A digital speckle shearing interferometer is developed using a dynamic binary phase grating realized by an electrically addressed, twisted nematic liquid-crystal spatial light modulator as the shearing element. The standard phase-shifting algorithm can be easily achieved by changing the grating pattern displayed on the spatial light modulator. The method has a number of advantages including variable sensitivity, no moving part, and no requirement for calibration of the value of the phase shift. The error due to the unexpected diffraction order is also discussed.
S. A. Zhao,
Po Sheun Chung,
"Digital speckle shearing interferometer using a liquid-crystal spatial light modulator," Optical Engineering 45(10), 105606 (1 October 2006). https://doi.org/10.1117/1.2360940