Zoom Lens Automatic Focusing Technology Research

This paper mainly discusses the whole design process of the cun-ent widely applied to zoom lens auto focus system, from hardware to software programming design, including the design of hardware and software program. First, the CMOS image sensors collect video image information, then deal with the collected signals by digital signal processor (DSP) and related peripheral circuit, get the specific focus value evaluation function though fited algorithm, find the focusing position using optimization of the hill-climbing searching arithmetic, and finally make the CMOS moved to the position of the focusing accurately using DSP chip. The video signal from digital CMOS image sensor is calculated in DSP to get a focus value, and then the proper focusing position is found using optimized hill-climbing searching arithmetic, the step motor will drive the lens to this position to get a well focused image. When zoom lens changes zoom rate, according to the variable the rate and specific skills can also completed the function of auto-focus. Overall design scheme of this system is also applied to other equipments that need auto-focus technique, such as digital camera, microscope and vidicon etc.The hardware of this paper is mainly made up of zoom lens, digital image sensor, digital signal process system, USB communication interface, stepping motor and its driving system. The software includes the algorithm of DSP signal image processing, optimized HCS(hill-climbing searching),and the program of step motor driving, USB communication interface.