A multiplicative analogical moire phase-shifting Twyman-Green technique for Nd : YAG rod wavefront distortion measurement

Nd:YAG rod wavefront distortion has been quantified in a Twyman-Green inter ferometer which employs the multiplicative analogical moire phase-shifting method for demodulation. The measuring procedure is based on the superimpos ition of a transmission grating located outside the interferometric module with a phase modulated high-frequency Twyman-Green spatial carrier. Later, a set of fringe patterns, provided by low-pass filtering of the phase-shift ed multiplicative moire patterns obtained, is combined in a generic phase-s hifting algorithm (GPSA). The interesting test information is achieved once the previous procedure has been carried out with and without the transpare nt object located in the measuring area. The wavefront distortion (WFD) is calculated by the subtraction of these results provided by the GPSA, or dir ectly if a differential phase-shifting algorithm (DPSA) is employed. The WF D obtained is in accordance with characteristics of the test object. The co mparison of the results obtained with both families of algorithms provides information about the sensitivities to error sources of the DPSA employed. A first approximation to the analysis of significant error sources of DPSAs is presented.