A CMOS image sensor zero power dynamic range increasing technique

A development of in-pixel dynamic range (DR) increasing technique without charging extra power for CMOS image sensor was realized in this paper. Recently, many researches reported that high dynamic range can be achieved through processing the image signals with ADCs or counters built inside the pixel, and some other methods require adjustable circuit block to maneuver photo-generated charges by a longer integration time. However, the inevitable consumption of power due to additional circuits alleviates the practicality. In this paper, a CMOS image sensor based on 3T active pixel sensor (APS) with 5.5 ¿m pixel pitch is investigated, successfully increasing DR without charging additional power by implementing a total of 4 sets of image arrays, of which 3 are new designs and one is typical type as control group. The arrays are 32 × 32 pixels, implemented in a 0.18 ¿m CMOS fabrication process, where photodiode has an n-well and p-substrate structure. Testing result is an increment of DR by estimated 7 to 18 dB among the experimental groups with no power consumption. The idea of in-pixel DR enhancement technique is verified, and one conclusion is made that in-pixel analog design is one direction for designers.