I ordered one of the TSL235R chips when I was getting an AVR programmer, and made a quick video about it. One of the comments on the product page had suggested it could be used as an optical theremin. Someone replied that it was an interesting idea, and that they were going to look into it, but never replied back. So I tried it out.
Ehh, not so much… most of the frequencies you get waving your hand in front of it are quite high and annoying. So while it does work as a theremin, it’s wouldn’t be practical as a theremin, unless you added a frequency divider or something.
I also talk briefly of the project idea I had in mind for the TSL235R, a Laser Scanning Microscope. Somewhat inspired by Ben Krasnow's Electron Scanning Microscope, I found that my green laser pointer radiated different amounts of light depending on what color it hit. If I measured that radiant light, I could convert those values to a grayscale image. I just so happen to have a Laser scanner I bought off eBay years ago, so I was thinking I could use a DAC with an Arduino to controller the scanner, and pickup the light values with the TSL235R. By projecting the scanner through a microscope, I would effectively (or to be precise, ineffectively) create a Scanning Laser Microscope, somewhat similar to the actual 'Confocal Laser Scanning Microscope'.
http://en.wikipedia.org/wiki/Confocal_l ... microscopy