Computer-generated moiré profilometry based on fringe-superposition

Abstract A computer-generated moiré profilometry based on algebraic addition instead of algebraic multiplication is proposed. Firstly, the two AC components of the captured fringe patterns on the reference plane with $$\pi /2$$ π / 2 phase difference are retrieved and saved in advance. While measuring, two sinusoidal gratings with $$\pi$$ π phase difference are projected onto the measured object alternatively, and the corresponding deformed patterns are captured. Then the AC component of the captured deformed pattern can be separated exactly. When the positive and negative AC component of the captured deformed pattern are added to the two prestored AC components respectively, two moiré fringes only reflect sine and cosine of the object’s phase information can be successfully generated via a series of data processing procedures. Finally, the phase distribution of the measured object can be extracted by arctangent of the ratio of these two moiré fringes. Compared with computer-generated moiré profilometry based on algebraic multiplication, this proposed method can reduce the effect of high frequency noise and residual DC component on measurement and improve the measurement accuracy. While compared with $$\pi$$ π phase shifting FTP, this method can measure more complex objects with better measurement capability. Experimental results verify the feasibility and validity of the proposed method.

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Color-encoded single-shot computer-generated Moiré profilometry

Scientific Reports ◽

10.1038/s41598-021-90522-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hechen Zhang ◽

Yiping Cao ◽

Chengmeng Li ◽

Lu Wang ◽

Hongmei Li ◽

...

Keyword(s):

Real Time ◽

Phase Difference ◽

Reference Plane ◽

Single Shot ◽

3D Measurement ◽

Measured Object ◽

Moiré Fringes ◽

Sinusoidal Gratings ◽

Fringe Patterns ◽

Object Relative

AbstractA color-encoded single-shot computer-generated Moiré profilometry (CSCGMP) is proposed. Two sinusoidal gratings with a π phase difference are encoded in red and blue channels respectively to combine a composite color grating. While this composite color grating is projected onto the measured object, the corresponding color deformed pattern can be captured. So two deformed patterns with a π phase difference are separated from its red and blue components respectively. After normalization and subtraction, the AC component of both separated deformed patterns can be extracted. If this AC component respectively multiplied by the two AC components of fringe patterns of reference plane with a π/2 phase difference prepared and saved on the computer in advance, two computer-generated Moiré fringes just respectively standing for sine and cosine of phase which is modulated by the height of the object relative to the reference plane are figured out. So the 3D shape of the measured object can be reconstructed with normal computer-generated Moiré profilometry. Both simulation and experimental results show the feasibility and validity of the proposed method. It has potential in real-time 3D measurement due to its single-shot feature.

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Microshape Measurement Method Using Speckle Interferometry Based on Phase Analysis

Photonics ◽

10.3390/photonics8040112 ◽

2021 ◽

Vol 8 (4) ◽

pp. 112

Author(s):

Yasuhiko Arai

Keyword(s):

Fine Structure ◽

Phase Analysis ◽

Measurement Method ◽

Phase Distribution ◽

Periodic Structures ◽

Scattered Light ◽

Speckle Interferometry ◽

Diffraction Limit ◽

Silica Microspheres ◽

Measured Object

A method for the measurement of the shape of a fine structure beyond the diffraction limit based on speckle interferometry has been reported. In this paper, the mechanism for measuring the shape of the fine structure in speckle interferometry using scattered light as the illumination light is discussed. Furthermore, by analyzing the phase distribution of the scattered light from the surface of the measured object, this method can be used to measure the shapes of periodic structures and single silica microspheres beyond the diffraction limit.

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Theoretical study of the properties of X-ray diffraction moiré fringes. II. Illustration of angularly integrated moiré images

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273319004601 ◽

2019 ◽

Vol 75 (4) ◽

pp. 610-623

Author(s):

Jun-ichi Yoshimura

Keyword(s):

Incident Wave ◽

Angular Width ◽

X Ray Diffraction ◽

Experimental Conditions ◽

Acta Cryst ◽

Low Contrast ◽

X Ray ◽

Moiré Fringes ◽

Wide Range ◽

Fringe Patterns

Using a theory of X-ray diffraction moiré fringes developed in a previous paper, labelled Part I [Yoshimura (2015). Acta Cryst. A71, 368–381], the X-ray moiré images of a silicon bicrystal having a weak curvature strain and an interspacing gap, assumed to be integrated for an incident-wave angular width, are simulation-computed over a wide range of crystal thicknesses and incident-wave angular width, likely under practical experimental conditions. Along with the simulated moiré images, the graphs of characteristic quantities on the moiré images are presented for a full understanding of them. The treated moiré images are all of rotation moiré. Mo Kα1 radiation and the 220 reflection were assumed in the simulation. The results of this simulation show that fringe patterns, which are significantly modified from simple straight fringes of rotation moiré, appear in some ranges of crystal thicknesses and incident-wave angular width, due to a combined effect of Pendellösung oscillation and an added phase difference from the interspacing gap, under the presence of a curvature strain. The moiré fringes which slope to the perpendicular direction to the diffraction vector in spite of the assumed condition of rotation moiré, and fringe patterns where low-contrast bands are produced with a sharp bend of fringes arising along the bands are examples of the modified fringe pattern. This simulation study provides a wide theoretical survey of the type of bicrystal moiré image produced under a particular condition.

