Research On Non-destructive Testing Methods For Optical Materials Based On Laser Diffraction Measurement Technology

In the field of industry,we often need to detect the surface or internal defects of the material under the premise of destroying or damaging the material to be tested,which is very important for the material to work normally in the high temperature,high pressure,high load and high speed condition.We refer to this technique as nondestructive testing.With the rapid development of modern industry and science and technology,nondestructive testing technology is playing a more and more important role in improving productivity and reducing production cost.With the development of laser technology,it is more and more widely used in nondestructive testing,and has gradually formed a series of new nondestructive testing technology,such as laser ultrasonic,laser holography,laser speckle,laser diffraction and so on.In this paper,a nondestructive testing method of mirror defects is designed for the nondestructive testing of sapphire,which is widely used in civilian and military aviation fields.In this paper,laser ultrasonic,laser holography,laser speckle and laser diffraction are analyzed,and the principle,method,characteristics,application and development of these four detection techniques are summarized.Based on comparing and analyzing the advantages of laser diffraction detection technique,a method for establishing mirror defects detection system with laser is proposed.On the basis of the diffraction theory of light,a simulation method for simulating the diffraction light of laser diffraction is proposed,and a simulation program based on the Kirchhoff diffraction algorithm is compiled.Based on the simulation and calculation,by adjusting the distance between mirror defects and detected screen,the rule of change is founded according to the simulation result of diffraction field distribution,and then the stability of the optical field distribution on the equiphase surface is confirmed.Then,by analyzing the diffraction field distribution under the condition of different size and shape of defects,the rule of change is found,and the corresponding relationship between mirror defects and the diffraction field theory is established.In this paper,based on the theory of Kirchhoff diffraction,the corresponding defect recurrence diffraction field distribution characteristic under the condition of different size and shape defects is obtained by the inverse algorithm.Through the analysis and comparison,it is found that the diffraction field distribution of defect recurrence has a good one-to-one correspondence with the initial defect light field.So the one-to-one correspondence between diffraction field intensity and defect size and shape is established.The one-to-one correspondence is the evaluation criterion in the actual detection.On the basis of the above research results,a preliminary test device is designed and the experimental data are obtained.