Detecting Methods for Elliptical Patterns Using Feature of Conjugate Diameter

Abstract

Efficient methods are proposed for elliptical patterns using the properties of conjugate diameters. They are the center detecting algorithm (CDA) and the form detecting argorithm (FDA). The (CAD) uses the property of an ellipse that two edge elements at the central symmetric have tangential lines in opposite directions. The (FDA) uses a property of conjugate diameters. The slope angle (θ) of the elliptical axis is computed using two pairs of conjugate diameter slopes. The semi-major diameter and semi-minor diameter can be computed using the coordinates of the ellipse line elements. These algorithms are used on to some sample images, and the performances of the two methods are compared. Elliptical patterns can be stably detected from complex line drawings, and can also be detected accurately from chipped patterns.