METHOD AND APPARATUS OF DETERMINING THE TRUE EDGE LENGTH OF A BODY

A method and apparatus for determining the true edge length of a body subtended by two other body edges comprises exposing the body to a beam of light such that the edge is imaged by an optical system for projecting a linear section across the body as a silhouette-like image onto a linear array of photosensitive detectors. The image is usually blurred due to diffraction effects. The body is initially positioned in focus and then scanned moving the array provide an image of at least a portion of the desired edge to define a reference line representing the location of the edge. The array is then moved in scanned sequence from that reference line to provide fifty percent (50%) intensity level data points to define the other body edges. Lines are fitted through such data points and extended to intersect the reference line to determine the true length of the edge even with a blurred image of portions of that edge.