This is an industrial grade defuse photoelectric sensor module which is based on Optical IC S8119 from HAMAMATSU. A diffuse reflection sensor is used for the direct detection of an object. The defuse reflective sensor project consists of an Infra-RED LED and receiver. The IC also provides output pulses to the IR LED which emits IR- light which is reflected by the object to be detected and seen by the S8119 IC. Both the emitter LED and receiver sensor are placed on same PCB and are configured for light to be reflected back to the sensor.
Photoelectric Defuse Sensor using S8119 – [Link]