Simultaneous Phase-Shifting Interferometry Based on high-speed CCD

摘要

A new simultaneous phase-shifting measuring method based on Twyman-Green polarization phase- shifting technique is presented. In the corresponding set-up, a 2-dimentional grating is applied. By the grating, 4 diffracted beams of (±1, ±1) orders are formed for the same diffracting efficiency. Each is let to pass one of four polarizing plates respectively, polarization directions of which differ in turn by 45°. So four interferograms with 90° phase-shifting interval are frozen simultaneously by a high-speed CCD, which has short exposure of 1/10000 s. Moreover, by the use of 4-bucket algorithm, a profile of the test surface is thus derived. Meantime, the system is deposited on a vibration-isolate flat, and the structure of an ordinary piezoelectric transducer (PZT), with a time response above 1000 Hz at amplitude of λ/2, is used to simulate an epicenter, the frequency of which varying from 10 Hz to 200 Hz. In addition, the experimental results reveal that the advanced system has a high testing precision and testing repeatability in the vibrational environment whose amplitude- frequency product is less than 100 Wave-Hertz. Therefore, the proposed system has enough endurance to the vibration during on-line optical testing.