Eliminating alignment error and analyzing Ritchey angle accuracy in Ritchey-Common test

To improve the accuracy of the Ritchey-Common (R-C) test, this study proposes a method that utilizes the relation between system pupil and test flat coordinates to obtain a flat surface and integrate the least square method to eliminate the effect of misalignment. A Ritchey angle between 20 degrees and 50 degrees would be suitable for a simulation test. Testing accuracy is ensured when the error of the Ritchey angle is controlled within +/- 1 degrees. To avoid measurement error of the Ritchey angle, the ratio of image size to the pupil plane is used to calculate the value. The accuracy can reach 0.2 degrees. The three Ritchey angles chosen for the experiment are separated into two groups. The residual error between ZYGO and the group of 24.8 degrees and 403 degrees is 0.0013 wavelength (lambda=632.8 nm). The experimental results confirm that this R-C method is effective and accurate. (C) 2013 Elsevier B.V. All rights reserved.