Study On The Spatial Moment-Based Operator For Image Measurement

Image measurement is a new measuring technology. It based on the optics, and syncretized electronics, computer science, laser science, and image processing technology, then, the image measuring system is formed. Edge location is a key skill in the image measurement, and locating edge in pixel is satisfactory in common usage. But with the development of the minute machining technology, the measuring precision is highly strengthened, and the sub-pixel technology is introduced in image measuring system, which can locate edge in sub-pixel. Especially, spatial moment-based edge operator is widely used because of the advantage in the higher measuring precision and the measuring data being not influenced by noises.In this paper, based on the principle of the spatial moment-based edge operator, the improvement has been made in two faces. Firstly, the causes of principle error about the spatial moment-based edge operator are explored and the principle error function on random angle of edge is proposed, some important properties about the error function are also discussed. Using the improved algorithm in edge location, the computing complexity is reduced by avoiding search efforts when using two dimensions error table, and the measuring accuracy is increased. Secondly, by the analysis of the effect on the spatial moment-based edge operator in sampling and quantifying, some important conclusion is also made, which can give inspiration on the choice of the edge points before calculating the parameters. By the experimental study about the validity and accuracy of the improving operator proposed by authors, the increasing of measuring accuracy is remarkable.