Edge location to subpixel precision and analysis

Abstract

Abstract This paper proposes a new method of locating an edge in a digital image to sub‐pixel precision by using gray‐level information in the neighborhood of the edge alone. The location of the edge is determined by fitting the first derivatives of gray‐level values to a normal‐distribution curve using the least‐squares method and by regarding the location of the extreme value of the curve as the location of the edge. By comparing the proposed method with five conventional methods it is shown that the method requires the smallest amount of computation generally and minimum systematic errors in a sharp edge. The errors in an edge location measurement caused by image noises are quantized and are shown by a graph so that errors under an arbitrary condition can easily be estimated.