METHOD FOR EXTRACTING CENTER OF CIRCLE

摘要

PURPOSE:To extract a circle at a high speed and with high accuracy after elimination of the bright/dark influence by segmenting a part having a difference of density of a circle form out of a fetched original picture. CONSTITUTION:When a circle having a single size is detected out of an input picture C, a video is fetched through an industrial camera 1 for digital conversion of a bright part into a large numeric value and a dark part into a small numeric value respectively carried out by an A/D converter 2. Then 256 pieces of picture elements are written to each of 240 lines via a memory controller from the upper left part of a variable density memory 4. An area containing a density difference of the fetched picture is extracted out of an entire picture and shifted down by an amount equal to a radius with an upper position of a circle. This spot is defined as a center candidate. Then the candidate center points are successively obtained in eight directions toward the lower left part with a 45 deg. obliquely upper right position. These candidate center points are integrated and therefore the center part of a circle has many candidate points compared with other areas. Based on this fact, the variable density picture processing is carried out to extract a circle out of a picture.