Applied Sciences

Research

15 pages, 8588 KiB

Open AccessArticle

Development of Quick Three-Dimensional Shape Measurement Projection Mapping System Using a Whole-Space Tabulation Method

by Sodai Suzuki, Yuichi Akatsuka, Wei Jiang, Motoharu Fujigaki and Masaaki Otsu

Appl. Sci. 2019, 9(20), 4408; https://doi.org/10.3390/app9204408 - 18 Oct 2019

Cited by 3 | Viewed by 2710

Abstract

A grating projection method is often used as a highly accurate 3D shape measurement method. A real-time 3D shape measurement system can also be applied to measure a wide and smooth curved surface, such as in sheet metal processing. In this case, operators [...] Read more.

A grating projection method is often used as a highly accurate 3D shape measurement method. A real-time 3D shape measurement system can also be applied to measure a wide and smooth curved surface, such as in sheet metal processing. In this case, operators take much effort to recognize the positions of some problem areas on an object from a measured result displayed on a monitor. This study develops a projection mapping system projecting an evaluation image, such as height, displacement, gradient, curvature factor, and area of defect, onto an object. These evaluation results are obtained from the measured 3D shape. The evaluation image should be deformed according to the 3D shape of the object because the camera and projector positions are different. Therefore, this study proposes a method to quickly produce a deformed evaluation image using a whole-space tabulation method. A coordinate transform table allowed the conversion of a camera pixel coordinate into a projector pixel coordinate by using reference planes to apply deformation to the evaluation image according to the measured 3D shape. The quick coordinate transformation from a camera pixel coordinate into a projector pixel coordinate was realized using the coordinate transform table. This is a key idea of this study. It was confirmed that the coordinate transformation from the camera pixel coordinate to the projector coordinate could be performed in 4.5 ms using the coordinate transform table. In addition, 3D shape measurement projection mapping was applied to a curved sheet metal with small deformation, and the deformation part was clearly shown by projecting the height distribution. The architecture and the experimental results are shown herein. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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13 pages, 6278 KiB

Open AccessArticle

High Speed 3D Shape Measurement with Temporal Fourier Transform Profilometry

by Haihua Zhang, Qican Zhang, Yong Li and Yihang Liu

Appl. Sci. 2019, 9(19), 4123; https://doi.org/10.3390/app9194123 - 02 Oct 2019

Cited by 26 | Viewed by 4131

Abstract

A novel high-speed 3D shape measurement technology called temporal Fourier transform profilometry (TFTP for short) is proposed by combining the merits of Fourier transform profilometry (FTP) and phase-measuring profilometry (PMP). Instead of using the digital light projector, a mechanical projector is employed to [...] Read more.

A novel high-speed 3D shape measurement technology called temporal Fourier transform profilometry (TFTP for short) is proposed by combining the merits of Fourier transform profilometry (FTP) and phase-measuring profilometry (PMP). Instead of using the digital light projector, a mechanical projector is employed to generate multi-period phase-shifting fringe patterns sequentially. During the reconstruction process, the phase value of each pixel is calculated independently along the temporal axis and no spectrum filtering operation is performed in a spatial domain. Therefore, high-frequency components containing the detailed information of the measured object effectively remain. The proposed method is suitable for measuring isolated dynamic objects. Only one frame of deformed fringe pattern is required to retrieve one 3D shape of the measured object, so it has the obvious advantage if measuring the dynamic scene at a high speed. A low-cost self-made mechanical projector with fast projection speed is developed to execute the principle-proof experiments, whose results demonstrate the feasibility of measuring isolated dynamic objects. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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18 pages, 19065 KiB

Open AccessArticle

BICOS—An Algorithm for Fast Real-Time Correspondence Search for Statistical Pattern Projection-Based Active Stereo Sensors

by Patrick Dietrich, Stefan Heist, Martin Landmann, Peter Kühmstedt and Gunther Notni

Appl. Sci. 2019, 9(16), 3330; https://doi.org/10.3390/app9163330 - 14 Aug 2019

Cited by 14 | Viewed by 3142

Abstract

Pattern projection-based 3D measurement systems are widely used for contactless, non-destructive optical 3D shape measurements. In addition, many robot-operated automation tasks require real-time reconstruction of accurate 3D data. In previous works, we have demonstrated 3D scanning based on statistical pattern projection-aided stereo matching [...] Read more.

