Averaging double-exposure speckle interferograms.
Speckle-fringe quality can be improved by averaging many statistically independent interferograms together, which are generated by shifting the object's illumination angle. A technique applicable to double-exposure speckle interferograms obtained from processing two speckle patterns is described. It utilizes a computer-controlled stepping motor to tilt the object illumination, which is repeatable to lambda/100. Results are shown for double-exposure interferograms corresponding to mechanical deformations and vibrations. A significant increase in the fringe visibility is gained.
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