Filtering Methods of the Digital Speckle fringe Pattern

In modern digital speckle measurement method, we usually adopt subtraction to derive a digital speckle fringe pattern, which is information carrier for postprocessing and inherently full of multiplicative noise. Noise reduction is needed before next processing step in order to guarantee the measurement precision. Which filtering methods should be adopted is much important. The authors expatiate some often used filtering methods in the digital speckle fringe pattern after reading a lot of concerned papers. Some representative filtering methods are selected for the purpose and the results are analyzed. At the end of the paper, the development direction of the filtering methods of digital speckle fringe pattern is presented.