| Quartz glass is widely used in high-energy lasers,special light sources,semiconductors and other industries due to its excellent physical properties.The subsurface damage introduced in the lapping process of quartz glass affects the removal amount and processing efficiency of the successive step.The rapid and accurate detection of the subsurface damage introduced in the lapping process can guide the process optimization and improve the process quality and efficiency of quartz glass.However,there is a lack of rapid and accurate non-destructive detection methods with regards to lapped quartz glass.In this dissertation,a polarized laser confocal nondestructive detection(PLCND)method was proposed to detect the subsurface damage of lapped quartz glass.The testing system was built.Based on this detection system,the subsurface damage distribution map was obtained by image processing.The mathematical relationship between surface roughness and subsurface damage depth was established to guide the PLCND system.The main research contents and conclusions are as follows:(1)In view of the rough surface of quartz glass after lapping,this paper analyzes the advantages and disadvantages of the existing detection methods.The polarized laser scattering method can detect the subsurface damage of the rough surface,and the confocal scattering method can acquire high resolution.Combining the advantages of these two detection methods,PLCND method was proposed.The detection system was designed.The detection principle was introduced.Based on the optical transfer function,the relationship between the detection resolution,the optical wavelength and the numerical aperture of the objective was obtained,which can provide reference for the subsequent system construction.(2)According to the basic principle of the PLCND system and the optical properties of the quartz glass,the key components of the system were selected and assembled.The radial resolution of the system is 0.57 μm,and the axial resolution is 0.70 μm.The software of polarized laser confocal system was designed by Lab VIEW,and the functions of automatic scanning and data acquisition were realized.The subsurface damage distribution map was obtained by image processing.Combined with the theory of indentation fracture mechanics,the prediction model of subsurface damage depth of lapped quartz glass was established,which indicates that the prediction model can guide the scanning depth of PLCND system.(3)Four groups of quartz glass were lapped with four different abrasives,and the surface roughness ranged from Ra0.46 μm to Ra1.22 μm.Different subsurface damage was prefabricated.The samples are measured by PLCND and cross-sectional microscopy destructive methods,respectively,and the results are compared.The results show that the relative error of subsurface damage depth is less than 5%,and the configuration of subsurface crack is consistent,which verifies the feasibility of PLCND method.Finally,the PLCND system was used to scan the 3D subsurface damage of lapped quartz glass,and the 3D scanning results were reconstructed by using MIMICS software.The 3D subsurface damage of lapped quartz glass with high resolution is obtained. |
