Bilinear interpolation centroid algorithm using for circular optical target location

摘要

In the close digital photogrammetric three-dimension coordinates measurement, the circular target is often taken as imaging feature and mounted on the measured object or the probe for 3D coordinates detection. The accuracy with which circular targets are located determines the effectiveness of measurement. Subpixel level accuracy is one of the methods that can improve the accuracy of target location. Many methods which based on subpixel edge or centroid detection have been developed and analyzed for target location, but little research focused on circular optical target location. In this research, a new algorithm named bilinear interpolation centroid algorithm was developed for circular optical target subpixel location. In this technique, the accuracy of the squared gray weighted centroid algorithm can be improved by increasing the available pixels which obtained by bilinear interpolation. The intensity profile of the imaging points and the signal to noise ratio, which affect the subpixel location accuracy, are optimized by automatic exposure control. The experiments have shown that the accuracy of this algorithm is better than the traditional centroid algorithm, and the absolute error of less than 0.01 pixels is obtained on the image of a rigid reference bar.