Auto-focus control of a CMOS image sensing module

Article type: Research Article

Authors: Kuo, Chung-Feng Jeffrey | Chiu, Chin-Hsun

Affiliations: Department of Polymer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei, 106, Taiwan

Note: [] Corresponding author: Professor C.-F.J. Kuo, Tel.: +886 2 27376535; Fax: +886 2 27908821; E-mail: jeff@tx.ntust.edu.tw

Abstract: This research is intended to establish faster and more accurate automatic focusing control for the complementary metal-oxide semiconductor's (CMOS) image sensing module. Because it would be difficult to formulate the dynamic mathematic model for the automatic focusing system, this innovative research will use the intelligent control method to manipulate the auto-focus system so as to control the motor rotating angle to move the lens position for achieving the auto-focus purpose of the CMOS image sensing module. In this respect, the modulation transfer function (MTF) is used as a key indicator to describe the developing quality of the image system. By using the image sensing module, this research will retrieve the MTF for examining graphic image and the change of MTF is used as the input parameters of the fuzzy controller. After the fuzzy rule base and the membership function are established, by the process of fuzzy inference, actual rotating angle of the motor will be obtained by defuzzifying the fuzzy output so as to achieve the auto-focus purpose for the CMOS image sensing module. The performance of an improved membership function for this fuzzy controller can be effectively shown through the experiment.

Keywords: Fuzzy controller, auto-focus control, modulation transfer function, automatic production line

Journal: Journal of Intelligent & Fuzzy Systems, vol. 18, no. 4, pp. 405-415, 2007