Research On Multi-parameter Distribution Characterization Technology Of Laser Scattering On High-reflection Mirror Surface

The tiny defects on the surface of high-reflection mirror will cause light scattering and light loss,affect the performance of optical components,and damage the precision optical device system.For example,in the laser gyro,it will cause the laser gyro lockup effect,increase the random walk,and have a huge impact on the linearity and stability of the laser gyro output.Therefore,the article studies the darkfield microscopic scattering imaging system for detecting surface defects of high-reflection mirrors,and combines the integral scattering measuring system to perform multi-parameter characterization of the laser scattering rate of surface defects of high-reflection mirror.This article proposes the design scheme of darkfield microscopic scattering imaging system,the focus is on the different effects of single light source,dual light source and three light source illumination on defect imaging measurement during laser illumination,the light path part realizes beam expansion collimation,microscopic imaging enlargement and elimination of stray light,etc.The relationship between CCD sensitivity,resolution,light source power,spot size,imaging system numerical aperture and mechanical structure realization are studied,and the establishment of the darkfield microscopic scattering imaging system.Finally,the overall system debugging and image acquisition are completed.Under the background of strong noise,based on the principle of related detection technology,the optimized integrated scattering measurement system is used to detect the weak scattered light signal of the surface defects of the high-reflection mirror.In actual detection,When the laser light source is used for illumination,there are blind area in the detection of micrometer-level scratch-shaped defects,but the detection blind area can be reduced by rotating the sample or increasing the number of light sources.The movement of the rotating sample will cause motion positioning errors.The movement of the rotating sample will produce movement positioning errors.The design of the light source as a full-light curtain illumination method with no dead angle within the range of 180° can overcome the detection blind area of a single laser light source illumination without rotating the sample,but it will increase the complexity of the optical path design.The actual darkfield microscopic scattering imaging system can switch between different spot sizes and imaging objective optical paths,and can achieve 1x,2x and 10x microscopic imaging,so as to quickly locate and measure the two-dimensional distribution of defects.The measuring range is 3mm and the resolution is 3μm.According to the two-dimensional distribution of defects,the integral scattering measurement system can be used to further measure the integral scattering rate of the area of interest.The measurement range of integral scattering rate is 0.001%-1%,and the measurement error is 2%times the measured value.The integral scattering measurement system measures the scattering rate of the same defects,combined with the two-dimensional distribution of the high-reflection mirror surface defects,which can be used to indirectly characterize the depth information of defects.