Design Of Automatic Exposure Circuit Based On CMOS Image Sensor Chip

Currently, CMOS image sensor applications are very broad, from the video phone, fingerprint identification, digital cameras, automotive to medical electronics, and even aviation. The trend of CMOS image sensors is integration, ultra-miniature, intelligent, high-resolution, wide dynamic range, and high frame rate. In particular, ISOC (the image sensor system on chip) is a new research direction in recent years. Automatic exposure function changed exposure parameters according to the scene, take pictures and then adjust the brightness. Image brightness is the most intuitive understanding of image which plays a vital role in the quality of the image, it features automatic exposure for the CMOS image sensor system one of the most important functions.This paper mainly discusses the design and hardware implementation of the automatic exposure control circuit based on the CMOS image sensor system. Introducing the latest research progress and the principle of exposure, from the metering means, the choice of color space, the position of auto exposure module in the pipeline, target identification, etc. discussed in detail the algorithm and hardware implementation of the auto exposure which based on dynamic step considering the target iterative algorithm. Improved iterative step can quickly achieve more accurate exposure adjustments, and gives the MATLAB software verification results. And in order to improve the imaging results, increase the exposure compensation module for high contrast scenes when arise the overexposure and underexposure, the detection method using fuzzy logic. Also increased Flicker detection module for indoor lighting phenomena when often occur flicker, using two amplitude difference calculation method, the image sensor in the indoor lighting can also work well. Using Verilog hardware description language design, simulation and debugging, automatic exposure module is divided into the main module, exposure compensation module and Flicker detection module. Using Quartus FPGA integrated for a total consumption of 2778 logic elements and 8192 memory units. Test in the CMOS image sensor image processing system. System includes an Altera FPGA chip EP1C12Q240C8, a 128Mbits of SDRAM, a 2Mbits asynchronous SRAM and a Cypress of USB2.0 controller chip CY7C68013. In the system, the whole module and the sub-modules work correctly, can quickly and accurately adjust the exposure parameters according to the scene so that the brightness of the image to the appropriate value. In the interior lighting and high-contrast scenes the exposure effect can also be improved to achieve the design requirements.