Abstract
A CMOS image sensor with light intensity filtering feature for realizing image thresholding is proposed. The simple sensing pixel circuit with less than 5 transistors is designed to provide a tunable non-linear photo-response with a peak signal at a specified intensity level. This unique intensity-filtering photo-response characteristic is achieved by push/pull forces between an n+/p-sub photo-diode and the parasitic p+/n-well parasitic diode of the PMOS control transistor. With proper timing control of this new pixel circuit, tunable intensity filtering transfer functions can be obtained. Based on the behavior model of the pixel’s photo-response, image thresholding function is successfully demonstrated by this non-linear imager.