17 January 2011 Four channel holographic infrared optical element
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Proceedings Volume 7747, 16th International School on Quantum Electronics: Laser Physics and Applications; 77470K (2011) https://doi.org/10.1117/12.882082
Event: XVI International School on Quantum Electronics: Laser Physics and Applications, 2010, Nessebar, Bulgaria
Abstract
The paper presents a holographic optical element (HOE) for a phase-stepping digital electronic speckle pattern interferometry with double symmetrical illumination of the object both in vertical and horizontal planes for precision full-field displacement measurement of objects under loading . More specifically, the proposed HOE allows for simultaneous reconstruction of four virtual and parallel to the HOE surface reference planes for off-axis illumination with two pairs of diode lasers emitting at two different wavelengths. In this way we transform a two-beam interferometer into a multiple beam interferometer with four separate channels. The HOE is constructed as a sandwich structure of two reflection (Denisuyk type) holograms of a diffuse metal screen illuminated at 30 degrees to the normal. Each of the holograms comprises two holographic reflection records made successively on a single holographic plate. Recording is performed in the visible part of the spectrum, and through additional chemical treatment the spectral maximum of the developed holograms is shifted into the IR region to achieve correct reconstruction for illumination at 790 nm and 830 nm. Super high resolution silver halide emulsion with resolution over 6000 line/mm is used for recording of holograms. The reconstructed four reference beams interfere with the beam reflected from the object, thus forming four independent optical channels for two laser beams at 790 nm with S and P polarizations, as well as for two S and P polarized beams at 830 nm.
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B. Ivanov, M. Shopova, A. Baldjiev, E. Stoykova, V. Sainov, "Four channel holographic infrared optical element", Proc. SPIE 7747, 16th International School on Quantum Electronics: Laser Physics and Applications, 77470K (17 January 2011); doi: 10.1117/12.882082; https://doi.org/10.1117/12.882082
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