Improved zone-plate interferometer for measuring aspheric surface

The creation of referring wavefronts for the measuring aspheric surface is a challenge in the field of optical measurement at present. The improved zone-plate interferometer is proposed to solve the problem in this paper. The principle of zone plate interferometer is discussed and the theory modal is analyzed. The structure of the interferometer is designed and slightly different from that of the Smartt zone plate interferometers. A new computer generated hologram (CGH) zoneplate is designed and manufactured, which acts as null optical element in the interferometer. The corresponding experimental system is built and the interferograms are processed with fast Fourier transform (FFT), phase unwrapping and surface fitting algorithm. Theoretical analysis and experiment results indicate it achieves worthy measurement precision.