REMOTE SENSING OF SURFACE STRUCTURES

A.W. Koch, P. Evanschitzky, M. Jakobi

Abstract

The current technical set-up of speckle interferometry is based on temporal phase-shifting with a single CCD camera, which requires a vibrationisolated environment. In order to apply the phase-shifting technique to an industrial environment, without any vibration isolation, four phase-shifted speckle images are simultaneously acquired by means of four cameras. In order to achieve this aim we use four parallel speckle interferometers. The appropriate phase differences between the beams are realized by variable path differences employing movable prisms. This new laboratory set-up demonstrates the feasibility and the applicability of long-range surface structure, surface deformation and surface profile measurements. The change of surface structure, caused e. g. by erosion, influences the fringe contrast of the interference fringes and their visibility of the phase-shifting method. An additional modelling of the quadruple speckle interferometer using a ray tracing simulation program demonstrates the dependence of the fringe contrast on surface structure modifications in the nanometer scale. The ray tracing method takes into account the effects of polarization, diffraction and interference. Measurement results verify the detectability of eroded surface areas.

Keywords

speckle interferometry, spatial phase shifting, multichannel set-up, simulation, ray tracing, erosion

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IMEKO-WC-2000-TC2-P042.pdf

DOI

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IMEKO TC

TC2 - Photonics

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