A PHOTOSENSOR ARRAY FOR SPECTROPHOTOMETRY

A monolithic intelligent CMOS photosensor array specifically aimed at spectrophotometry is presented in which a linear photodiode array is integrated together with a charge amplifier, an analogue-to-digital converter, a digital programmable polynomial solver for pixel-level calibration, a set of control registers and a processor interface. This architecture reduces noise effects by using large pixels and by closely coupling the analogue-to-digital converter to the photosensors. This also simplifies the user interface as all analogue circuits are on chip. A digital polynomial solver performs pixel-by-pixel calibration to compensate for source, transmission medium and sensor nonlinearities. Low power consumption and 5 V operation render the sensor suitable for portable applications. The sensor was fabricated in a standard 1.2 mu m analogue CMOS technology with added light shield.