Statistical analysis of surface defects of large-size gratings

During the manufacturing process of gratings, the type and location of defects on the grating surface have a very significant impact on the performance of the grating. Statistical analysis of the types, sources and transmissibility effects of large-size grating surface defects is very important of grating manufacturing. This article collects a large amount of surface defect data accumulated during the grating production process. In the experimental and statistical process, we classified the defects on the surface of the large-size reflection diffraction grating development mask as the research object, and using three methods: manual visual inspection, CCD imaging and metallographic microscope observation to classify the surface defects. After analysis, the defects on the grating surface were finally classified into surface covering defects, embedded defects and substrate scratch defects based on the spatial position of the defects on the sample surface. The physical characteristics of different defects and the classification methods of different types of defects were summarized. Statistics were made on the impact of dust, lint, black and white spots, finger marks and other common defects in the grating manufacturing process on grating manufacturing, as well as the causes and patterns of defects. Experimental results show that the proposed statistical results of grating defects are simple and effective in avoiding defects in the manufacturing process of large-size gratings, and the defect types covered can include most of the defect types produced by grating manufacturing. This statistical result is of great significance to evaluating the quality of grating products and tracing the defects of finished products.