Abstract
This thesis describes a wide dynamic range dual exposure CMOS image sensor with illumination detection scheme to extend the dynamic range, and synthesize the images into a wide dynamic range scene without post signal processing. There are some innovations in this thesis. First, a novel operation for conventional 4T active pixel sensor is proposed so that it can proceed long exposure time and short time in a frame time, and does not require any external image processing to synthesize the wide dynamic range image. Second, an illumination detection scheme is used to reduce the fixed pattern noise (FPN) by process variation in above operation. By detecting the partial signal in the integration time, it can determine the illumination condition of the sensor. It provides a tunable transition point by using different exposure ratios and Vmid, making the sensor to obtain the best image quality in different environment. The prototype wide dynamic range dual exposure readout CMOS image sensor chip is composed of a 128×128 4T-pixel array, and the pixel pitch is 6×6 um2 with 32%fill factor. It was fabricated in TSMC 0.18um 1P6M CMOS image sensor process. A prototype 128×128 imager employed these schemes experimentally achieves 98.9 dB dynamic range with the exposure time ratio of 144. Compared with conventional 4T-APS without these schemes, it increased 37 dB of dynamic range. The column FPN is 1.07mV (0.097%), and the pixel FPN is reduced from 97.4mV (8.85%) to 18.2mV (1.65%) under high illumination condition.