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Proceedings Paper

Measuring correlation between speckle patterns reflected from rough surfaces at different wavelengths by adaptive photo-EMF detector
Author(s): Serguei I. Stepanov; Marcos Plata
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Paper Abstract

Adaptive photodetectors, based on non-steady-state photo-EMF, are suitable both for detection of fast phase modulation in one of the beams forming regular interference fringes and of fast transverse displacement of speckle patterns in a reference-less configuration. In particular, they were used for detection of lateral displacements of rough surfaces, including those induced by nanosecond laser pulses (laser ultrasonic). In combination with light sources of low temporal coherence (i.e. superluminiscent diodes) these detectors can be used for micron resolution profilometry of rough surfaces. In this paper we propose and demonstrate utilization of strong (quadratic) dependence of the photo-EMF signal on contrast of the detected light pattern for simple and fast evaluation of a correlation degree between speckle patterns reflected from the same rough surface at different wavelengths. Experimental results obtained with the GaAs photo-EMF detector and two different lines of a cw Ar-ion laser for transmittance and reflectance configuration (with ground glass and metal plates used as light scattering objects) are presented.

Paper Details

Date Published: 23 October 2001
PDF: 8 pages
Proc. SPIE 4447, Surface Scattering and Diffraction for Advanced Metrology, (23 October 2001); doi: 10.1117/12.446728
Show Author Affiliations
Serguei I. Stepanov, Instituto Nacional de Astrofisica Optica y Electronica (Mexico)
Marcos Plata, Instituto Nacional de Astrofisica Optica y Electronica (Mexico)


Published in SPIE Proceedings Vol. 4447:
Surface Scattering and Diffraction for Advanced Metrology
Zu-Han Gu; Alexei A. Maradudin, Editor(s)

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