Hologram Interferometry and Laser Speckle Methods: Further Applications
The wavefront reflected from a surface may be stored in a holo gram and subsequently reconstructed to take part in optical interference with any other wavefront. In applications where surface deformation is to be measured, the two wavefronts, although complex, are very similar, and the concept of homologous rays can be used. If two different surfaces are to be compared, however, the wave-fronts scattered from each will in general be too dissimilar in detail to yield an interference pattern showing the mean difference in shape. This difficulty can be overcome to some extent by illuminating the surfaces at a high angle of incidence, when an increasing proportion of the light will be scattered specularly. The nearly smooth waves so generated can then be compared interferometric-ally. The high angle of incidence will of course decrease the sensitivity of measurement.
KeywordsSpeckle Pattern Double Exposure Contour Spacing Surface Profile Height Speckle Pattern Correlation
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