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

Peirong Jia; Jonathan Kofman; Chad English; Adam Deslauriers

doi:10.1117/12.649009

6 December 2005 Two-step triangular phase-shifting method for 3-D object-shape measurement

Peirong Jia, Jonathan Kofman, Chad English, Adam Deslauriers

Proceedings Volume 6049, Optomechatronic Sensors and Instrumentation; 60490G (2005) https://doi.org/10.1117/12.649009
Event: Optomechatronic Technologies 2005, 2005, Sapporo, Japan

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.

Citation Download Citation

Peirong Jia, Jonathan Kofman, Chad English, and Adam Deslauriers "Two-step triangular phase-shifting method for 3-D object-shape measurement", Proc. SPIE 6049, Optomechatronic Sensors and Instrumentation, 60490G (6 December 2005); https://doi.org/10.1117/12.649009

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