Optical three-dimensional profilometry method based on processing speckle images in partially coherent light, and interferometer implementing such a method

摘要

An optical three-dimensional profilometry method in which are recorded SPECKLE images formed by the interference, due to different optical paths, of the rays reflected/diffused by a rough object and the rays generated by a beam source. The method presents a number of processing steps including the steps of digitizing (120) a first SPECKLE image, modifying (130) the optical path difference, and digitizing (140) a second SPECKLE image recorded after modifying (130) the optical path difference. The difference in the modulus of the corresponding pixels (Ix(i,j) and Ix+1(i,j)) of the first and second digitized images is determined to generate a difference image which is subsequently analyzed (160), a first arbitrary value (A) is assigned to all the difference image pixels (Id(i,j)) exceeding a given threshold value (Is), and a second arbitrary value (B) is assigned to all the difference image pixels (Id(i,j)) of a value below the threshold (Is). The binary image so generated is processed to generate (170) an artificial image (Ma) in which all the binary image pixels (Ib(i,j)) equal to the second arbitrary value (B) are assigned a zero value, and all the binary image pixels (Ib(i,j)) equal to the first arbitrary value (A) are assigned a current processing step value (STEP). The processing steps are repeated cyclically for a predetermined number (STEP-MAX) of steps to generate a depth map (Ma) presenting a number of pixels, each presenting a grey level (Ia(i,j)) corresponding to the last processing step in which the threshold was exceeded, and the depth map contains three-dimensional information relative to the profile of the rough object (20) under examination.