SUBPIXEL PRECISION OF STRAIGHT-EDGED SHAPES FOR REGISTRATION AND MEASUREMENT

The precision by which a region is located or measured on the image pl ane is limited by the sampling density. In this paper, the worst-case precision errors are determined for calculating the average image loca tion of an edge, line, and straight-edged region. For each case, it is shown how the worst-case error can be minimized as a function of the geometric parameters. These results can be used to determine the worst case error by which the location of a known shape is measured. Anothe r application is to design shapes for use in registration, such as fid ucial marks used in electronic assembly. The main conclusion of this p aper is that, to achieve better precision, measurement of a straight-e dged region should be made at an angle askew to the sampling axis (not 0, 45, or 90 degrees) and this should be at a certain length that is a function of this skew angle.