Having taken apart a lot of PC mice, I can tell you with confidence that that's a optical PC mouse circuit board. Take a look at all these other mouse PCBs; you can see how similar in construction they all are.
The chip in the middle is an optical sensor. I googled it for its datasheet ("S5008"), but couldn't find any. Instead, some results hinted that the chip is a clone of the Avago ADNS-5000 optical mouse sensor (datasheet here; must be downloaded).
The image of the chip in the datasheet looks exactly like the chip on your circuit board:
As for a schematic, you can have a look at the application circuits in the datasheet of the chip, under Typical applications. That's the closest you can get to the actual schematic of your PCB, unless you do some reverse engineering yourself: