ELECTRONIC SPECKLE PATTERN SHEARING INTERFEROMETER USING HOLOGRAPHIC GRATINGS

We propose two methods to perform shearing in electronic speckle patte rn shearing interferometry (ESPSI). These new methods of shearing make the setup compact and easy to align. The first system we propose cons ists of two parts: (1) the object is imaged onto an intermediate groun d glass and (2) the image on the ground glass is in turn imaged onto t he photosensor of a CCD camera. A holographic grating placed in front of the ground glass screen is used to shear the two images and to intr oduce phase stepping. The separation between the grating and tile grou nd glass plate is used to control shearing. In the second method, two identical holographic gratings separated by a distance introduce shear ing and the distance between two gratings can be used to control the s ize of shearing. Phase shifts to be employed for phase measurements ar e introduced by displacing the grating. (C) 1997 Society of Photo-Opti cal instrumentation Engineers.