This part is a kind of semiconductor called AEDR-8400.
Function of this product has Reflective Surface Mount Optical Encoder.
Manufacturers : AVAGO TECHNOLOGIES
Image and pinout :

Some of the text within the PDF file :
AEDR-8400 Series Reflective Surface Mount Optical Encoder Data Sheet Description The AEDR-8400 encoder is the smallest optical encoder employing reflective technology for motion control purposes. The encoder houses an LED light source and a photo-detecting circuitry in a single package. The AEDR-8400 encoder offers two-channel quadrature digital outputs. Being TTL compatible, the outputs of the AEDR-8400 encoder can be interfaced directly with most of the signal processing circuitries. Hence the encoder provides great design-in flexibility and easy integration into existing systems. Features • Reflective technology • Surface mount leadless package • Two channel quadrature digital outputs for direction sensing • TTL compatible • Single 2.8V sup [ ... ]
AEDR-8400 PDF Datasheet Download
