Digital Cmos Autofocus System

Auto-focus is one kind of technology which assures imaging system of achieving high-definition image, it is used in photographic system at the early stage. As the precision instrument heading towards high definition and automatization, the field of application of auto-focus expands quickly and it becomes an essential part of microscope imaging system.In this paper, a digital CMOS auto-focus system applying to microscope is introduced and the whole stage of auto-focus is controlled by computer. The computer calculate the video signal from CMOS to get a focus value while it makes the step motor rotate and draws the curve of evaluation function. By comparing many different focus values, 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.The method of auto-focus we use bases on image processing, it's totally different with conventional methods. It analyze imaging quality of images using image processing technology to get the focusing state of system, and then drives step motor to adjust object distance to come into a focus.In this system, software is used to control the whole process, including video collecting from DCM, analysis of definition of the image, controlling rotation of step motor etc. We can watch real-time video and related information, and also modify some of the parameters. Excepting the step motor and its driver that have been fixed to the microscope, the whole system is a software system, consequently it is very convenient to use.