Testing aspheric surfaces with computer-generated holograms : analysis of adjustment and shape errors

Abstract

Various interferometric methods can be used for testing aspheric surfaces with high accuracy. Using a partially compensating lens in a Twyman-Green arrangement together with a computer-generated hologram instead of a null corrector gives great flexibility. For quantitative analysis a high-resolution automatic fringe analysis is necessary. The interferometric arrangement and the setup for the interferogram data acquisition are described along with different algorithms for calculating the wave front data. Tilt and decentering of the aspheric surface and the synthetic hologram as well as the actual aspherical parameters can be derived from the calculated wave front using Zernike polynomials to communicate with a ray tracing program. For small adjustment and shape errors the linearity will hold, leading to fast correction and numerical compensation of their effects on the surface error. The method is verified by several examples. Experimental results agree with the proposed model.