Calibration Design And Experimental Research Of Aspheric Measurement System Based On Angle Scanning

Aspheric surface,as the name implies,is a surface deviated from the sphere surface.Compared with spherical mirrors,the radius of curvature of aspheric mirror is not unique,and the surface design is more flexible.Thus aspheric surface has more optical advantages.What's more,aspheric optical elements are important for improving imaging quality,correcting aberrations,reducing weight,improving optical properties,simplifying structure and improving system resolution.With the development of optical device processing technology,it is possible to manufacture large diameter aspheric surface of high precision.Aspheric surface is more and more widely used in aerospace,aviation,shipping,photography,medicine and any other fields.As known to us all,existence originates from measurement.As a result,detection methods and equipment suitable for aspheric manufacturing technology are essential for aspheric applications.The lack of high precision and universal testing instruments restrict the design,manufacture and application of aspheric surface.Interferometric measurements can achieve the desired detection accuracy for aspherical surface with small-diameter.But it is difficult to achieve when it comes to large aspheric surface.High precision measurement of aspheric optical mirrors with large diameter can be achieved by contact measurement but will form scratches on the lens surface.Therefore,the study of large diameter aspheric surface detection method is of great practical significance to improve the observation,remote sensing and early warning level of China.In this paper,the precision design and distribution of the large aspheric high precision measurement system with angle scanning method are presented.Measurement system calibration and compensation is completed.Finally,experiments are carried out to verify the conception by measuring the reflective paraboloid with diameter 50 mm,vertex curvature radius 400 mm.The experimental results show that the surface accuracy reaches PV value of ?/10.Which is consistent with the theoretical analysis accuracy level of the measurement system.Mainly focused on the following aspects:1.Firstly,the sensitive factors of each module of the system are analyzed,which have great influence on two-dimensional curve and three-dimensional surface measurement.Further more,the measurement uncertainty transfer model is done.According to the structure and measurement flow of the measurement system,the precision design and distribution of each module are carried out.2.In order to achieve high-precision measurement of large aspheric surface,the main module accuracy is supposed to reach a certain level firstly.Therefore,calibration and compensation are carried out for scanning motion module(linear guide rail and cosine table)and angle acquisition module(autocollimator).3.Theory must be verified by experiments.Finally,the experimental measurement of aspheric surface is carried out.After obtaining the original measurement data,the idea of combining all the two-dimensional measurement curves in the space cylinder coordinate system is proposed.Then utilize MATLAB powerful curve fitting toolbox to complete a large number of spatial point cloud fitting operations.4.Programming a data acquisition program by combining MATLAB and C + + language.In addition,the human-computer interaction interface is designed by MFC.Theoretical simulations and experimental results on practical aspheric surfaces demonstrate the feasibility and accuracy of the models and program.