Simplified Carre's method for phase extraction

A phase-shifting algorithm for speckle patterns with a constant but unknown phase shift is proposed. The algorithm is based on the well known Carre's method. Prior to applying the phase-shifting algorithm a speckle pattern background is removed. In this process, manual intervention is minimal and high computational speed is achieved. In addition, high-frequency phase signal would not be filtered out in the noise reduction process as is the case in bandpass filtering technique. Its validity is tested on the deformation measurement using digital speckle shearing interferometry (DSSI).