A DPS array with programmable resolution and reconfigurable conversion time

A CMOS digital pixel sensor (DPS) with programmable resolution and reconfigurable conversion time is described. The chip features a unique architecture based on the pulse width modulation (PWM) technique and operates with either an 8-b or 4-b accuracy. The 8-b conversion mode is used for high-precision imaging while the 4-b conversion mode provides a shorter conversion time and a two times increase in spatial resolution. Two quantization schemes are studied, namely, the uniform and the nonuniform time-domain quantizers, which are referred to as UQ and NUQ, respectively. It is shown that the latter scheme not only permits to linearize the nonlinear response of the PWM sensor, but also allows to significantly speed up the conversion time, particularly for wide dynamic range and low coding resolutions. A prototype of 32/spl times/32/64/spl times/32 pixels has been fabricated using 1-poly, 5-metal CMOS 0.35-/spl mu/m n-well standard process. Power dissipation is 10 mW at V/sub DD/=3.3 V, dynamic range is 90 dB, while dark current was measured at 1 pA. The reconfiguration features of the chip have been verified experimentally.