Shape measurement by temporal phase unwrapping: comparison of unwrapping algorithms

Huntley, Jonathan M.; Saldner, Henrik O.

doi:10.1088/0957-0233/8/9/005

Cited by 121 publications

(65 citation statements)

References 7 publications

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“…This technique is presented at length by Huntley and Saldner (1997). It involves unwrapping a phase with high sensitivity by means of other phases with lower sensitivity.…”

Section: Temporal Phase Unwrappingmentioning

confidence: 99%

Tracking the free surface of time-dependent flows: image processing for the dam-break problem

Cochard

Ancey

2007

Exp Fluids

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The dam-break problem (i.e., the sudden release of a given volume of fluid down a slope) has attracted a great deal of attention from mechanicians and physicists over the past few years, with particular interest devoted to the free-surface profile and the spreading rate. Experimentally, impediments to accurate measurements of the free-surface evolution are numerous because of the significant variations in its curvature and velocity. To accurately measure the surge's free-surface variations with time, we have developed a new imaging system, consisting of a digital camera coupled with a synchronized micromirror projector. The object's surface is imaged into a camera and patterns are projected onto the surface under an angle of incidence that differs from the imaging direction. From the deformed pattern recorded by the camera, the phase can be extracted and, by using unwrapping algorithms, the height can be computed and the free surface reconstructed. We were able to measure the free surface of the flow to within 1 mm over a surface of 1.8 · 1.1 m 2 . Although the techniques used in our system are not new when taken individually, the system in its entirety is innovative and more efficient than most methods used to-date in practical applications.

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“…This technique is presented at length by Huntley and Saldner (1997). It involves unwrapping a phase with high sensitivity by means of other phases with lower sensitivity.…”

Section: Temporal Phase Unwrappingmentioning

confidence: 99%

Tracking the free surface of time-dependent flows: image processing for the dam-break problem

Cochard

Ancey

2007

Exp Fluids

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“…Especially when a multiplewavelength technique is utilized, the measurement can be performed point by point without any spatial phase unwrapping; therefore, the step-height is not a problem at all. Over the years, extensive research has been conducted on two-or multiple-wavelength phase-shifting techniques [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and temporal phase unwrapping. 15,16 All these efforts were intending to measure the step-height object or alleviate the limitations of phase unwrapping.…”

Section: Introductionmentioning

confidence: 99%

Phase unwrapping error reduction framework for a multiple-wavelength phase-shifting algorithm

Zhang

2009

Opt. Eng

108

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We address a framework to reduce the unwrapping errors of the measurement system using a digital multiplewavelength phase-shifting algorithm. In particular, the following framework is proposed: (1) smooth the raw phase by smoothing the sine and cosine images of the phase computation of the inverse tangent function; (2) locate and remove the incorrectly unwrapped points by the monotonicity condition of the phase map; (3) obtain the unwrapped phase map for the shortest wavelength without smoothing; (4) detect holes and fill them to preserve as much useful information as possible. Experiments demonstrated that the proposed framework significantly alleviated the measurement errors caused by the phase noise. KeywordsVirtual Reality Applications Center, Human Computer Interaction, structured light, phase shifting, phase unwrapping, multiple wavelength, phase error RightsCopyright 2009 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Abstract. We address a framework to reduce the unwrapping errors of the measurement system using a digital multiple-wavelength phaseshifting algorithm. In particular, the following framework is proposed: ͑1͒ smooth the raw phase by smoothing the sine and cosine images of the phase computation of the inverse tangent function; ͑2͒ locate and remove the incorrectly unwrapped points by the monotonicity condition of the phase map; ͑3͒ obtain the unwrapped phase map for the shortest wavelength without smoothing; ͑4͒ detect holes and fill them to preserve as much useful information as possible. Experiments demonstrated that the proposed framework significantly alleviated the measurement errors caused by the phase noise.

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“…15 For this system, a digital projector was used, and the phase shift as well as the wavelength can be produced precisely. However, since only the first and the last spatial frequency phase maps were used, and it was shown by Huntley and Saldner 16 that the noise plays a more significant role for this technique than the technique proposed by Zhao et al 14 Recently, Towers proposed an optimum frequency selection for the multiple wavelength methods. 17 Later they verified, by simulation, an optimum three-frequency algorithm for 3D shape measurement.…”

Section: Introductionmentioning

confidence: 99%

Digital multiple wavelength phase shifting algorithm

Zhang

2009

SPIE Proceedings

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This paper presents a digital multiple-wavelength phase-shifting technique for three-dimensional shape measurement. The projected phase-shifted fringe images have wavelengths of λ κ = W/2 κ-1 (k = 1,2,3...). The phase unwrapping is not needed for the longest wavelength because a single fringe covers the whole area. The shorter wavelength phase, φκ(x,y), is unwrapped by referring to the previously unwrapped longer wavelength phase, Φ k-1 (x,y), pixel by pixel without accessing its neighborhood pixels. Experiments demonstrate that this technique has low noise and less sensitivity to motion. It can be used to measure arbitrary step height and multiple objects simultaneously. 1, 2, 3...). The phase unwrapping is not needed for the longest wavelength because a single fringe covers the whole area. The shorter wavelength phase, φ k (x, y), is unwrapped by referring to the previously unwrapped longer wavelength phase, Φ k−1 (x, y), pixel by pixel without accessing its neighborhood pixels. Experiments demonstrate that this technique has low noise and less sensitivity to motion. It can be used to measure arbitrary step height and multiple objects simultaneously.

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Shape measurement by temporal phase unwrapping: comparison of unwrapping algorithms

Cited by 121 publications

References 7 publications

Tracking the free surface of time-dependent flows: image processing for the dam-break problem

Tracking the free surface of time-dependent flows: image processing for the dam-break problem

Phase unwrapping error reduction framework for a multiple-wavelength phase-shifting algorithm

Digital multiple wavelength phase shifting algorithm

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