I have found small infrared detectors in VCRs that I have dismantled.
I've used them to operate crossing gates and flashers. Most are about 1/8"square, I've seen them as small as 1/16".
Would something like that work?
of course, small also means quite expensive. full systems With amplifiers, power supplies, sensors and fiber cables start around US$350, and can go up to US$3,500.
I have taken senors out of VCR's. I have even built the contol cuircits for it. It's a pain in the a@# to fine tune! I replaced them with Banner Optical senors, but they are too large for the coffee table!
I have check out the links, thanks guys! I have bookmark them all.