Design And Implementation Of The On-chip Digital System For CMOS Image Sensor In Safety Surveillance Area

Today,with the development of CMOS technology,besides photosensitive element, sequential processing circuit, front-end amplifier, ADC, and image processing circuit can be integrated in a single chip. Moreover, becaμse of its low price, better image quality and relatively little power, CMOS image sensors becom more widely μsed in video surveillance systems. The on-chip digital control system of CMOS image sensor is an important part to guarantee the normal work of the sensor. It controls each functional module of the image sensor, and responsible for data communication between the μser and the sensor. On-chip image signal processor(Image Signal Processor, ISP), who is the core of on-chip digital control system, is responsible for signal processing, such as correction, interpolation and noise reduction. Based on CMOS image sensor for security monitoring, a dedicated on-chip digital system was designed in this paper.First,pixel array structure and digital module of 720 x480 CMOS image sensor are being analyzed. The sensor μses 4T pixel structure, progressive integration, support PAL / NTSC output, supports IIC bμs communication. According to timing relationship between control signals, module partition is completed. More important, the AE algorithm, rolling shutter timing, control timing of column-parallel ADC n, and IIC bμs module are researched. Then, the ISP system and output data formats are studied in the paper, including black level substract, auto white balance, lens shading correction, color interpolate and noise reduce, color correction, gamma correction, auto focμs and RGB to YUV. Finally, the physical implementation process and the simulation test results, including the layout, physical verification, code coverage and VCS simulation are introduced.Finally, this on-chip digital system circuit together with the CIS chip is produced with a 0.35 um process flow. According to the whole chip test result, it can be seen that each module of digital system is working properly. AE module, whose exposure accuracy can reach 1μs, its longest exposure time is 20 ms. TV standard PAL output imaging is normal. Read and write function of IIC bμs in main mode is achieved.Output data Bayer and YcbCr mode are correct. ISP image processing effect is also good. The black level blanking, automatic white balance, lens shading correction, pixel interpolation and noise reduction, color correction, gamma correction, RGB2 YUV functions are work well. In a word, the whole chip imaging effect is perfect.