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° and 50° would be suitable for a simulation test. Testing accuracy is ensured when the error of the Ritchey angle is controlled within ±1°. 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°. The three Ritchey angles chosen for the experiment are separated into two groups. The residual error between ZYGO and the group of 24.8° and 40.3° is 0.0013 wavelength (λ=632.8 nm). The experimental results confirm that this R-C method is effective and accurate.