Design Of Auto-focusing Image Processing Algorithm And System For Optical Microscope

Optical microscope has been playing a vital role and widely used in biology,medicine and other fields due to its high precision. If the manual focusing is chosen when using a optical microscope, factitious error will be introduced. And at the same time, the observing will become time-consuming and imprecise. However, the application of auto control in optical microscope offsets the drawbacks of manual mode. In other words, auto control will largely enhance the focusing speed and precision.As a key technology of the modern imaging system, automatic focusing technology has gained widespread popularity in various fields. In recent years, though automatic focusing theory and technology have been rapidly developed, it is not mature enough to give service to the field of optical microscope. Optical microscope that can focus automatically are rarely produce.This paper first introduces the development of automatic focusing technology and states the automatic focusing theory. Benefitting by the automatic focusing work done previously, an optical microscopic automatic focusing system which is based on Brenner algorithm is designed. Singlechip together with control software which is programmed by LabVIEW and circuits which are based on MSP430F5438 are used in this system to complete the focusing. The first step of working process is that images are captured by digital CCD and sent to the PC. Then those images are evaluated by the image evaluation arithmetic and the auto-search arithmetic is used to find the best focusing position. At last, with the communication between PC and single chip through serial port, stepper motor is controlled to drive the microscope objective lens to reach the ideal position finally.In order to reduce the mechanical error, elastic coupling is used to couple the stepper motor and microscope handwheel. To improve the precision, the stepper motor subdivision drive technology is introduced.Based on the analysis of several kinds of image evaluation arithmetic,experiments which focus on observing onion epidermal cells and pine cells aredesigned and carried out in this paper. The results show that the curve of Brenner is sharper and more unimodal than others. This system could finish focusing in one minute under different magnification. The experiments verified that the system could meet the actual working requirements both in hardware design and software design.