Study On The Simultaneous Phase-shifting Anti-Vibrational Interferometry

Simultaneous phase-shifting interferometer is vibration insensitive, because more than three interferograms are captured simultaneously and affected samely by the environmental vibration. Three simultaneous phase-shifting interfrometry schemes are investigated in this dissertation, including 1) beam-spliting by prism and phase-shifting by polarizers, 2) beam-spliting by prism and phase-shifting by waveplate and 3) beam-spliting by grating and phase-shifting by polarizers. The mathematical models and the Jones Matrix-based phase-shifting arithmetics are proposed. The experimental system is designed with grating beam-spliter and polarizers phase-shifter, which is based on the Twywan-Green polarized phase-shifting interferometer. A CCD camera with adjustive-electric-shutter is employed to capture all phase-shifting interferograms instantaneously in vibrational circumstances so that the phase-shifting anti-vibrational interferometry is realized.The pivotal technologies of the simultaneous phase-shifting interferometry are studied in this dissertation, including the intensity matching and the spatial coincidence of interferograms. The diffractive efficiency model of the 2-dimensional grating is achieved and the (±1,±1) ranks of the grating are chosen as the beam splitting cells so that the intensity matching problem is solved. The initial phase differences of the horizontal spatial corresponding points on the four divided independent interferograms are analyzed to solve the spatial coincidences problem. A large aperture polarizer is put in front of the CCD camera and rotated to confirm the precision of the polarizer array according to the positions of light extinction.Error sources are analyzed in three aspects, the interfermtric system, the beam-splitting system and the phase-shifting system. It is indicated that the azimuthal error of the polarizers array and the spatial coincidence error of interferograms are the main errors of this system while the solutions to all the errors are put forward. In order to study the vibration effect of the environment with different frenquencies, a PZT vibration source is designed and used to make a quantitative analysis for the anti-vibration performance of the experimental system. The results show that the testing repeatability is less than 0.02λwhile the amplitude-frequency product of the vibration is under 100λHz.To validate the precision and to test the performance of this system, the measurement result of a microscope object lens by our system is compared with that by the Zygo interferometer, and the results coincide well. Moreover, a low-reflectivity surface and a flow are also tested on this experimental system. A scheme of dynamic measuring for the phase retardation distribution of quarter- waveplate is carried out based on the simultaneous phase-shifting technique in this dissertation. The arithmetic is given by means of both Miller Matrix and Jones Matrix, and an actual quarter- waveplate is measured whose normal wavelength is 632.8nm. Fine retardation uniformity is shown on the results because almost 75% retardation errors are within 5nm.