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Proceedings Paper

Three-dimensional imaging technique using optical diffraction
Author(s): Sheng Tan; Douglas P. Hart
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Paper Abstract

This paper presents a novel fast and simple technique to measure three-dimensional (3D) objects. An integrated 3D camera is built, which features a motorized off-axis rotating aperture. A regular spot pattern projection adds texture onto smooth 3D objects. When rotating, the off-axis aperture translates depth information into blurred image diameter. The displacement of each spot between two arbitrary aperture positions reveals depth. A pseudo- correlation algorithm based on optical diffraction is proposed to measure spot displacement fast and accurately. When subtracting two consecutive images of a roughly Gaussian-shaped displaced spot, the normalized subtraction intensity peak height is directly proportional to the spot displacement. The peak height to displacement calibration curve is specifically defined by optical parameters of the imaging system. Proper combination of off-axis aperture location and magnification ratio determines the size of the measurement range. Experiment observations show that the calibration curve is highly smooth and sensitive to the spot displacement at sub-pixel level. Real-time processing is possible with only order of image size arithmetic operations. The proposed technique holds potential for various industrial machine vision applications.

Paper Details

Date Published: 11 February 2002
PDF: 8 pages
Proc. SPIE 4567, Machine Vision and Three-Dimensional Imaging Systems for Inspection and Metrology II, (11 February 2002); doi: 10.1117/12.455262
Show Author Affiliations
Sheng Tan, Massachusetts Institute of Technology (United States)
Douglas P. Hart, Massachusetts Institute of Technology (United States)

Published in SPIE Proceedings Vol. 4567:
Machine Vision and Three-Dimensional Imaging Systems for Inspection and Metrology II
Kevin G. Harding; John W. V. Miller, Editor(s)

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