A self-adjusting Lin-Log active pixel for wide dynamic range CMOS image sensor

Due to low cost, low power consumption and better on-chip functionality CMOS Image Sensor has become the main image sensor for consumer electronics, machine vision as well as in research applications. Besides the advantages, a CMOS image sensor suffers from noises, less sensitivity as well as lacks of Dynamic Range (DR). Logarithmic response Active Pixel Sensor (APS) is a solution for wide dynamic range imager maintaining high fill factor. 3T Linear APS (Active Pixel Sensor) has better performance in low illumination, but very poor sensitivity in low illumination. For 3T logarithmic APS has satisfactory performance in high illumination, but limited sensitivity in low illumination. Few reported to implement both linear and logarithmic capture for a single frame which increases the capture time. Implementation of in-pixel circuitry to combine both linear and logarithmic in a single capture which decreases the fill factor of the pixel is also reported. In this paper, we propose a self-adjusting pixel to combine linear and logarithmic response maintaining high fill factor. The proposed pixel was simulated in Cadence Virtuoso in 180nm technology node and analyzed for comparative study of dynamic range.