Three-map absolute moiré contouring

Xie, Xinjun; Atkinson, John; Lalor, Michael J.; Burton, David R.

doi:10.1364/ao.35.006990

Cited by 20 publications

(10 citation statements)

References 18 publications

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“…Several authors proposed solutions for this problem by combining two or more recordings with different pitch into new advanced unwrapping algorithms [6,20], making it possible to unambiguously unwrap the height maps by comparison and manipulation of the recordings with different height resolution and inter fringe plane distance. Moiré recordings with different grating pitch were previously achieved by physically interchanging the grids, or by ingenious methods like rotating the grid [29], projecting a superposition of several grids in different colors [30], or by encoding the projected grid with two frequencies [6]. With our computerized liquid crystal grids, the implementation of these advanced phase unwrapping algorithms becomes easy and fast, and needs no physical interaction anymore with the optical setup: One simply needs to change the virtual grid in the computer and the LCG's have another pitch with corresponding sensitivity.…”

Section: Discussionmentioning

confidence: 99%

Moiré profilometry using liquid crystals for projection and demodulation

Buytaert¹,

Dirckx²

2008

Opt. Express

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A projection moiré profilometer is presented in which both projection and optical demodulation are realized with liquid crystal light modulators. The computer generated grids, realized on thin film transistor matrices, allow phase-stepping and discrete grid averaging without the need for any mechanically moving component. Spatial line pitch and phase steps can thus be readily adjusted to suit the measurement precision and object geometry. The device is able to perform topographic measurements with a height resolution of 15 microm on every pixel of the recording device.

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Section: Discussionmentioning

confidence: 99%

Moiré profilometry using liquid crystals for projection and demodulation

Buytaert¹,

Dirckx²

2008

Opt. Express

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“…Finally, the errors and limitations of this method are yet to be studied in further detail. 8. ACKNOWLEDGEMENT…”

Section: Discussionmentioning

confidence: 99%

<title>Digital filters for surface shape recovery from phase-modulated structured light</title>

1997

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A rarely used fringe demodulation method which uses similar technique to phase demodulation in satellite communications is demonstrated in this paper. The processing is done in the space domain utilising zero phase digital filters. In this paper, a recursive pole-zero placement digital filter design method has been employed, and the filters have been applied to both 1-D simulated signals and real 2-D images. The results are explained and suggestions to further improve either the quality or speed of the method are also presented. Two methods of producing zero-phase digital filters are explained which is important in preserving the integrity of an image. Theoretical derivation and detailed analysis of the demodulation method and filter design are presented. Images are included as to give a better understanding of the approach. Finally, comments, improvements and comparisons of the method are included.

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“…An excellent general overview of the technique can be found in [5]. Substantial studies [5][6][7][8] have been done to overcome the difficulty as detailed above. But the cost of the solution is the limited measurable depth range or a complicated setup.…”

Section: Introductionmentioning

confidence: 99%

Shadow moiré technology based fast method for the measurement of surface topography

Zhao

et al. 2013

Appl. Opt.

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We present a fast phase-shifting shadow moiré device for surface topography measurement. In our setup, multiple light sources located at different positions are controlled to illuminate the grating sequentially. Therefore, the phase shift across the field of view shadow moiré is introduced by changing the distance between the light source and the camera. Thanks to the necessity for mechanical movement being omitted here, the proposed setup can capture the phase-shifting fringe patterns at a high speed. However, affected by the bias modulation and amplitude modulation of the captured fringe patterns, the phase of interest cannot be demodulated by the standard phase-shifting algorithm directly. Thus the principal component analysis (PCA) demodulation approach is used to extract the wrapped phase map. In addition, we develop an iterative procedure to reduce the detuning error introduced by the PCA algorithm. The proposed method implements a fast way to determine the topography of a surface through a simple experimental setup. It is applied to obtain an external surface of a specimen. Both the simulation results and the experimental results show the validity of the proposed technique.

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Three-map absolute moiré contouring

Cited by 20 publications

References 18 publications

Moiré profilometry using liquid crystals for projection and demodulation

Moiré profilometry using liquid crystals for projection and demodulation

<title>Digital filters for surface shape recovery from phase-modulated structured light</title>

Shadow moiré technology based fast method for the measurement of surface topography

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