METHOD FOR CHARACTERIZING MATERIAL BY ANALYSIS OF SPECKLES

摘要

The invention proposes a method for characterizing material in which a surface is formed, comprising the steps of:
projecting a coherent light beam onto the surface to generate on said surface speckles resulting from interferences of the light beams diffused by said surface,acquiring an image of said surface on which the speckles appear,processing said image to compute at least one characterization criterion of the material, andfrom criteria, determining the material constituting the surface,

in which the processing step of the image comprises:
computation of an autocorrelation function of the light intensity on the image and computation of the value of at least one criterion set up from said function, andcomputation of the value of at least one criterion representative of a phase shift distribution of the light beams diffused by the surface.

主权项

1. A method for characterizing material in which a surface is formed, comprising the steps of:
projecting a coherent light beam onto the surface to generate on said surface speckles resulting from interferences of the light beams diffused by said surface, acquiring an image of said surface on which the speckles appear, processing said image to compute at least one characterization criterion of the material, and from criteria, determining the material constituting the surface, in which the processing step of the image comprises: computation of an autocorrelation function of the light intensity on the image and computation of the value of at least one criterion set up from said function, said computation comprising:
setting up an autocorrelation matrix of the light intensity of the image,computation of the discrete cosine transform of said matrix, andcomputation of the value of a characterization criterion such as the average on the image of the matrix trace obtained by the discrete cosine transform of the autocorrelation matrix, and computation of the value of at least one representative criterion of a phase shift distribution of the light beams diffused by the surface, said computation comprising computation of a wavelet transform of the image, and computation of the value of at least one criterion from the following group:
average of the phases of the wavelet coefficients on the image, orstandard deviation of the phases of the wavelet coefficients on the image.