New correlation coefficients designed for digital speckle correlation method (DSCM)

Digital speckle correlation method (DSCM) is based on the correlation-matching search algorithm, in which the correlation coefficient is used as a criterion for matching of two speckle patterns. The properties of the correlation coefficient affect the accuracy and the searching speed of DSCM. As many as ten different definitions of the correlation coefficient can be found in literatures but almost no comparison works are reported. In this paper, the different coefficient equations are compared and the properties of all these definitions are concluded. The comparison results may help to improve the development and application of DSCM in future. Some new correlation coefficients with better properties are then defined on the basis of the comparison.