Pattern projection-based 3D measurement systems are widely used for contactless, non-destructive optical 3D shape measurements. In addition, many robot-operated automation tasks require real-time reconstruction of accurate 3D data. In previous works, we have demonstrated 3D scanning based on statistical pattern projection-aided stereo matching between two cameras. One major advantage of this technology is that the actually projected patterns do not have to be known a priori in the reconstruction software. This allows much simpler projector designs and enables high-speed projection. However, to find corresponding pixels between cameras, it is necessary to search the best match amongst all pixels within the geometrically possible image area (that is, within a range on the corresponding epipolar line). The well-established method for this search is to compare each candidate pixel by temporal normalized cross correlation of the brightness value sequences of both pixels. This is computationally expensive and interdicts fast real-time applications on inexpensive computer hardware. We show two variants of our algorithm “Binary Correspondence Search” (BICOS), which solve this task in significantly reduced calculation time. In practice, our algorithm is much faster than traditional, purely cross-correlation-based search while maintaining a similar level of accuracy. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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14 pages, 7169 KiB

Open AccessArticle

High-Speed Holographic Shape and Full-Field Displacement Measurements of the Tympanic Membrane in Normal and Experimentally Simulated Pathological Ears

by Haimi Tang, Payam Razavi, Koohyar Pooladvand, Pavel Psota, Nima Maftoon, John J. Rosowski, Cosme Furlong and Jeffrey T. Cheng

Appl. Sci. 2019, 9(14), 2809; https://doi.org/10.3390/app9142809 - 13 Jul 2019

Cited by 18 | Viewed by 3386

Abstract

To improve the understanding of the middle-ear hearing mechanism and assist in the diagnosis of middle-ear diseases, we are developing a high-speed digital holographic (HDH) system to measure the shape and acoustically-induced transient displacements of the tympanic membrane (TM). In this paper, we [...] Read more.

To improve the understanding of the middle-ear hearing mechanism and assist in the diagnosis of middle-ear diseases, we are developing a high-speed digital holographic (HDH) system to measure the shape and acoustically-induced transient displacements of the tympanic membrane (TM). In this paper, we performed measurements on cadaveric human ears with simulated common middle-ear pathologies. The frequency response function (FRF) of the normalized displacement by the stimulus (sound pressure) at each measured pixel point of the entire TM surface was calculated and the complex modal indicator function (CMIF) of the middle-ear system based on FRFs of the entire TM surface motions was used to differentiate different middle-ear pathologies. We also observed changes in the TM shape and the surface motion pattern before and after various middle-ear manipulations. The observations of distinguishable TM shapes and motion patterns in both time and frequency domains between normal and experimentally simulated pathological ears support the development of a quantitative clinical holography-based apparatus for diagnosing middle-ear pathologies. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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8 pages, 2377 KiB

Open AccessArticle

Demonstration of an Ultraprecise Optical Bench for the Taiji Space Gravitational Wave Detection Pathfinder Mission

by Yupeng Li, Heshan Liu, Ya Zhao, Wei Sha, Zhi Wang, Ziren Luo and Gang Jin

Appl. Sci. 2019, 9(10), 2087; https://doi.org/10.3390/app9102087 - 21 May 2019

Cited by 18 | Viewed by 2525

Abstract

For the Taiji space gravitational wave detection and its pathfinder mission, ultraprecise technology for optical assembly must be adopted to satisfy the high measurement sensitivities required. In this paper, we construct and evaluate an optical bench to assess its precision in optical assembly [...] Read more.

For the Taiji space gravitational wave detection and its pathfinder mission, ultraprecise technology for optical assembly must be adopted to satisfy the high measurement sensitivities required. In this paper, we construct and evaluate an optical bench to assess its precision in optical assembly and bonding. We opted for hydroxide-catalysis bonding technology and designed a corresponding adjustment scheme to achieve an ultraprecise assembly for the optical bench. After alignment, the angular deviation between the interference beam and its ideal position in the global coordinate system is no more than 45 μrad, and positional deviation is less than 10 μm. The final experimental results indicate that the measurement precision of the evaluated board is 6 pm/√Hz, which meets the specifications required for the Taiji pathfinder. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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15 pages, 3072 KiB

Open AccessArticle

Real-Time GPU-Based Digital Image Correlation Sensor for Marker-Free Strain-Controlled Fatigue Testing

by Andreas Blug, David Joel Regina, Stefan Eckmann, Melanie Senn, Alexander Bertz, Daniel Carl and Chris Eberl

Appl. Sci. 2019, 9(10), 2025; https://doi.org/10.3390/app9102025 - 16 May 2019

Cited by 18 | Viewed by 5194

Abstract

Digital image correlation (DIC) is a highly accurate image-based deformation measurement method achieving a repeatability in the range of

σ =

10⁻⁵ relative to the field-of-view. The method is well accepted in material testing for non-contact strain measurement. However, the [...] Read more.

