Recent Results in Precision Measurements of Edges, Angles, Areas and Perimeters

Abstract

This paper presents recent results in precision measurements using computer vision. An edge operator based on two-dimensional spatial moments is used. This operator can locate correctly modeled edges to hundredths of a pixel. This accuracy is unaffected by additive or multiplicative changes to the data values. The precision is achieved by correcting for many of the deterministic errors caused by non-ideal edge profiles using a look-up table to correct the original estimates of edge orientation and location. This table is generated using a synthesized edge which is located at various subpixel locations and various orientations. The edge locator is then used to estimate area and perimeter of imaged objects. Area and perimeter are also measured using averages of estimates from binary images generated by thresholding at many gray values. This method of threshold decomposition is compared to the edge detection methods. The application of these techniques to measurement of imaged machined metal parts is also presented.