ON THE DETERMINATION OF SLOPE BY SHEAROGRAPHY

This paper presents the theory and experimental technique whereby the slope at any point on the surface of an object can be measured. The object under study is first illuminated by a laser beam expanded through an optical fibre and its image recorded on a photographic plate placed at the image plane of an image-shearing camera. A second exposure on the same photographic film is made after the light source is moved slightly in a certain direction. Experimental results for objects of known shapes demonstrate that the local slopes determined from the reconstructed fringe pattern compare well with the actual values.