Contour radiography: a system for determining 3-dimensional contours of an object from its 2-dimensional images

Apparatus for reconstruction of three-dimensional coordinates of an object, which object has a radiographically identifiable contour, the apparatus comprising:

• an X-ray source for emitting X-rays, said source being movable between a first and a second position;
• X-ray film for exposure to said X-rays;
• the object being located between the X-ray source and the X-ray film;
• calibration means located between the X-ray source and the X-ray film for calibrating the spatial location of the X-ray source;
• whereby the X-ray film is exposed in said first and second positions so as to obtain respective first and second two-dimensional contour images of the radiographically identifiable contour on said X-ray film at spaced locations, and whereby calibrations images of the X-ray source are obtained on said X-ray film;
• means for providing two-dimensional coordinates of said first and second contour images and of said images of said calibration means;
• processing means for processing the two-dimensional coordinates of said first and second images in which a two-dimensional coordinate selected on one of said first and second images is correlated with a two-dimensional coordinate on the other of said first and second images;
• correspondence means for performing said correlation in which an algorithm is used to determine a minimum value for the length of the normal transversal drawn between skew rays which connect the X-ray source in said first and second positions to respective points on the first and second contour images, said minimum value thereby defining a corresponding pair of two-dimensional coordinates for each three-dimensional coordinate, which three-dimensional coordinate represents a point on the identifiable contour of the object, whereby corresponding coordinates on said first and second images are identified and processed in pairs, each processed coordinate pair and the spatial coordinates of the X-ray source providing the three-dimensional coordinate of a point on the identifiable contour.

Apparatus for reconstruction of three-dimensional coordinates of an object which has a radiographically identifiable contour, the apparatus comprising:

• a first and a second X-ray source for emitting X-rays;
• an X-ray film for exposure to said X-rays, the object with the radiographically identifiable contour being located between the X-ray source and the X-ray film;
• calibration means located between the X-ray source and the X-ray film to determine the locations of the first and second X-ray sources;
• said X-ray film being exposed to the first and second X-ray sources whereby respective first and second two-dimensional contour images of said radiographically identifiable contour are obtained on said X-ray film at spaced locations, and whereby calibration images of said calibration means are obtained on said X-ray film;
• means for providing two-dimensional coordinates of said first and second contour images and of said calibration images;
• processing means for processing the two-dimensional coordinates of said first and second images in which a two-dimensional coordinate selected on one of said first and second images is correlated with a two-dimensional coordinate on the other of said first and second images;
• correspondence means for performing said correlation in which an algorithm is used to determine a minimum value for the length of the normal transversal drawn between skew rays which connect the first and the second X-ray sources to respective points on said first and second contour images, said minimum value thereby defining a corresponding pair of two-dimensional coordinates for each three-dimensional coordinates of a point on the identifiable contour of the object, whereby corresponding coordinates on said first and second images are identified and processed in pairs, each process coordinate pair and the spatial coordinates of the first and second X-ray sources providing the three-dimensional coordinate of a point on said identifiable contour.

A method of reconstructing the three-dimensional coordinates of a point on an identifiable contour of an object, the method comprising the steps of:

• irradiating the contour from at least two spaced locations;
• determining the spatial coordinates of the respective spaced locations;
• forming a two-dimensional image of the contour for each spaced location;
• digitizing the coordinates of the two-dimensional images;
• selecting a first point on one of said contour images;
• searching on the other of said contour images for a point such that an algorithm provides a minimum value whereat the length of a normal transversal drawn between skew rays which connect the two spaced locations to said point is at a minimum, said minimum value defining a corresponding pair of points for a particular point on the contour;
• processing said corresponding pair with said spatial coordinates of the radiation means to provide said three-dimensional coordinates of said point on the contour.