The Autofocus System Design, Dsp-based Microscope

In this paper, based on the research and analysis of the auto-focus algorithm and status quo, a microscopic auto-focus system based on DSP is designed and it can be used in several kinds of microscopes. In this design, the video captured by electrical eyepiece is transferred to Television monitor for observation, meanwhile the imaging signal is decoded into digital data. As the core of the system, The DSP samples the digital data and storages it according to the design of sampling window, and then it calculates the data, analyzes the imaging by the merit function and searching algorithm to get the search direction and the focus position. By using the step motor, the DSP controls the build-in mechanical stage to the focus position to finish the auto-focusing.In this design, with the masterly design of sampling window, DSP can sample the imaging data directly, which has saved the common sampling controller and memory, and reduced the development costs.This paper focuses on the auto-focus algorithm. In the research, a method of prejudging the direction of search is used in the searching algorithm, while a new searching strategy based on hill-climbing searching algorithm is presented. With the improved merit function, the searching area is expanded, the rate of searching into local peak is reduced and the success rate of auto-focus is improved.In the field of programming, the software efficiency is greatly improved with the powerful computing ability of the DSP and code optimization.The auto-focus system shows good performance in searching scale, focusing time and focusing precision. The system is running high stability, effective and fully capable of commonly used microscopes auto-focus tasks.