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Proceedings Paper

Accuracy of locating circular features using machine vision
Author(s): Cheryl W. Sklair; William A. Hoff; Lance B. Gatrell
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Paper Abstract

The ability to automatically locate objects using vision is a key technology for flexible, intelligent robotic operations. The vision task is facilitated by placing optical targets or markings in advance on the objects to be located. A number of researchers have advocated the use of circular target features as the features that can be most accurately located. This paper describes extensive analysis on circle centroid accuracy using both simulations and laboratory measurements. The work was part of an effort to design a video positioning sensor for NASA's Flight Telerobotic Servicer that would meet accuracy requirements. We have analyzed the main contributors to centroid error and have classified them into the following: (1) spatial quantization errors, (2) errors due to signal noise and random timing errors, (3) surface tilt errors, and (4) errors in modeling camera geometry. It is possible to compensate for the errors in (3) given an estimate of the tilt angle, and the errors from (4) by calibrating the intrinsic camera attributes. The errors in (1) and (2) cannot be compensated for, but they can be measured and their effects reduced somewhat. To characterize these error sources, we measured centroid repeatability under various conditions, including synchronization method, signal-to-noise ratio, and frequency attenuation. Although these results are specific to our video system and equipment, they provide a reference point that should be a characteristic of typical CCD cameras and digitization equipment.

Paper Details

Date Published: 1 March 1992
PDF: 13 pages
Proc. SPIE 1612, Cooperative Intelligent Robotics in Space II, (1 March 1992); doi: 10.1117/12.56760
Show Author Affiliations
Cheryl W. Sklair, Martin Marietta Astronautics Group (United States)
William A. Hoff, Martin Marietta Astronautics Group (United States)
Lance B. Gatrell, Martin Marietta Astronautics Group (United States)

Published in SPIE Proceedings Vol. 1612:
Cooperative Intelligent Robotics in Space II
William E. Stoney, Editor(s)

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