The addition correlation of two speckle fields by simultaneousillumination at different wavelengths is used for object contouring ina Twyman–Green-type interferometer. Fringe visibility is enhancedwhen the stochastic speckle background intensity obtained from areference plane modulation is subtracted. We calculate the contourphase map by using a phase-shift algorithm in the syntheticwavelength. A comparison with a sequential illumination, phasedifference method based on a laser wavelength phase shift isgiven. The test setup does not need to be stable on aninterferometric scale, and therefore a method is provided that lendsitself to applications in noisy environments.
© 1998 Optical Society of America
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)