SMART OPTICAL SENSOR SYSTEMS IN CMOS FOR MEASURING LIGHT-INTENSITY AND COLOR

An optical sensor system with digital outputs, operating in the visibl e part of the spectrum, has been developed in a standard CMOS process. The photodiodes operate in the charge-integrating mode. Two methods h ave been used in the sensor system presented here for on-chip analog-t o-digital conversion, namely voltage switching and capacitor switching . The output signal is a bitstream or a digital word proportional to t he intensity of the incident light. Information about the intensity an d the spectral distribution of the impinging light is obtained by swit ching between two PN junctions at different depths in the silicon and readout in two measurement cycles. (C) 1998 Elsevier Science S.A. All rights reserved.