Research On The Detection Technology Of Large-aperture Optical Element Body Defects

The strict requirements have been proposed for optics in modern optical engineering.The large scale optical components used to ICF are required for precise surface shape,ultra-smooth,few defects.The internal defects of the large optics in high power laser fecility,can not only modulate the amplitude or phase of the incident light to reduce the beam quality and load capacity,but result in the damage in the optical components and its downstream components.To guarantee the stable running of high power laser facility,the testing ability for the large optics are needed to be established urgently.To measure the amplitude defect of large optical component a testing method based two kind of technique is adopted by integrating their advantages.A qualitative method and a quantitative technique are proposed to form a compound testing method.First of all,the defect the dark field scattering imaging technique recognizing and locating defect is used.The optical component is illuminated in the side direction by a ribbon laser,and the imaging module is adopted to scan the optical component along its light pass surface to recognize and locate defects;To increase the accuracy of recognition,a method to exclude mirror image is designed.Secondly,a light microscopy is adopted along light pass surface to extract the outline of the known defects.A LED white light source is used to illuminate the measured element perpendicular the surface,and the defects in the measured element are micro imaged.An auto-focusing algorithm based image resolution evaluation is adopted to guarantee the defect is focused when imaged;An algorithm about extracting the outline of the internal defect is designed to represent the characteristic of these defect.To verify the validity of the proposed method,a system testing the internal amplitude defect of large scale optical element is developed.According to the testing need,the technical indicators are designed by means of decomposed.The key modules including the light source,the image acquisition and control and precise translation agencies are designed.In order to increase the detection efficiency,the scanning path and the illuminating aperture are optimal designed.These verification experiments for recognition ability,the extraction precision and efficiency promotion are performed.The results indicate that the recognition ability of the developed system is superior to human vision,and the location deviation is not more than 1.3mm;Meanwhile,the extracted error is not larger than 7.2%of the results from microscope.The largest of the detection efficiency are 51 times than that before the promotion method used when an element with the scanning aperture of400mm×400mm × 50mm are tested.The experimental results verify that the method proposed can be adopted to recognize and extract the amplitude defect,and the developed system can be used to engineering inspection for the internal amplitude defect of the large optics.