Optical methods in experimental mechanics Part 24: Demonstrations of laser speckle phenomena

Laser speckle is a salt-pepper pattern that contaminates images made with laser illumination. In this paper, simple experiments that demonstrate basic laser speckle phenomena are described. The demonstration experiments require only a minimal laser, a beam-expanding lens such as a microscope objective, a screen for viewing the expanded laser beam and stability of the system. It is also emphasized that speckle brightness changes with longitudinal motion of an object forms the basis of several measurement techniques including electronic speckle pattern interferometry (ESPI), digital speckle pattern interferometry (DSPI), electronic and digital speckle shearography (DSS) and phase shifting methods that enhance these techniques.