Patent Document ID: 4618989
Application ID: 06572535
Patent Status: 1

Claim One:
1. A method of detecting an elliptical object, which comprises the following steps of: (a) transducing optical energy representative of image brightness of all locations (x, y) on an image plane including the elliptical object into electric brightness signals; (b) partially differentiating the transduced brightness signals with respect to x and y to obtain gradient signals representative of edge image brightness gradient I=(.differential.I/.differential.x, .differential.I/.differential.y); (c) generating edge vector signals representative of locations (x,y) and directions (dx,dy) of an edge vector field in perpendicular to the edge image brightness gradient I in a direction such that the bright image will always be on one side of the vector signals; (d) selecting the edge vector signals representative of all pairs of mate edge vectors having opposite directions to each other and calculating all midpoints (n.sub.1 +n.sub.2 =0) between the two selected mate edge vectors; (e) selecting a center signal having a center peak value (x.sub.o, y.sub.o) from the calculated midpoints; (f) selecting vector signals representative of the locations (x, y) and directions (dx, dy) of the edge vectors supporting the centered conics having the selected center peak value (x.sub.o, y.sub.o) from the edge vector field signals; (g) transforming the selected values (x, y, dx, dy) of the edge vector signals to a first two-dimensional (p=(YdX+XdY)/YdY, Q=XdX/YdY) space to form a first straight line and calculating all intersections of second straight lines corresponding to each transformed point on the first straight line in a second two-dimensional (H, B) space in accordance with a Hough transformation method; (h) selecting a signal having a peak value located within a specific range (H.sup.2 -B&lt;0) on the (H, B) space for detecting an ellipse; (i) calculating coefficients G=-X.sub.o -Hy.sub.o and F=-Hx.sub.o -By.sub.o of an ellipse group having the same center on the basis of the selected coefficients H, B and the selected center locations (x.sub.o, y.sub.o); (j) calculating coefficients C on the basis of the calculated coefficients H, B, G, F and the edge vector locations (x, y); and (k) selecting a peak value from the calculated coefficients C to identify a detected ellipse.