Quasi-Heterodyne Hologram Interferometry

P. Hariharan

doi:10.1117/12.7973542

1 August 1985 Quasi-Heterodyne Hologram Interferometry

P. Hariharan

Author Affiliations +

Optical Engineering, Vol. 24, Issue 4, 244632 (August 1985). https://doi.org/10.1117/12.7973542

Abstract

Wider use of hologram interferometry for quantitative measure-ments has been delayed by the fact that interpolation between the fringe maxima and minima to obtain the optical path difference at a particular point in the field is laborious and inaccurate. A solution to this problem is quasi-hetero-dyne interferometry, which permits rapid and accurate measurements simultaneously at a number of points distributed over the interference pattern. In this technique a television camera is used in conjunction with digital electronics to measure and store the irradiance values at points on a rectangular sampling grid covering the real-time interference fringes. The phase difference between the interfering wavefronts at each point is then calculated from the irradiance values obtained from successive scans of the camera made while the phase of one of the wavefronts is shifted either continuously or in steps. A practical system is described with which values of the optical path difference for 10,000 data points can be obtained with an accuracy of ± A/200 in less than 10 s. The application of quasi-heterodyne hologram interferometry to the measurement of vector displacements and to holographic contouring is discussed.

Citation Download Citation

P. Hariharan "Quasi-Heterodyne Hologram Interferometry," Optical Engineering 24(4), 244632 (1 August 1985). https://doi.org/10.1117/12.7973542

Published: 1 August 1985

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