The addition correlation of two speckle fields by simultaneous illumination at different wavelengths is used for object contouring in a Twyman–Green-type interferometer. Fringe visibility is enhanced when the stochastic 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 with a sequential illumination, phase difference method based on a laser wavelength phase shift is given. The test setup does not need to be stable on an interferometric scale, and therefore a method is provided that lends itself to applications in noisy environments.
© 1998 Optical Society of America
Original Manuscript: August 28, 1997
Published: May 1, 1998
Erwin Hack, Bruno Frei, Ralf Kästle, and Urs Sennhauser, "Additive–subtractive two-wavelength ESPI contouring by using a synthetic wavelength phase shift," Appl. Opt. 37, 2591-2597 (1998)