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Proceedings Paper

A new three-dimensional shape measurement method based on double-frequency fringes
Author(s): Biao Li; Jie Yang; Haitao Wu; Yanjun Fu
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Paper Abstract

Fringe projection profilometry (FPP) is a rapidly developing technique which is widely used for industrial manufacture, heritage conservation, and medicine etc. because of its high speed, high precision, non-contact operation, full-field acquisition, and easy information processing. Among the various FFP methods, the squared binary defocused projection method (SBM) has been promptly expanding with several advantages: (1) high projection speed because of 1-bit grayscale fringe; (2) eliminating nonlinear gamma of the projector for the defocusing effect. Nevertheless, the method is not trouble-free. When the fringe stripe is wide, it brings down the fringe contrast and is difficult to control the defocused degree, resulting in a low measurement accuracy. In order to further improve high-speed and high-precision three-dimensional shape measurement, this paper presents a new three-dimensional shape measurement method based on double-frequency fringes projection. This new method needs to project two sets of 1-bit grayscale fringe patterns (low-frequency fringe and high-frequency fringe) onto the object surface under slightly defocused projection mode. The method has the following advantages: (1) high projection speed because of 1-bit grayscale fringe; (2) high measurement precision for selectively removing undesired harmonics. Low-frequency fringe is produced by error-diffusion dithering (Dithering) technique and high-frequency fringe is generated by optimal pulse-width modulation (OPWM) technique. The two kinds of fringe patterns have each superiorities and flaws. The low-frequency fringe has a low measurement accuracy, but the continue phase can be easily retrieved. However, the property of high-frequency fringe and low-frequency fringe is the opposite. The general idea of this method proposed is as follows: Because the both fringes test the same object, the height is the same. The low-frequency fringe can be used to assist the high frequency fringe to retrieve continue phase map, then the three-dimensional shape information of the object can be obtained. Theory analyzes the mathematical principle of error-diffusion dithering technique, optimal pulse-width modulation technique and three-dimensional reconstructed algorithm based on double-frequency fringes projection. A second-hand mouse was used to test the proposed method. The experiment results show that the three-dimensional shape measurement method combining OPWM technique and Dithering technique can achieve fast-speed and high-precision three-dimensional shape measurement.

Paper Details

Date Published: 8 October 2015
PDF: 8 pages
Proc. SPIE 9677, AOPC 2015: Optical Test, Measurement, and Equipment, 96770H (8 October 2015); doi: 10.1117/12.2197718
Show Author Affiliations
Biao Li, Nanchang Hangkong Univ. (China)
Jie Yang, Nanchang Hangkong Univ. (China)
Haitao Wu, Nanchang Hangkong Univ. (China)
Yanjun Fu, Nanchang Hangkong Univ. (China)

Published in SPIE Proceedings Vol. 9677:
AOPC 2015: Optical Test, Measurement, and Equipment
Sen Han; Jonathan D. Ellis; Junpeng Guo; Yongcai Guo, Editor(s)

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