Speckle metrology.

When a laser beam is encountered by a diffusing object, a granular pattern is formed which is a major source of noise. This noisy granular pattern is known as laser speckles. This is suitably applied in metrology. Since laser light is highly coherent, the light reaching at any point from the entire surface interferes forming an intensity variation. This variation when combined with the resolution of the camera, gives the random granular structure. As a result of this effect, even an uniformly illuminated surface appears with a noisy background. Electronic speckle pattern interferometry is a novel method where image is processed electronically using a television vidicona. In the latest development, speckles are magnified using lenses and a high resolution TV camera-monitor system is used to observe speckles directly.