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Proceedings Paper

Two-step triangular phase-shifting method for 3-D object-shape measurement
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Paper Abstract

Traditional sinusoidal phase-shifting algorithms involve the calculation of an arctangent function to obtain the phase, which results in slow measurement speed. This paper presents a novel high-speed two-step triangular phase-shifting approach for 3-D object measurement. In the proposed method, a triangular gray-level-coded pattern is used for the projection. Only two triangular patterns, which are phase-shifted by 180 degrees or half of the pitch, are needed to reconstruct the 3-D object. A triangular-shape intensity-ratio distribution is obtained by calculation of the two captured triangular patterns. Removing the triangular shape of the intensity ratio over each pattern pitch generates a wrapped intensity-ratio distribution. The unwrapped intensity-ratio distribution is obtained by removing the discontinuity of the wrapped image with a modified unwrapping method commonly used in the sinusoidal phase-shifting method. An intensity ratio-to-height conversion algorithm, which is based on the traditional phase-to-height conversion algorithm in the sinusoidal phase-shifting method, is used to reconstruct the 3-D surface coordinates of the object. Compared with the sinusoidal and trapezoidal phase shifting methods, the processing speed is faster with similar resolution. This method therefore has the potential for real-time 3-D object measurement. This has applications in inspection tasks, mobile-robot navigation and 3-D surface modeling.

Paper Details

Date Published: 6 December 2005
PDF: 10 pages
Proc. SPIE 6049, Optomechatronic Sensors and Instrumentation, 60490G (6 December 2005); doi: 10.1117/12.649009
Show Author Affiliations
Peirong Jia, Univ. of Ottawa (Canada)
Jonathan Kofman, Univ. of Ottawa (Canada)
Univ. of Waterloo (Canada)
Chad English, Neptec Design Group Ltd. (Canada)
Adam Deslauriers, Neptec Design Group Ltd. (Canada)

Published in SPIE Proceedings Vol. 6049:
Optomechatronic Sensors and Instrumentation
Yasuhiro Takaya, Editor(s)

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