Digital image correlation (DIC) is a highly accurate image-based deformation measurement method achieving a repeatability in the range of

σ =

10⁻⁵ relative to the field-of-view. The method is well accepted in material testing for non-contact strain measurement. However, the correlation makes it computationally slow on conventional, CPU-based computers. Recently, there have been DIC implementations based on graphics processing units (GPU) for strain-field evaluations with numerous templates per image at rather low image rates, but there are no real-time implementations for fast strain measurements with sampling rates above 1 kHz. In this article, a GPU-based 2D-DIC system is described achieving a strain sampling rate of 1.2 kHz with a latency of less than 2 milliseconds. In addition, the system uses the incidental, characteristic microstructure of the specimen surface for marker-free correlation, without need for any surface preparation—even on polished hourglass specimen. The system generates an elongation signal for standard PID-controllers of testing machines so that it directly replaces mechanical extensometers. Strain-controlled LCF measurements of steel, aluminum, and nickel-based superalloys at temperatures of up to 1000 °C are reported and the performance is compared to other path-dependent and path-independent DIC systems. According to our knowledge, this is one of the first GPU-based image processing systems for real-time closed-loop applications. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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15 pages, 8086 KiB

Open AccessArticle

Multi-Wavelength Digital-Phase-Shifting Moiré Based on Moiré Wavelength

by Fatemeh Mohammadi and Jonathan Kofman

Appl. Sci. 2019, 9(9), 1917; https://doi.org/10.3390/app9091917 - 09 May 2019

Cited by 9 | Viewed by 4444

Abstract

Multi-wavelength digital-phase-shifting moiré was demonstrated using multiple moiré wavelengths determined by system calibration over the full working depth. The method uses the extended noisy phase map as a reference to unwrap the phase map with a shorter wavelength, and thus achieve a less [...] Read more.

Multi-wavelength digital-phase-shifting moiré was demonstrated using multiple moiré wavelengths determined by system calibration over the full working depth. The method uses the extended noisy phase map as a reference to unwrap the phase map with a shorter wavelength, and thus achieve a less noisy and more accurate continuous phase map. The moiré wavelength calibration determines a moiré-wavelength to height relationship that permits pixelwise refinement of the moiré wavelength and height during 3D reconstruction. Only a single pattern has to be projected and, thus, a single image captured to compute each phase map with a different wavelength to perform digital-phase-shifting moiré temporal phase unwrapping. Only two captured images are required for two-wavelength phase unwrapping and three captured images for three-wavelength phase unwrapping. The method has been demonstrated in the 3D surface-shape measurement of an object with surface discontinuities and spatially isolated objects. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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12 pages, 4607 KiB

Open AccessArticle

3D Face Profilometry Based on Galvanometer Scanner with Infrared Fringe Projection in High Speed

by Junpeng Xue, Qican Zhang, Chenghang Li, Wei Lang, Min Wang and Yanfei Hu

Appl. Sci. 2019, 9(7), 1458; https://doi.org/10.3390/app9071458 - 07 Apr 2019

Cited by 35 | Viewed by 4781

Abstract

Structured light 3D shape metrology has become a very important technique and one of the hot research topics in 3D face recognition. However, it is still very challenging to use the digital light projector (DLP) in a 3D scanner and achieve high-speed, low-cost, [...] Read more.

Structured light 3D shape metrology has become a very important technique and one of the hot research topics in 3D face recognition. However, it is still very challenging to use the digital light projector (DLP) in a 3D scanner and achieve high-speed, low-cost, small-size, and infrared-illuminated measurements. Instead of using a DLP, this paper proposes to use a galvanometer scanner to project phase-shifted fringes with a projection speed of infrared fringes up to 500 fps. Moreover, the measurement accuracy of multi-frequency (hierarchical) and multi-wavelength (heterodyne) temporal phase unwrapping approaches implemented in this system is analyzed. The measurement accuracy of the two methods is better than 0.2 mm. Comparisons are made between this method and the classical DLP approach. This method can achieve a similar accuracy and repeatability compared to the classical DLP method when a face mask is measured. The experiments on real human face indicate that this proposed method can improve the field of 3D scanning applications at a lower cost. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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Graphical abstract

15 pages, 4224 KiB

Open AccessArticle

A Calibration Method for System Parameters in Direct Phase Measuring Deflectometry

by Xiaoting Deng, Nan Gao and Zonghua Zhang

Appl. Sci. 2019, 9(7), 1444; https://doi.org/10.3390/app9071444 - 06 Apr 2019

Cited by 3 | Viewed by 2746

Abstract

Phase measuring deflectometry has been widely studied as a way of obtaining the three-dimensional shape of specular objects. Recently, a new direct phase measuring deflectometry technique has been developed to measure the three-dimensional shape of specular objects that have discontinuous and/or isolated surfaces. [...] Read more.

