1. A method for detecting the position and orientation of a geometric figure, comprising: sequentially producing pixel coordinates with respect to an orthogonal coordinate system of pixels which make up an image of said geometric figure; identifying special coordinates of said pixel coordinates; and comparing said coordinates of said certain characteristic pixels with stored information to detect the position and the orientation of said geometric figure, wherein said certain characteristic pixels are: that pixel, of those which have the least value of one coordinate, which has the least value of the other coordinate; that pixel, of those which have the greatest value of said one coordinate, which has the least value of said other coordinate; that pixel, of those which have the least value of said other coordinate, which has the least value of said one coordinate; and that pixel, of those which have the greatest value of said other coordinate, which has the least value of said one coordinate.