title: Two-wavelength Talbot effect and its application for three-dimensional step-height measurement.
abstract: The phenomenon of Talbot self-image shift by changing the wavelength of the illuminating light is described and demonstrated experimentally. A periodic grating is illuminated by light with wavelengths lambda1 and lambda2 generated by two lasers, and the Talbot self-images are recorded along the longitudinal direction at individual wavelengths. The Talbot self-image shift due to the change in the wavelength of light is implemented for the measurement of the three-dimensional step height of a large discontinuous object without any phase ambiguity problem. Fourier-transform fringe analysis was used to determine the maximum contrast of the high-visibility bands for the measurement of the step height of the object. The main advantages of the proposed system are nonmechanical scanning, high stability because of its common path geometry, compactness, and a wide range of measurement as compared to interferometric three- dimensional profilers.
authors.affiliation: Laser Applications and Holography Laboratory, Instrument Design Development centre, Indian Institute of Technology, Dehli, India. dsmehta@iddc.iitd.ernet.in
authors.forename: Dalip Singh
authors.initials: DS
authors.lastname: Mehta
authors.forename: Satish Kumar
authors.initials: SK
authors.lastname: Dubey
authors.forename: Chandra
authors.initials: C
authors.lastname: Shakher
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Takeda