Research On Surface Testing System Based On Deflectometry

Surface testing technology has become the most important factor restricting the development and massive application of various aspheric components and free-form surface components.This dissertation mainly research on the surface testing system based on deflectometry,which provides a contact-free,high dynamic range,full field metrology method with simple system setup in high-precision surface testing,especially in convex surface testing..In addition,this paper effectively analyses and calibrates the off-axis error and geometric error in the testing system,which improves the testing accuracy of the system.The main content of this dissertation include:The great contribution of high-precision surface testing technology to the modern optical testing system is discussed.After a review over the current free-form surface testing methods,the necessity of this research is put forward.From the view of reverse Hartmann test,a ray tracing model is proposed to eliminate the geometry aberration in optical system by analyzing the main geometry errors.Besides,the Zernike polynomial is applied to illustrate the influence of each geometry error,and the necessity of the geometry calibration is explained.A two-step calibration method based on Zernike fitting is proposed,and the feasibility and high accuracy of the calibration method are verified by simulations.The effect of system geometry aberration is effectively eliminated,which provides a powerful guarantee for high-precision freeform surface testing system.A convex surface with a diameter of 50.8 mm is measured in a surface testing system based on deflectometry.At the same time,the two-step calibration method based on Zernike fitting is used in experiment for improving system accuracy.Finally,the system test results are compared with the results measured by ZYGO interferometer and the error is only 0.7 nm(RMS).