Study And Implementation Of FPGA On Lens Illumination Compensation Arithmetics

Currently, digital imaging, such as laptop, PAD, digital camera, cellphone and thesehandheld electronic devices, are usually made based upon the CMOS image sensorstechnology. While the raw image from the CMOS image sensors could not be useddirectly, there exist a plenty of quality defects like image brightness nonuniformity andthe edge of a lack of brightness, which would require the processing of image processorsto get satisfying result.The article firstly conducted the thorough research to the lens illuminationattenuation causes. As a part of image processing, lens illumination compensation aimsat improving the luminance uniformity of the raw image, especially the shading in theedge parts, eliminating the brightness difference between the image center and edgeparts resulting from the depression of lens illuminance, and ensuring the integrality ofthe image information. This design employed piecewise linear compensation, high-ordercurve fitting technique to improve the smoothness of the fitting curve, moreover, thedisposed image is more uniform than that dealing with piecewise linear processing. TheMATLAB software is used to write the illuminance compensation arithmetic and adjustthe arithmetic and parameters according to the in-time image processing. The arithmetichas been proved to be easily calculating and adjusting. Utilizing Verilog language todesign the algorithm, which give the data flow diagram and the actual compiledtop-level module diagram. Approximate calculation method of easy hardware realizationis introduced in order to reducing chip area and lowering power consumption. Thedesign results meet the requirements of the algorithm. Power optimization has achievedby the operand isolation and clock gating technique.The test of the processed image using the Imatest software has proved that thearithmetic in this design had accomplished the purpose of lens illuminance correction.Comparing to the preprocessed image, the processed image has gotten a much betterbrightness smoothness degree, which has met the quality demand that the brightnessdifference between the image center and edge should be less than20percent.