Measuring correlation between speckle patterns reflected from rough surfaces at different wavelengths by adaptive photo-EMF detector

Serguei I. Stepanov; Marcos Plata

doi:10.1117/12.446728

23 October 2001 Measuring correlation between speckle patterns reflected from rough surfaces at different wavelengths by adaptive photo-EMF detector

Serguei I. Stepanov, Marcos Plata

Author Affiliations +

Proceedings Volume 4447, Surface Scattering and Diffraction for Advanced Metrology; (2001) https://doi.org/10.1117/12.446728
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

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.

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Serguei I. Stepanov and Marcos Plata "Measuring correlation between speckle patterns reflected from rough surfaces at different wavelengths by adaptive photo-EMF detector", Proc. SPIE 4447, Surface Scattering and Diffraction for Advanced Metrology, (23 October 2001); https://doi.org/10.1117/12.446728

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