title: Robust automatic focus algorithm for low contrast images using a new contrast measure.
abstract: Low contrast images, suffering from a lack of sharpness, are easily influenced by noise. As a result, many local false peaks may be generated in contrast measurements, making it difficult for the camera's passive auto-focus system to perform its function of locating the focused peak. In this paper, a new passive auto-focus algorithm is proposed to address this problem. First, a noise reduction preprocessing is introduced to make our algorithm robust to both additive noise and multiplicative noise. Then, a new contrast measure is presented to bring in local false peaks, ensuring the presence of a well defined focused peak. In order to gauge the performance of our algorithm, a modified peak search algorithm is used in the experiments. The experimental results from an actual digital camera validate the effectiveness of our proposed algorithm.
authors.affiliation: Department of Computer Science and Engineering, Shanghai Jiao Tong University, NO. 800 Dongchuan Road, Shanghai 200240, China. xuxin0336@gmail.com
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Yinglin
authors.initials: Y
authors.lastname: Wang
authors.forename: Jinshan
authors.initials: J
authors.lastname: Tang
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
mesh_terms: D000465:Algorithms; D001331:Automation