Study on image focusing algorithm and realization of FPGA

The key to focus automatically using the image processing method is to take the character of image definition and to establish its evaluation algorithm. The paper studied the preprocessing methods, such as the linear transform of gray value, the gray histogram equilibrium, the median filter, the homomorphic filter, and the image definition evaluation function based on power spectrum. The evaluation method was analyzed and compared with other methods. The results indicate that the preprocessing method of combining the median filter with the linear transform of gray value is good in effect, little in calculation and so on. The image definition evaluation function based on power spectrum is superior in focusing performance and more definite in physics meaning to other methods. According to the characteristic of the image focusing algorithm based on power spectrum, the structure frame and algorithm flow of the image processing module were designed, and the implementation solution of the pipelining structure, the 'ping-pong' working mode, the sharing processor of double butterfly shape and the base-2 FFT algorithm in FPGA were presented in this paper. The above-mentioned measures can improve the computing and response speed of the image auto-focus.