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19 December 1986 Moire Interferometry With Chromatic 1Ight
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Abstract
Experimental observations and measurements are essential sources of information for the correct development of mathematical models of real materials. Moire interferometry offers high sensitivity in full-field measurements of the in-plane displacements on the surface of a specimen. Although it is a powerful method in experimental stress analysis, it has some shortcomings. One is that existing systems require highly coherent light. The only sufficient source of light for this application is a long cavity laser, which is relatively expensive and at best quite cumbersome. Another shortcoming is that measurements must be performed in a vibration-free environment, such as that found on a holographic table. These requirements limit the use of existing moire interferometers to a holographic laboratory. In this publication a modified concept of compensation is developed that permits the use of a chromatic source of light in a compact moire system. The compensator provides order in the angles of incident light for every separate wavelength, so that the virtual reference gratings created by each wavelength in a continuous spectrum are identical in frequency and spatial position. The result is a virtual reference grating that behaves exactly like one created in coherent light. With this development the use of a laser diode, which is a noncoherent light source of tiny dimensions, becomes practical. The special configuration of the optics that create the virtual grating allows its synchronization with the specimen grating and leads to the design of an interferometer that is relatively insensitive to the vibrations found in a mechanical testing laboratory. Sensitivity to relative motion is analyzed theoretically. This development provides the opportunity to apply moire interferometry to solid mechanics problems that cannot be studied in an optics laboratory. Experimental verification of the optical concepts is provided.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robert Czarnek "Moire Interferometry With Chromatic 1Ight", Proc. SPIE 0679, Current Developments in Optical Engineering and Diffraction Phenomena, (19 December 1986); https://doi.org/10.1117/12.939581
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