%0 Journal Article
%T Robust Automatic Focus Algorithm for Low Contrast Images Using a New Contrast Measure
%A Xin Xu
%A Yinglin Wang
%A Jinshan Tang
%A Xiaolong Zhang
%A Xiaoming Liu
%J Sensors
%D 2011
%I MDPI AG
%R 10.3390/s110908281
%X 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.
%K auto-focus
%K low contrast
%K contrast measure
%K noise reduction
%U http://www.mdpi.com/1424-8220/11/9/8281