Research on auto-focusing of high signal to noise ratio image with weak light

摘要

For souped-up of Optical Damage Online Inspection system and obtain damage information of the optic exactly, this paper describes an auto focusing method for weak spot which on high signal to noise ratio image in darkroom. We used different calculation strategy to target pixel and adjoining pixel, compute the gray different that on x and y, compared the result of two focusing evaluation function which the gray difference absolute sum function and the gray difference quadratic sum function, select the best calculation strategy and focusing evaluation function. Test results indicate that, the gray difference quadratic sum function can be more exactly in darkroom and under weak light.