Near-Sensor Image Processing

Abstract

This chapter discusses the concept of near sensor image processing (NSIP). The photoelectric effect is the basic physical principle used in all light sensors. Under certain conditions, it is possible for a photon that hits a material to leave its energy to an electron. This causes a charge to build up in the sensor material. In a charge-coupled device (CCD), photo element used in many TV cameras, the charge is collected in a well created by applying suitable voltages to a system of electrodes. The sensors are interrogated at even or uneven time intervals in the main NSIP loop during ongoing exposure. In NSIP, the exposure time depends on the light condition as it is exposed until at least one position accumulates enough light energy. Thus, tolerance to various light conditions has been traded for data-dependent non-fixed exposure time. To obtain such adaptation in traditional systems, an outer control loop is needed to modify the exposure time and maintain a reasonable signal-to-noise (S/N) ratio. All this comes free with NSIP.