopy video of yours where you said you were going to get back to it, but I could not find it. I really liked what you showed with the pinhole. I wish you had spent more time. I want to find a way to spread out the intense points in a better way. Bessel beams and optics seems a good path. I am getting older and there are billions of things to look at and try to calculate. I can’t build anything, mostly too costly or too hard. But I can calculate most anything. Go figure.
Richard Collins, Director, The Internet Foundation