Definition evaluation function of digital image in autofocusing system

FENG Jingwu1, YU Qingcang2, LU Ning2, FENG Haiming2
(1. Faculty of Mechanical Engineering & Automation, Zhejiang SciTech University, Hangzhou 310018, China;
2. College of Electronics and Information, Zhejiang SciTech University, Hangzhou 310018, China)

Abstract: In order to slove the problems of autofocusing technology based on image processing, it is the key step to use the accurate and effective functions. The role of Gradient function, Spectrum function and Entropy function in autofocusing system was analyzed and compared by experiment in autofocusing system. The performances and features of these functions in experimenteral platform were studied. Experiments results indicate that Tenengrad function, Brenner function and Square Gradient function has high sensitivity features in focal plane, when defocus serious, the tread of change is not clear, this can be applied in accurate focus equipment .Variance function has good SinglePeak and sensitivity, characterize the preferable efficiency, has high singletonoise,better reliability, than other ones. It can better meet the requirement of the image definition evaluation, can be applied in digital image autofocusing system.
Key words: image definition; automatic focusing; evaluation function; focal plane