A Sub-Pixel Extraction Method for the Center of the Circular Structure from Spot Array Calibration Target
Yang Chuan Liu, Xin Qiang Gao, Chuan Xu, Wei Fu, Yun Tian Teng, Hong Yang, Tao Zhang · Applied Mechanics and Materials · 2012
The imaging measurement system must be calibrated before application. In calibration procedure, sub-pixel center extraction is the crucial step for the final accuracy. In this paper, a new sub-pixel extraction method is proposed. Edge detection at pixel level is obtained using LOG operator, then sub-pixel edge detection is realized using the Facet model. Finally, the least squares ellipse fitting is operated on the sub-pixel edge to determine the sub-pixel center. Experiment on a series of simulated images indicates that this algorithm is able to realize the center location accuracy of 0.01-0.02 pixel, and meets the requirement of sub-pixel level.