Holographic system for non-destructive testing

Claim 1

A holographic system comprising: a source of monochromatic light; beam splitting means for dividing this light into an object beam and a reference beam; first illuminating means, comprising a first mirror, for directing said object beam onto an object; holding means for holding and positioning photosensitive material to receive light which has impinged on said object; second illuminating means for directing said reference beam onto said photosensitive material, and comprising second and third spaced mirrors providing an optical path between said means for dividing said light and said photosensitive material; first positioning means for adjustably positioning said first illuminating means for selectively varying the angle of illumination of said object, and comprising means for moving said first mirror along a line parallel to a reference plane corresponding to the plane of said holder and photosensitive material held therein and for selectively rotating said first mirror about an axis perpendicular to said line; and second positioning means for positioning said second illuminating means for selectively varying the angle of said reference beam on said photosensitive material, and comprising means for selectively moving said second mirror along a line parallel with said reference plane, means for selectively rotating said second mirror about an axis perpendicular to said reference plane, and means for moving said third mirror along a line parallel with said reference plane and for selectively rotating said third mirror about an axis perpendicular to said reference plane; whereby the angles at which said beams reach said object and said photosensitive material may be selectively varied and thus the sensitivity of said system to deformation of a test object be varied and said angles may be made identical and thereby obtain interference fringes with a selected degree of detail on said photosensitive material.