ADDITIVE-SUBTRACTIVE 2-WAVELENGTH ESPI CONTOURING BY USING A SYNTHETIC WAVELENGTH PHASE-SHIFT

The addition correlation of two speckle fields by simultaneous illumin ation at different wavelengths is used for object contouring in a Twym an-Green-type interferometer. Fringe visibility is enhanced when the s tochastic speckle background intensity obtained from a reference plane modulation is subtracted. We calculate the contour phase map by using a phase-shift algorithm in the synthetic wavelength. A comparison wit h a sequential illumination, phase difference method based on a laser wavelength phase shift is given. The test setup does not need to be st able on an interferometric scale, and therefore a method is provided t hat lends itself to applications in noisy environments. (C) 1998 Optic al Society of America.