ELLIPSE-LIKE CURVE RECOGNITION BY CALCULATION OF DISTANCES OF POINTS ON THE CURVE FROM FOCI

After calculation of coordinates of points on a plane curve, a pattern recognition device calculates (S3) coordinates of foci and a major axis of a candidate ellipse and, (S4) until all points are used, (S5) a sum of distances between said point and the foci. After calculation of (S6) of the sum to the major axis, (S7) a variance of such ratios is calculated to judge (S8) whether or not the plane curve is a geometric ellipse. A mean value may be substituted for the variance. The variance may be calculated as regards sums calculated for all points. Preferably, the foci and the major axis are calculated by calculating (S1) an inscribed and subsequently (S2) a circumscribed rectangle. In this event, the candidate ellipse is inscribed in the circumscribed rectangle.