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Real-time phase distribution analysis of fringe patterns

10.1117/12.323330 ◽

1998 ◽

Cited By ~ 3

Author(s):

Yoshiharu Morimoto ◽

Motoharu Fujigaki

Keyword(s):

Real Time ◽

Phase Distribution ◽

Distribution Analysis ◽

Fringe Patterns

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Statistical Modeling of the Patches DC Component for Low-Frequency Noise Reduction

2019 27th European Signal Processing Conference (EUSIPCO) ◽

10.23919/eusipco.2019.8903131 ◽

2019 ◽

Author(s):

Antoine Houdard

Keyword(s):

Noise Reduction ◽

Statistical Modeling ◽

Low Frequency ◽

Frequency Noise ◽

Low Frequency Noise ◽

Dc Component

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Analysis of moiré patterns in images of thin YBa2Cu3O7-δ films on MgO

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121582 ◽

1992 ◽

Vol 50 (1) ◽

pp. 236-237

Author(s):

M. Grant Norton ◽

C. Barry Carter

Keyword(s):

Metal Films ◽

Double Diffraction ◽

Bright Field ◽

Small Deviations ◽

Moiré Fringes ◽

Moire Patterns ◽

Interfacial Strain ◽

Fringe Patterns ◽

Moiré Patterns ◽

Scattered Beam

Moiré fringes arise from the interference between diffracted beams from two overlapping crystals (double diffraction) and in the bright-field case the forward scattered beam. The fringe patterns act as magnifiers of lattice imperfections and small deviations from perfect crystallographic orientation and symmetry. Moiré patterns have been used previously to study, for example, the growth of metal films on substrates such as molybdenum disulfide—which can easily be prepared to electron transparency. Moiré patterns can be used to identify microstructural defects in epitactic deposits. For example, the presence of rotationally misaligned grains, the presence of dislocations, and residual interfacial strain will be revealed in the fringe pattern.

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Pressure Measurement and Pattern Recognition by Using Neural Networks

Dynamic Systems and Control, Parts A and B ◽

10.1115/imece2005-79745 ◽

2005 ◽

Author(s):

Parham Piroozan

Keyword(s):

Neural Network ◽

Neural Networks ◽

Control System ◽

Pressure Sensor ◽

Back Propagation ◽

Back Propagation Neural Network ◽

Moiré Fringes ◽

Flexible Wall ◽

Four Levels ◽

Fringe Patterns

This paper describes an intelligent control system that uses electro-optics and neural networks to control the flow of air over a flexible wall. In this investigation a pressure sensor which was part of the wall of the wind tunnel and an optical apparatus were used to produce moire´ fringes. A back propagation neural network was used to analyze the fringe patterns and to classify the pressures into four levels. A second neural network was used to recognize the pressure patterns and to provide the input to a control system that was capable of modifying the shape of the flexible wall in order to preserve the stability of the flow. The flexible wall was part of the wall of the wind tunnel and was installed in the upstream of the flow. It was made of silicone rubber and had an area of 76 mm by 76 mm. There were 15 rows of actuators installed under the flexible wall which were used to change the shape of the wall. In the downstream of the flow was an optical pressure sensor which had the same dimensions as the flexible wall and consisted of a 15 × 15 array of small diaphragms. These diaphragms responded to the pressure fluctuations in the boundary layer flow and were the source of the signals for the optical system. A CCD camera viewed the pressure sensor through an optical apparatus which produced moire´ fringes. A back propagation neural network analyzed the fringe patterns and classified the pressures into four levels. The classified pressures which was a 15 × 15 array of numbers ranging from 1 to 4 was the input to a second back propagation neural network which was used to recognize the pressure patterns. The output from the back propagation neural network used for pattern recognition provided the input to a control system that changed the shape of the flexible wall. This paper presents the experimental results as well as the computer simulations which were created for this project. This includes the complete process of creating the slope fringes, classifying the pressures into four levels, recognizing the wall pressure patterns and generating the output signals to the actuator for changing the shape of the flexible wall.

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Transition to Measure Synchronization in Coupled Hamiltonian Systems

International Journal of Modern Physics B ◽

10.1142/s021797920302243x ◽

2003 ◽

Vol 17 (22n24) ◽

pp. 4349-4354

Author(s):

Xingang Wang ◽

Gang Hu ◽

Kai Hu ◽

C.-H. Lai

Keyword(s):

Random Walk ◽

Hamiltonian Systems ◽

Phase Difference ◽

Phase Distribution ◽

Phase Locking ◽

Scaling Relationship ◽

Measure Synchronization ◽

Relationship Of ◽

Synchronized Region

The transition to measure synchronization in two coupled φ4 equations are investigated numerically both for quasiperiodic and chaotic cases. Quantities like the bare energy and phase difference are employed to study the underlying behaviors during this process. For transition between quasiperiodic states, the distribution of phase difference tends to concentrate at large angles before measure synchronization, and is confined to within a certain range after measure synchronization. For transition between quasiperiodicity and chaos, phase locking is not achieved and a random-walk-like behavior of the phase difference is found in the measure synchronized region. The scaling relationship of the phase distribution and the behavior of the bare energy are also discussed.

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