An auto-focusing method based on image processing technique

In order to improve the image processing precision and the performance of system, an auto-focusing method based on image processing technique is proposed. An improved grayscale difference function was employed in the novel method as the selection function of auto-focusing. It offers great characters of focus sensitivity and edge information. Based on the analysis of noise in the image signal, linear fitting and homomorphic filtering were employed as the signal pretreatment. It is an effective method to get the defocusing information from the judgment function. A new searching step based on the value of auto-focusing function is proposed, which follows the auto-focusing judgment function result to modify the searching step. The experimental results show that the algorithm proposed manages to focus correctly in the range of +/-200 mum by variable step searching, and the precision is up to +/-1 mum.