Electronic Switches (I) P. Ltd; offers Diffuse Scan Sensor in 18 mm dia; Brass housing with 100mm / 300mm range. Units operates  on 10 - 30 V DC supply. Sensitivity adjustment is available in the unit  to adjust  the required range.  Range of the sensor is 100 mm or 300mm.

 

It is 4 wire type sensor with output NPN and PNP with  NO or NC selectable.