High linearity current mode image sensor

Abstract

Current mode image sensors enable an easy implementation of focal plane algebraic functions, but suffer from poor linearity performance. A theoretical analysis is first performed on the source of the non-linearity for current mode image sensors. According to the analysis, an architecture of a current mode image sensor with a voltage feedback loop between pixel output and the current conveyor for linearity enhancement is proposed. An image sensor array of 100 × 200 current mode pixels is fabricated in 0.5um 2P3M standard CMOS processing technology. Experimental results illustrate a 45% improvement of the linearity of the proposed imager. Fixed pattern noise is reduced by 19% at the saturation level and signal to noise ratio of 49.6dB is achieved.