Study Of Dynamic Interferometry Technology And Application

Phase Shifting Interferometry (PSI) is widly used to test optical element and optical system; however, phase shifting interferometer is extremely vibration sensitive as a series of interferograms are captured at different times. A spatial phase shifting dynamic Fizeau-type interferometric system is studied in this paper, which could capture four phase shifting interferograms simultaneously and instantaneously, therefore influence caused by vibration is eliminated.The arithmetic model of dynamic interferometry is deduced based on the principle of polarization interference, and the experimental system is built. The method of using a moudulated semiconductor laser as the light source is proposed. Coherence of the light source in conjunction with a polarization delay-line are used to separate the orthogonally polarized test and reference beam components for interference. Spatial phase-shifting system is realized by a 2D grating and a polarizer group, and four interferograms withπ/2 phase shift between adjacent ones are captured by a single CCD. The wavefront is retrieved by using the 4-bucket algorithm.The calibration method of spatial phase shifting device is researched. A Soleil-Babinet Compensator is used to calibration the actural shifted phase, and the experimental results indicate that the phase shifting errors is less than 1°; The performance of dynamic phase testing is researched. A PZT vibration source is designed and the relationship between visibility and frequency under different exposure time are measured. The testing repeatability of this system is less than1/60λwhile the amplitude-frequency product of the vibration is under 100λHz; Dynamic phase variations are tested; Error analysis shows that the azimuthal error of the polarizers array and the spatial coincidence error of interferograms are the main error sources.To remove the error of interferometer reference flat, a novel method is presented to achieve the absolute flatness measurement based on two plates in the Fizeau interferometer. The equations are derived and experiments are carried out. The experimental result is compared with that of ZYGO's three-flat application, and both coincide quite well. The two surfaces' figure of a parallel plate and its imhomogeneity are measured by the dynamic interferometer bsed on this method. The two-flat method is then extended to calibrate a 600mm aperture Fizeau interferometer.