The Study Of Laser Speckle Characteristics And The Filtering Of Interference Fringes

Nondestructive examination (NDE) has become an important method for industrial manufacture. In many situations, as the contact examination lacks maneuverability and practicability, NDE is an absolutely necessary method. Electronic speckle pattern interferometry (ESPI) is a new technology consisting of computer image processing, laser technology and. ESPI has become the most important technology in holographical speckle metrology because of its merit of simple operation, high automation and real time, and can be used in static and dynamic test.In this paper, detailed study has been performed for the theory of ESPI, and the relationship between the ESPI and the holographical interferometry, the ESPI and the speckle photography. The laser speckle characteristics have been studied based on speckle theory, and the law of speckle has been found. As the contrast and visibility of speckle interference figure are directly influenced by speckle characteristics, a conclusion has been accepted by studying the relationship between speckle pattern and speckle interference figure, and then an effective filter has been proposed by processing interference pattern with different filter. The conclusion can be used in digital speckle interferometrical testing.