Method and apparatus for reconstruction of three-dimensional surfaces from interference fringes
First Claim
1. The fully automatic method of processing a pair of optically generated two-dimensional continuous, branched fringe patterns representative of a three-dimensional surface comprising the steps of:
- A. transforming a pair of optically generated two-dimensional fringe patterns into first and second electronic images, said pair of fringe patterns representing the same three-dimensional surface, but containing sufficient information to permit the topography of said three-dimensional surface to be determined therefrom;
B. digitizing the first and second electronic images to form first and second arrays of integers;
C. thresholding the digitized images to transform the integers of the first and second arrays to either the digit one or the digit zero;
D. segmenting electronically the thresholded images to define first and second sets of fringes;
E. detecting electronically the edges of the fringes of the first and second sets of fringes to define first and second sets of contours; and
F. sequencing electronically the first set of contours by comparing the second set of contours to the first set of fringes to determine the spatial coordinates of the three-dimensional surface.
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Abstract
A fully automatic method for rapidly and unambiguously interpreting fringe patterns, including those having branched fringes, is provided. The information from the fringe patterns processed by the method of the invention can be used in testing, surface characterization and inspection applications. Further processing of the information from the two-dimensional fringe patterns yields information from which the three-dimensional surface can be quantitatively reconstructed for further use such as for display, as in microscopy, or as input for computer-aided design and computer-aided manufacture. Apparatus for conducting the method of the invention is also provided.
85 Citations
23 Claims
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1. The fully automatic method of processing a pair of optically generated two-dimensional continuous, branched fringe patterns representative of a three-dimensional surface comprising the steps of:
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A. transforming a pair of optically generated two-dimensional fringe patterns into first and second electronic images, said pair of fringe patterns representing the same three-dimensional surface, but containing sufficient information to permit the topography of said three-dimensional surface to be determined therefrom; B. digitizing the first and second electronic images to form first and second arrays of integers; C. thresholding the digitized images to transform the integers of the first and second arrays to either the digit one or the digit zero; D. segmenting electronically the thresholded images to define first and second sets of fringes; E. detecting electronically the edges of the fringes of the first and second sets of fringes to define first and second sets of contours; and F. sequencing electronically the first set of contours by comparing the second set of contours to the first set of fringes to determine the spatial coordinates of the three-dimensional surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for fully automatically processing a pair of optically generated two-dimensional continuous, branched fringe patterns representative of a three-dimensional surface comprising:
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A. means for transforming a pair of optically generated two-dimensional fringe patterns into first and second electronic images, said pair of fringe patterns representing the same three-dimensional surface, but containing sufficient information to permit the topography of said three-dimensional surface to be determined therefrom; B. means for digitizing the first and second electronic images to form first and second arrays of integers; C. means for thresholding the digitized images to transform the integers of the first and second arrays to either the digit one or the digit zero; D. means for segmenting electronically the thresholded images to define first and second sets of fringes; E. means for detecting electronically the edges of the fringes of the first and second sets of fringes to define first and second sets of contours; F. means for sequencing electronically the first set of contours by comparing the second set of contours to the first set of fringes to determine the spatial coordinates of the three-dimensional surface; and G. bus means for interconnecting said means for transforming, digitizing, thresholding, segmenting, detecting and sequencing. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A computer-aided interference device for fully automatically producing a displayed, shaded, smoothed and manipulatable quantitative representation of a three-dimensional surface from a pair of optically generated two-dimensional fringe patterns comprising:
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(A) means for transforming a pair of optically generated two-dimensional fringe patterns into first and second electronic images, said pair of fringe patterns representing the same three-dimensional surface, but containing sufficient information to permit the topography of said three-dimensional surface to be determined therefrom; (B) means for digitizing the first and second electronic images to form first and second arrays of integers; (C) means for thresholding the digitized images to transform the integers of the first and second arrays to either the digit one or the digit zero; (D) means for segmenting electronically the thresholded images to define first and second sets of fringes; (E) means for detecting electronically the edges of the fringes of the first and second sets of fringes to define first and second sets of contours; (F) means for sequencing electronically the first set of contours by comparing the second set of contours to the first set of fringes to determine the spatial coordinates of the three-dimensional surface; (G) triangulating means including; (a) means for obtaining from the sequencing means the contours defining a fringe, each contour being defined by a set of nodes; (b) means for calculating the distances between unconnected node pairs and listing in order of increasing distance; and (c) means for connecting said node pairs beginning with the node pair having the shortest distance and progressing through said list connecting node pairs of increasing length excluding those node pairs that would intersect previously connected node pairs or contours until all possible eligible unconnected node pairs are connected to form a triangulated polygonal representation of the three-dimensional surface; (H) visualizing means including means for displaying, smoothing, shading, and manipulating the triangulated polygonal representation of the three-dimensional surface; and (I) bus means for interconnecting said means for transforming, digitizing, thresholding, segmenting, detecting, sequencing, triangulating, and visualizing. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification