Microscope Autofocus System Design And Optimization

As a necessary and key technique in modem imaging system, auto-focus is used more and more in many areas, such as daily life, science research, and military affairs. Although, a lot of theories and methods of Auto-focus have been developed quickly recently, the application of Auto-focus is not mature enough, and needs more research. Microscope is applied widely as an optical instrument. However, the auto-focus system applied to microscope is not widespread. In this paper, we designed and optimized an auto-focus system applied to microscope, which based on SCM controlling and CCD analog signals processing. In this system, a multi-feedback bandpass active filter filters analog video signals outputted from CCD firstly. The radio-frequency component in the signals, which represents image definition, is magnified and then is adjusted by integrator. And this is regarded as the focus evaluation of estimate. After A/D transposition, the focusing is droved by actuating mechanism, which is controlled by SCM.First, the present status of auto-focus technique, basic theories and methods has been introduced briefly. Then the theory referred to this system that based on analog signals processing has been analyzed. And the total structure of the system has also been discussed.The thesis contains several chapters about different aspects of the system. And the major content is that some optimized methods have been adopted in the system on hardware and software. About hardware, the choice of the pass band of the Multi-feedback band-pass active filter, the amplification of the shunting signal, the solution of the drift problem between line in video frequency and SCM period, and the optimized drive mode of the motor has been discussed detailed. About software, searching algorithm has been optimized. The focus evaluation function and the choice of the focusing window have also been described. These methods have been proved that they are good to the improvement of the system performance by a series of experiments.At the end of the dissertation, the orientation to improve the performance of theauto-focus system in microscope is also discussed briefly.The target set in the early stage of the project that auto-focus system in microscope has been completed primarily. After optimization, the system can focus automatically more quickly and more accurately, and this system become more suit to produce.