Precision Characteristics Of Surface Defects And Optical Microscopic Scattering Imaging System

The detection of defects is one of important detection aspects of precise elements' quality. Defects on optical surfaces can cause scattering and result in damage in elements even in the system. So it's becoming more and more important to detect the defects in optical manufacture and application.According to the detecting requirement of large aperture elements, a new measurement of defects is advanced. Based on it, a new detecting system for defects which is named optical microscopic scattering image-forming system has been founded. In the detecting system, the scattered lights from surface defects are imaged on CCD camera by the microscope. In the image are bright defects in black background, what is suitable for digital image processing. Defects in random distribution and random shape on optical surface can be detected by reasonable design of illumination system of the detecting system. Large aperture surface of precise elements can be detected by the system using the XY-plane scanning system. The lateral resolution of detecting system is approximately 1 jum, and the image and experimental results are very good.In the paper, about three main matters are discussed. Firstly, the characteristics and harm of defects and are reviewed. Then analyze the actuality of defects and the standard of evaluation for defects. In most time, the detections of defects make use of the scattering of defects. So the scattering of optical surface with defects are discussed, and analyze three main scatterings on surface and their affection on the defects scattering imaging.Secondly, all parts of defects detecting system are introduced and analyzed, including illumination system, microscopic imaging system, scanning system and antitheses and standard system. Illumination system and antitheses and standard system are discussed in detail.Thirdly, using the database of standard defects on standard antitheses boards, the relation of defects' real size and defects' imaging size is analyzed detailedly, and the magnification effect of scattered lights imaging for defects is also discussed.Based on the theory analysis, a real detecting system is founded and a systemic study on defects' measurement has been done in the paper.