Design Of On-machine Measuring System And Study On Evaluation Method Of Surface Defects On High-power Optical Elements

The influence of surface defects on optical elements is mainly characterized by scattering on the condition of highlight irradiation,which will cause some harm,including the energy consumption and the damage of film layer,and this will lead to serious impacts on the performances of imaging system.Therefore,the detection of surface defects is given more and more attention in the process of machining and applications for highlight optical elements.At the present,the devices are mainly used for offline defects detection on small and plane optical elements,and it is very difficult to meet the demand for modern optical systems.According to the requirements of surface quality on highlight optical elements,a detection device for surface defects is established,as well as image processing,identifying and evaluating method in this paper based on the dark-field microscopic imaging method and the motion platform of precision machine tool,and it can realize on-machine measurement for surface defects with micron scale on large and non-plane optical elements.The main contents of this paper are as follows:1)Taking the precision machine tool as motion platform,an on-machine measuring system for defects detection on highlight optical elements is designed by planning,selecting and designing the modules of uniform illuminating system,microscopic imaging system,and image collecting and processing system.These requirements are satisfied,which include the detecting range,the surface shape and the detecting precision.2)By studying the influence of machining errors and the deformation of the devices on the illuminating performances,the security of key structures,and the light intensity of measuring areas,the influence factors of defects detection system are analyzed on the working performances,and the system can meet the requirements on image acquisition and clear imaging of defects.3)The elimination of uneven illumination and the contrast enhancement in measuring images for defects detection are achieved in order to realize noise suppression and binarization,and the image recognition and the output of statistic results are accomplished by the design on processing algorithms.4)On the basis of calibration between imaging size and actual size for surface defects on the on-machine measuring system,the testing experiments and the evaluating analysis for surface defects on optical elements are accomplished with different materials,different diameters and different surface shapes.