Approaches to extending the Hough transform

The authors survey three approaches to extending the Hough transform that improve speed and reduce memory requirements. Two approaches center on the use of two-pass techniques to reduce dimensionality. One approach, specifically aimed at circle extraction, offers little more than a polar transformation. In the second approach, for ellipses, center coordinates and rotation are extracted in the first pass, and major and minor radii in the second. The final technique involves an iterative search procedure based on combining intersecting points between an approximation ellipse and its target and using a nonlinear least squares to evaluate the approximation. Each of these techniques requires less than 5% of the execution time of the equivalent Hough transform.<<ETX>>