Application Of Holographic Interferometry And Computer Tomography To Full-Field Measurement Of Asymetric Refractive Index Distributions

Dean D. Verhoeven

doi:10.1117/12.950234

31 March 1989 Application Of Holographic Interferometry And Computer Tomography To Full-Field Measurement Of Asymetric Refractive Index Distributions

Dean D. Verhoeven

Author Affiliations +

Proceedings Volume 1026, Holography Techniques and Applications; (1989) https://doi.org/10.1117/12.950234
Event: 1988 International Congress on Optical Science and Engineering, 1988, Hamburg, Germany

Abstract

Multi-directional holographic interferometry, combined with the techniques of computed tomography, can provide a powerful tool for the study of transparent media. With such a system, one can measure the three-dimensional distribution of index of refraction in a transparent medium at an instant in time. In many situations, the index of refraction can be uniquely related to other variables of interest, for example temperature or species concentration in a gas flow. This paper reports on the development of such a holography-based computed tomography system for laboratory measurements, with emphasis on the accuracy attainable with such a system. The design of the homographic measurement system is presented, and the data-taking procedure described. Data reduction using two Hartley transform-based computed tomography algorithms is described. The first of these is similar to the single-step Fourier extrapol-ation technique developed by Sweeny and Vest. The second is an iterative technique based on Gerchberg's spectral extrapolation algorithm. The performance of these algorithms is compared using numerical "phantom" temperature distributions. Preliminary measurements of the temperature distribution in an asymetric convective hot air flow were made using the holographic system. These are compared to measurements made in the same flow using an array of fast-response thermocouples.

Citation Download Citation

Dean D. Verhoeven "Application Of Holographic Interferometry And Computer Tomography To Full-Field Measurement Of Asymetric Refractive Index Distributions", Proc. SPIE 1026, Holography Techniques and Applications, (31 March 1989); https://doi.org/10.1117/12.950234

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