FPGA-based parallel calculation of focus function

Auto-focus systems always suffer from the problem of poor sensitivity of focus functions and long focus time. This paper proposes an adaptive method with FPGA to solve this problem. The method is based on image block region, which brings about two advantages. One is that the weights can be set for each image block; this will enhance the sensitivity of focus function. The other is that each image block can executes the image process in parallel; this will improve the speed of focus. This paper has also analyzed and compared several classical focus functions, and then constituted a focus function based on Brenner method. This paper proves that the parallel calculation method of focus functions needs less time that can improve the reliability and response sensitivity of auto focusing process.