Study Of Contrast Enhancement Technique Based On Oblique Illumination

Microscopic microscope illumination system plays an important role to ensure that system performance,visual observation and photographic effect in a good state.The illumination system mainly comprises collector, condenser, field diaphragm, aperture diaphragm.In order to ensure good illumination uniformity, lighting efficiency and resolution while better enhanced image contrast,dark field technique,oblique lighting technique and phase contrast microscope have already been put into use and development.However we must increase phase contrast sliding panel and dark field sliding panel in the aperture diaphragm surface when we take the above technique,of which the switching process is complex and the operational flexibility is low.This paper mainly study on contrast enhancement techniques based on oblique illumination while giving consideration to both efficiency of lighting and illumination uniformity.First, putting forward the evaluation method of microscopic illumination uniformity and lighting efficiency, and analysis of the relevant theory of Kohler illumination.Then taking several program to test combined with dark field illumination and Rheinberg illumination and the results were analyzed and studied.The paper puts forward the simplified Kohler illumination using LED array for illumination.Using the simplified Kohler illumination to realize dark field and Rheinberg illumination to enhanced image contrast.To avoid errors and mistakes which may caused by the insufficiency of condenser aperture angle happen during the test,we re-optimization and design the condenser.According to the requirement of illumination uniformity, lighting efficiency and lighting aperture angle,we first reasonable design and optimization the condenser with the help of ZEMAX.Then setting the simplified Kohler illumination system up which based on LED array illumination with lighttools and conducting simulation comparison with the original illumination system.Meanwhile using the new illumination system obtained by company manufacture to conducting experimental comparison with the original illumination system and analysis the result.The results show that for bright field illumination, the simulation results and experimental results both show that the new lighting system meets the illumination needs of uniformity although the efficiency have reduced to a certain extent.For dark field illumination,after many experiments and improving lighting facilities,the new system can quickly switching the illumination mode form bright field to dark field by controlling the LED array and significantly improves the contrast of microscope image.Meanwhile as a more efficient method to achieve rheinberg illumination, the new illumination system provides a new way to improve the flexibility of switching between different contrast technology.