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Proceedings Paper

High accuracy 2D sub-pixel matching method skillfully managing error characteristics
Author(s): Hitoshi Nishiguchi; Yoshihiko Nomura; Ryota Sakamoto; Tokuhiro Sugiura
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Paper Abstract

In computer vision, many algorithms have been developed for image registration based on image pattern matching. However, there might be no universal method for all applications because of their advantages and disadvantages. Therefore, we have to select the best method suited for each task. A representative sub-pixel registration method uses one dimensional parabola fitting over the similarity measurements at three positions. The parabola fitting method could be applied to two dimensional, assuming that horizontal and vertical displacements are independent. Although this method has been widely used because of their simplicity and practical usability, large errors are involved. To avoid these errors depending on the spatial structure of image pattern, "two-dimensional simultaneous sub-pixel estimation" was proposed. However, it needs conditional branching control procedures such as scan field expansion and exception. The conditional branching control procedures make estimation instable and disturb the speed of processing. Therefore, the authors employ a paraboloid fitting: by using the least square method, a paraboloid is fitted with the image similarity values at nine points and the best matching point is obtained with sub-pixel order. It is robust against the image pattern and enables speed-up, but it still has error margin. The authors analyzed the error characteristics of the sub-pixel estimation using the paraboloid fitting. The error can be characterized by "a bias; a systematic error" and "dispersion; a random error." It was found that the magnitude of each error was different according to the sub-pixel values of the best matching positions. In this paper, based on the analysis, the authors proposed a novel accurate algorithm for 2D subpixel matching. The method does not need any iteration processes and any exception processes on runtime. Therefore, it is easy to implement the method on software and hardware. Experimental results demonstrated the advantage of the proposed algorithm.

Paper Details

Date Published: 10 September 2007
PDF: 10 pages
Proc. SPIE 6764, Intelligent Robots and Computer Vision XXV: Algorithms, Techniques, and Active Vision, 67640K (10 September 2007); doi: 10.1117/12.730602
Show Author Affiliations
Hitoshi Nishiguchi, Mie Univ. (Japan)
Yoshihiko Nomura, Mie Univ. (Japan)
Ryota Sakamoto, Mie Univ. (Japan)
Tokuhiro Sugiura, Mie Univ. (Japan)

Published in SPIE Proceedings Vol. 6764:
Intelligent Robots and Computer Vision XXV: Algorithms, Techniques, and Active Vision
David P. Casasent; Ernest L. Hall; Juha Röning, Editor(s)

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