Geometry for contouring by electronic speckle pattern interferometry based on shifting illumination beams

When the method of contouring an object surface by electronic speckle pattern interferometry is based on shifting the illumination beams, the shifted phase of the interference speckle pattern has a new relationship with the depth of the test surface. Therefore the contour interval as well as the fringe sensitivity of this method has new forms. The geometry of such a situation, which differs from that of either the method of two-wavelength contouring or the method of contouring by tilting the test object is presented. The requirements on the experimental conditions for this method are also presented. Experimental results are in agreement with these analyses.