title: Phase-stepped speckle shearing interferometer by source wavelength modulation.
abstract: Phase stepping by wavelength modulation of the optical source is demonstrated in a path-length unbalanced shearing interferometer. A magnification difference, which accompanies the path-length imbalance in the interferometer, introduces an unwanted radial shear, which is shown to be compensated by inclusion of a block of high-refractive-index material in the longer interferometer arm. The block also increases the phase shift obtained for a given wavelength change. The phase-stepping technique is demonstrated with a three-step algorithm to measure out-of-plane strain on a f lat metal plate.
authors.forename: J R
authors.initials: JR
authors.lastname: Huang
authors.forename: H D
authors.initials: HD
authors.lastname: Ford
authors.forename: R P
authors.initials: RP
authors.lastname: Tatam