Abstract
Large surface movements can be conveniently measured with holographic interferometry by using a moiré technique. A comparison grid is produced at the test surface by projecting onto it parallel interference fringes. Reconstruction of the surface shows a moiré fringe pattern formed by the product of the holographically generated fringes and the projected grid. If the spatial frequency of the grid is within a certain range, the moiré fringes are appreciably coarser than either the holographic fringes or the grid. A measurement of the moiré fringe spacing and orientation allows determination of the form of the holographic fringes and, hence, surface deformations can be calculated. This method can be used to extend the range of holographic interferometry by at least an order of magnitude.
© 1971 Optical Society of America
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