Use of spatial phase shifting technique in digital speckle pattern interferometry (DSPI) and digital shearography (DS)

Digital speckle pattern interferometry ( DSPI) and digital shearography ( DS) are well known optical tools for qualitative as well as quantitative measurements of displacement components and its derivatives of engineering structures subjected either static or dynamic load. Spatial phase shifting ( SPS) technique is useful for extracting quantitative displacement data from the system with only two frames. Optical configurations for DSPI and DS with a double aperture mask in front of the imaging lens for spatial phase shifting are proposed in this paper for the measurement of out-of-plane displacement and its first order derivative ( slope) respectively. An error compensating four-phase step algorithm is used for quantitative fringe analysis. (c) 2006 Optical Society of America.