1 May 1994 Three-dimensional shape measurement using images reconstructed by the computer from a hologram
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Abstract
Laser holographic interferometry has been developed to provide a direct optical transonic flow diagnostic tool. It is often convenient, due to the needs of passage instrumentation and blade fixtures, to restrict optical access to one side of the test facility. To overcome this limitation a reflective holographic system has been devised which uses one of the internal tunnel walls as a mirror surface. However, due to the movement of the facility, spurious rigid body vibration information is added to the transonic flow data. A numerical method has been developed by Warwick University and demonstrated on the Laval nozzle flow facility at EPFL which uses a digital fast Fourier transform algorithm to remove the superimposed background information. A further method known as phase unwrapping is used to extract quantitative numerical data from the interferometrically formed images automatically. A complication to the experiment was created by the non-linear deflection of glass window between the two holographic exposures. The deflection was determined experimentally to be of a parabolic nature and has been successfully removed. This was achieved by post processing the unwrapped fringe data.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yoshinori Kajiki, Hiroaki Ueda, Kenji Taima, Hideki Okamoto, and Eiji Shimizu "Three-dimensional shape measurement using images reconstructed by the computer from a hologram", Proc. SPIE 2176, Practical Holography VIII, (1 May 1994); doi: 10.1117/12.172643; https://doi.org/10.1117/12.172643
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