Research On Testing Method For The High Precision Synthetic Wavefront Coding Unit

The synthetic wavefront coding unit(synthetic phase mask plate) is a kind of aspheric surface with non-rotationally symmetric, which integrated with hyperboloid and cubic surface has phase encoding function and optical focus function. Because of its different focal power of each direction, the unit can correct some defects of the traditional imaging system. A significant advantage has gradually aroused concern, and has been applied in the simulation of some optical systems. The application of synthetic wavefront coding unit has been limited by optical manufacture and testing technology, because of its particularity of surface shape. Although the optical manufacture and testing technology developed rapidly, the method of manufacture and testing in China is still not mature, and as a whole, it is not able to satisfy the application requirement timely. So in this paper, the main work is to seek a method which can test the synthetic wavefront coding unit accurately.In this paper, based on the surface-shape particularity of the synthetic wavefront coding unit, the computed graphic holograph(CGH) testing method as diffraction compensator is adopted to test the synthetic wavefront coding unit with higher precision. In this paper, the main contributions are as follows:1. Based on the analysis of the surface shape of the wavefront coding unit, four detection schemes are proposed. Through analysis and comparison of the testing principle and performance of schemes, the computed graphic holograph(CGH) testing method is adopted to test the synthetic wavefront coding unit, which will not damage the tested mirror and has high measurement precision and strong practicability.2. The general design idea of the system simulation of testing the synthetic wavefront coding unit via the computed graphic holograph is analyzed. On the basis of the system optimization, performance and parameter of each optical element is determined. Then, the performance and parameter of the testing system are evaluated by using error theory.3. The method to obtain the position of etching stripes of the CGH according to its phase function is discussed. And considering the process, the integrated CGH is fabricated via the laser direct writing technology.4. The experimental platform is built with Zygo interferometer and the CGH, and the testing result of tested mirror is obtained by experiment. Then, the testing result and the measurement error introduced in all aspects are analyzed in detail. Finally, the testing system design of the wavefront coding imaging technology is given via the computed graphic holograph.