Fiber Point Diffraction Interferometer for Measuring SphericalSurface

摘要

An advanced fiber point diffraction interferometer (FPDI) for measuring spherical surface has been developed. It is designed for measuring EUV spherical mirrors with high precision. The quality of the diffraction wavefront, which acts as the referenced wave in the FPDI, is crucial for the measurement accuracy. To estimate the accuracy of FPDI, the theory model for an optical fiber point diffraction source is presented and then numerical calculation is used for analysis. Several key techniques are proposed and analyzed, such as design of short coherence length laser source and interference image processing. The laboratory apparatus has been put up to measure spherical surface in experiment. The results show that the interferometer has achieved worthy measurement precision and has great development potential.