1 January 1992 Study of ultrafine displacements by microdifferential holography
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Abstract
We describe a multiplexed form of phase-step interferometry suitable for measuring and mapping deformations at the nanometric and subnanometric level. Differential holograms of an object under stress are obtained by twin exposures sandwiched about a phase shift of (pi) (1 + 2(delta) ) or (pi) (1 - 2(delta) ) radians in the reference wave. Two reference waves are employed, and a conjugate pair of such holograms is recorded simultaneously, with (delta) < < 1, on high-resolution medium. The differential holograms of the pair are read individually. The interferograms reconstructed therefrom, once placed into accurate registration, are electronically reconstituted into an image in which small displacements are mapped linearly into intensity. An improved registration method used in the present work permits us to map displacements smaller than 0.4 nanometer within the optically sparse specimens that we use for calibration.
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Mark Sharnoff, Mark Sharnoff, Hungyi Lin, Hungyi Lin, } "Study of ultrafine displacements by microdifferential holography", Proc. SPIE 1553, Laser Interferometry IV: Computer-Aided Interferometry, (1 January 1992); doi: 10.1117/12.135309; https://doi.org/10.1117/12.135309
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