Calibration of single optical wedge compensation test system error by computer generation hologram

As a testing method for large convex aspheric surface, the single optical wedge compensation test has good applicability, robustness and flexibility. However, various errors are coupled with one another during the test process and these errors are difficult to decouple. This affects the accuracy and reliability of the tests. To address this, a method is developed to calibrate the system error of single optical wedge test paths using a Computer Generation Hologram (CGH). We first analysed the source of system error in the optical path of a single optical wedge compensation test as well as the feasibility of using CGH for the calibration of an optical wedge compensation test system. In combination with engineering examples, a CGH was designed for optical wedge compensators with a diameter of 150 mm. Based on the analysis results, the calibration accuracy of the CGH was 1.98 nm RMS, and after calibration the test accuracy of single wedge compensation was 3.43 nm RMS, thereby meeting the high-precision test requirements of large convex aspheric mirrors. This shows that CGH can accurately calibrate the pose of single optical wedge compensators and the test system errors of optical paths. Thus we address the problems affecting error decoupling in test optical paths, and improve the accuracy and reliability of the single optical wedge compensation method. Meanwhile, using CGH calibration, the system errors of the test optical paths, Tap#2 and Tap#3, were 0.023 and 0.011 lambda RMS, respectively.

Automated summary

This article introduces a method of using Computer Generation Hologram (CGH) to calibrate system errors in a single optical wedge test path. By analyzing the source of system error and the calibration accuracy of CGH, it is demonstrated that CGH can effectively improve the testing accuracy and reliability, addressing the issue of error coupling during the test process.