| Machine vision systems use image capture devices to convert captured-targets into image signals,then transmit them to dedicated image processing systems,and change them into digital signals according to the distribution of pixels,the brightness, the color and other informations; Image processing systems operat these signals to extract target features,then control the movements of equipments at the scene according to the results of operation.The micro-vision system uses the microscope and the CCD camera as the image capture device. When observating and testing biological samples with a microscope, manual focusing always needs long time and makes some errors affecting the image quality. Thus, automatic control and automatic focusing of the microscope is necessary.The design of the automatic focusing system is based on digital image processing. Use the frame grabber to capture microscopic images of biological samples taken by the CCD camera,then send them to the PC. Evaluate the definition of the image after the choice of windows,image preprocessing and definition evaluation steps.Then use the DSP microcontroller to control the operation of the stepper motor which drives the microscope objective lens up and down movement to complete the automatic focusing.In this paper firstly analyze the theory of optical imaging model, lead to the defocus fuzzy theory establishsing the foundation of the image definition evaluation function. Then design four parts of the automatic focusing system:image acquisition part,image processing part,serial communication part and servo control part.Elaborate the related algorithms and simulation analysis of window selecting, preprocessing, definition evaluation,and extremum searching modules,improve them according to the actual project background.Finally the simulation results and experimental performance show that the improved algorithm of the automatic focusing system can meet the project requirements. |
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