Programmable gain CMOS photodetector array for a non-diffractive beam optical encoder

In a previous paper presented at EAMTA 2011 our group introduced the design of a customized CMOS active pixel sensor (APS) for a non-diffractive beam optical encoder implemented in a standard 0.5 μm channel length CMOS process. In this work we bring up a new version of the chip endowed with a programmable gain system that allows weighting the light collected by each pixel by a programmable factor between 0 and 127. By means of experimental measurements the performance of the chip is studied for light intensities varying over three decades and gain factors varying between 0 and 127.