Epipolar reconstruction of 3D structures

• US 5,559,334 A
• Filed: 05/22/1995
• Issued: 09/24/1996
• Est. Priority Date: 05/22/1995
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gupta, Rajiv, Hartley, Richard I.
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Bruce, David Vernon
• Application Number:
  US08/447,021
• Time in Patent Office: 491 Days
• Field of Search: 250/358.1, 250/359.1, 250/360.1, 378/62, 378/901
• US Class Current: 250/360.1
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]

Abstract

A method of reconstructing selected features of a part manufactured according to a CAD model involves acquiring a set of linear push broom (LPB) projection images of the part acquired at different angles about an axis of rotation passing through the part. Acquiring a set of matrices M_j j=1 . . . N, each of which maps 3D coordinates of the part to screen coordinates of one of the projection images. Reconstruction of 3D structures from the projection images requires identification of screen coordinates of each image which correspond to a point of the structure of the part to be reconstructed. Back projecting these screen coordinates modified by the distortion inherent in the LPB imaging device. This is accomplished by selecting a screen coordinate on a feature desired to be reconstructed. Computing a ray passing through the selected screen coordinate through an imaging center. Using each M matrix to map this ray to a hyperbola on the other images. The hyperbola is then scanned until the desired feature is encountered. This second screen location of this projection image corresponds to the first selected screen location. A second ray through the second screen coordinate is constructed. Where it intersects the first ray identifies the 3D reconstruction point. This is repeated for a number of points to create a reconstruction of the selected feature.

Claims

1. A method of reconstructing structures of a part from N linear pushbroom (LPB) projection images, where N is greater than 1, given the mapping matrices M_j for each of the projection images j=1 . . . N comprising the steps of:

a) acquiring a plurality of linear pushbroom images at different angles about an axis of rotation passing through the part;

b) selecting a first set of screen coordinates (u₁,v₁) having an intensity I of a first projection image being part of a feature desired to be reconstructed;

c) creating a first ray passing through the selected screen coordinate and through a center of projection;

d) multiplying a plurality of points along the ray by the matrix M_j to result in substantially a hyperbola on a second projection image;

e) correlating intensities along the hyperbola to intensity I to determine a second set of screen coordinates (u₂,v₂) on the second projection image where the hyperbola intersects the selected structure, the second set of screen coordinates (u₂,v₂) corresponding to the same point on said part as the first set of screen coordinates (u₁,v₁)

f) creating a second ray passing through the second set of screen coordinates (u₂,v₂) and through a center of projection;

g) identifying a 3D location where the rays intersect as the reconstructed point; and

h) repeating steps "b"-"g" for a plurality of points on the desired feature; and

i) displaying the 3D reconstructed point to result in a reconstructed 3D structure.

2. A method of reconstructing structures of a part from N linear pushbroom (LPB) projection images, where N is greater than 1, given the mapping matrices M_j for each of the projection images j=1 . . . N comprising the steps of:

a) acquiring a plurality of linear pushbroom images at different angles about an axis of rotation passing through the part;

b) selecting a first set of screen coordinates (u₁,v₁) having an intensity I on an initial projection image, the first set of coordinates being part of a feature desired to be reconstructed;

c) creating a first ray passing through the selected screen coordinate and through a center of projection;

d) multiplying a plurality of points along the ray by the matrix M_j to result in a hyperbola on another projection image j;

e) correlating intensities along the hyperbola to intensity I to determine a jth set of screen coordinates (u_j,v_j) on projection image j where the hyperbola intersects the selected structure, the jth set of screen coordinates (u_j,v_j) corresponding to the same point on said part as the first set of screen coordinates (u₁,v₁);

f) creating a jth ray passing through the jth set of screen coordinates (u_j,v_j) and through a center of projection;

g) repeating steps "d"-"f" for a plurality of projection images;

h) identifying a 3D location where the rays intersect as the reconstructed point; and

i) repeating steps "b"-"h" for a plurality of points on the desired feature; and

j) displaying the 3D reconstructed point to result in a reconstructed 3D structure.