CMOS photoelectric image sensor

      CMOS (Complementary-Oxide-Semiconductor) image sensor appeared in 1969, it is a traditional chip process method to integrate photosensitive components, amplifiers, A/D converters, digital signal processors and computer interface circuits on a single silicon wafer image sensor device, this device has a simple structure, many processing functions, high yield and low price, and has a wide range of application prospects.

      Although CMOS image sensors are one year earlier than CCD, they can only be used in digital cameras with low image quality requirements and small size, such as robot vision applications, due to its poor image quality, small image sensitivity unit size, low filling rate (effective pixel to total area ratio) (10%-20%), and slow response speed. Early CMOS devices adopted a "passive pixel" (passive) structure, and each image-sensitive unit was mainly composed of a photosensitive component and a pixel addressing switch, without signal amplification and processing circuits, and poor performance. After 1989, the "active pixel" (active) structure appeared. It not only has photosensitive components and pixel addressing switches, but also has signal amplification, digital-to-analog conversion and digital processing circuits, which improve photoelectric sensitivity, reduce noise, expand dynamic range, and make some of its performance parameters close to CCD image sensors, and are better than CCD image sensors in terms of function, power consumption, size and price, so it is more and more widely used.

      CMOS image sensors are mainly composed of photoresist diodes, MOS field-effect transistors, amplifiers and switches. Therefore, the basic principle and main performance parameters of MOS field effect transistors are first introduced, and then the structure and working principle of CMOS image sensors are described, and the main performance parameters of CMOS image sensors and their improvement methods are discussed. Finally, some typical CMOS image sensors and typical CMOS digital cameras are introduced