Research On Surface Defect Detection And Inversion Technology Of Large Aperture Optical Elements

With the rapid development of optical industry,optical components are more and more widely used in various fields.The optical system composed of them has played an extremely important role in civil,military and scientific research fields.The surface defects of optical elements seriously affect the scattering characteristics of optical elements,which affect the laser damage threshold of the whole optical system,the imaging quality of the optical system,and the stability of the system and other important performance.Therefore,strict requirements of the surface quality inspection of optical elements have been put forward.In this paper,The theory of micro scattering dark field imaging detection technology is studied,the relationship model between surface defects and surface roughness is built,and the three-dimensional information detection of surface defects is realized through this.In order to obtain the three-dimensional information of optical element surface defects,the current research status of optical element surface defects detection and micro scattering dark field imaging detection is described.The micro scattering dark field imaging method and the relationship between surface defects and surface roughness are studied.Firstly,the basic theory of the micro scattering dark field imaging method is studied.The micro scattering dark field imaging detection system is designed according to the requirements of the measured elements,which realize the detection of the two-dimensional information of the surface defects of optical elements.On this basis,the relationship among surface defects,total integrated scattering and surface roughness of optical elements is analyzed,and the model showing the relationship between surface defects and surface roughness is given to detect the depth information of optical elements surface defects.Secondly,the simulation model showing the relationship between surface defects and surface roughness is analyzed to verify the correctness of the model.This part includes simulation work of gaussian random rough surface.According to the type and shape of the surface defect,defects are added on the simulated Gaussian random rough surface to obtain a random rough surface with defects.According to the model showing relationship between the surface roughness and surface defects of optical elements,the depth information of surface defects is obtained.Finally,a measurement system of micro scattering dark field imaging is built.Using this system to detect the standard scratch plate,the scratch width detected by the micro scattering dark field imaging system is basically same as the standard scratch width with the error range from-0.30?m to 2.60 mm and the relative error range from-5.00% to 5.50%.On this basis,the30mm*30mm optical element is selected and its two-dimensional information is measured bythis system.Then,according to the relationship model between surface defect and surface roughness,the depth information of optical element surface defect is obtained.The experimental results show that the depth of the scratches measured by the white light interferometer is basically same as the depth calculated by the roughness with the deviation from 0.58 nm to 2.62 nm.In summary,this dissertation mainly studies the micro scattering dark field imaging technology,the inversion model of surface defect depth,so as to realize the detection of defect three-dimensional information.