Surface Deformation Measurement Based On Digital Speckle Pattern Interferometry

Digital speckle pattern interferometry (DSPI) for surface deformation measurement is studied in this paper. Digital speckle pattern interferometry is combined with speckle interference technology, precision testing technology and computer image processing technology. It has smaller error and higher accuracy, so it can be used in measuring micron dimension deformation. we design three kinds of optical devices based on principle of DSPI, they are composed of Twyman-Green,Mach-Zehnder and a computer-controlled real-time speckle interference system and used in rough surface deformation measurement. In order to achieve the digital speckle pattern interferometry, the device receives the interference fringes by CCD and input the fringes to the computer in order to carry on digital image processing. According to the characteristic of the speckle pattern and it is high noise, we present subtraction method to process image, and the correlative fringe pattern include object's deformation information is obtained. Then, we can count the deformation by the correlative fringe. At last, this paper applies filter program wrote by Matlab, eliminates the effects of digital speckle interference correlative fringe pattern effectively which caused by pellet noise, improves the contrast of fringe and increases the definition of image, based on the study of the de-noising ability of all kinds de-noising algorithm in spatial domain and frequency-domain.