In the upper left, I know it’s a light sensor of some sort–but unlike any I’ve seen before. I can also post a full 4k res picture.
http://imgur.com/0Igwj.jpg (Bigger)
It looks like a silicon light sensor.
Yep, either a photo diode or a photo electric cell.
What voltage does it put out with exposeure to brignt light?
Maybe its like one of these:
Its a photodiode. Note that it appears to have a cut filter glass in front of the element, possibly making it a PAR (Photo-synthetically Active Radiation) sensor (to cut the IR segment out and shift the peak response).
Hamamatsu makes the PAR variants: http://www.hamamatsu.com/
Thanks for that Hamamatsu link–that’s perfect!