An auto-focus algorithm based on image processing

A coarse and fine combined fast search and auto-focusing algorithm was suggested in this paper.This method can automatically search and find the focal plane by evaluating the image definition. The Krisch operator based edge energy function was used as the big-step coarse focusing, and then the wavelet transform based image definition evaluation function, which is sensitivity to the variation in image definition, was used to realize the small-step fine focusing in a narrow range. The using of the TMS320DM642 digital signal processing chip as the platform of the focusing mechanism realized the application of the digital image processing based auto-focusing method in the optical measure equipment in range. The experimental results indicate that this algorithm can realize the image real-time focusing of the optical measure equipment, and the accuracy of this focusing system is ± 0.02 mm.