An Auto-focus Research Based On Portable Photo System

Auto-focus is one of the key problems in machine vision and imaging systems. It's crucial to many application areas where involve with imaging system, such as daily life, science research, military affairs. First, this paper briefs the principles and characteristics of auto-focus, then digs several techniques—evaluate functions, focus windows, focus searching algorithm and control of lens, which surround auto-focus system. According to its principles,characteristics and techniques, an auto-focus system based on portable photo system is put forward.In this paper, in order to improve the precision and the speed of auto-focus, the green components of images and amendatory gradient formula are used to calculate the evaluate functions, we compare the effect of three evaluate functions that process images on PC, and confirm the best one; the method based on golden section is introduced to select the focus windows; on the basis of thoroughgoing research of the conventional mountain climbing algorithm, we propose a modified mountain-climbing algorithm to achieve better focus effect. The auto-focus system is implemented on the portable photo system based on the microprocessor S3C44B0X. We increase the work efficiency of the portable photo system by improving the precision and speed of auto-focus in the system.Two working methods—digital aided manual focus and auto-focus are used in this system to carry on a choice according to the different demand, automatic follow focus is also used in this system for auto-focus when the target changes.Finally, an auto-focus system based on portable photo system has been designed and constructed. The results show that the system has excellect focus effect,high focus stabitity and dependability. Main conclusions of this paper have been summarized, and the prospects and study emphases of further work have been forecast.