Phase measuring deflectometry has been widely studied as a way of obtaining the three-dimensional shape of specular objects. Recently, a new direct phase measuring deflectometry technique has been developed to measure the three-dimensional shape of specular objects that have discontinuous and/or isolated surfaces. However, accurate calibration of the system parameters is an important step in direct phase measuring deflectometry. This paper proposes a new calibration method that uses phase information to obtain the system parameters. Phase data are used to accurately calibrate the relative orientation of two liquid crystal display screens in a camera coordinate system, by generating and displaying horizontal and vertical sinusoidal fringe patterns on the two screens. The results of the experiments with an artificial specular step and a concave mirror showed that the proposed calibration method can build a highly accurate relationship between the absolute phase map and the depth data. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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15 pages, 3061 KiB

Open AccessArticle

Dynamic Phase Measuring Profilometry Based on Tricolor Binary Fringe Encoding Combined Time-Division Multiplexing

by Guangkai Fu, Yiping Cao, Yapin Wang, Yingying Wan, Lu Wang and Chengmeng Li

Appl. Sci. 2019, 9(4), 813; https://doi.org/10.3390/app9040813 - 25 Feb 2019

Cited by 13 | Viewed by 4420

Abstract

A dynamic phase measuring profilometry (PMP) based on tricolor binary fringe combined time-division multiplexing principle is proposed. Only one tricolor binary fringe combined by red (R), green (G), and blue (B) binary fringes with the same fringe width but without any color overlapping [...] Read more.

A dynamic phase measuring profilometry (PMP) based on tricolor binary fringe combined time-division multiplexing principle is proposed. Only one tricolor binary fringe combined by red (R), green (G), and blue (B) binary fringes with the same fringe width but without any color overlapping one another is needed and sent into the flash memory of a high-speed digital light projector (HDLP) in advance. A specialized time-division multiplexing timing sequence is designed to control the HDLP to project the tricolor binary fringe saved in the flash memory onto the measured dynamic object separately and sequentially at 234 fps, at the same time, the projected light source mode is set as monochrome mode which means that all the RGB LEDs remain lighting. Meanwhile, it also triggers a high frame rate monochrome camera synchronized with the HDLP to capture the corresponding deformed patterns in R, G and B channels. By filtering, the nearly unbroken phase-shifting sinusoidal deformed patterns for three-step PMP can be extracted from the captured deformed patterns. It is equivalent to the three-dimensional (3D) shape reconstruction of the measured dynamic object at 78 fps. Experimental results verify the feasibility and the validity of the proposed method. It is effective for measuring the dynamic object and can avoid the color cross-talk effectively. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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15 pages, 6970 KiB

Open AccessArticle

Structural Low-Level Dynamic Response Analysis Using Deviations of Idealized Edge Profiles and Video Acceleration Magnification

by Dashan Zhang, Liangfei Fang, Ye Wei, Jie Guo and Bo Tian

Appl. Sci. 2019, 9(4), 712; https://doi.org/10.3390/app9040712 - 19 Feb 2019

Cited by 5 | Viewed by 2567

Abstract

The development of high-speed camera systems and image processing techniques has promoted the use of vision-based methods as a practical alternative for the analysis of non-contact structural dynamic responses. In this study, a deviation extraction method is introduced to obtain deviation signals from [...] Read more.

The development of high-speed camera systems and image processing techniques has promoted the use of vision-based methods as a practical alternative for the analysis of non-contact structural dynamic responses. In this study, a deviation extraction method is introduced to obtain deviation signals from structural idealized edge profiles. Given that the deviation temporal variations can reflect the structural vibration characteristics, a method based on singular-value decomposition (SVD) is proposed to extract valuable vibration signals from the matrix composed of deviations from all video frames. However, this method exhibits limitations when handling low-level motions that reflect high-frequency vibration components. Hence, a video acceleration magnification algorithm is employed to enhance low-level deviation variations before the extraction. The enhancement of low-level deviation variations is validated by a light-weight cantilever beam experiment and a noise barrier field test. From the extracted waveforms and their spectrums from the original and magnified videos, subtle deviations of the selected straight-line edge profiles are magnified in the reconstructed videos, and low-level high-frequency vibration signals are successfully enhanced in the final extraction results. Vibration characteristics of the test beam and the noise barrier are then analyzed using signals obtained by the proposed method. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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21 pages, 14011 KiB

Open AccessArticle

Extended Short-Time Fourier Transform for Ultrasonic Velocity Profiler on Two-Phase Bubbly Flow Using a Single Resonant Frequency

by Wongsakorn Wongsaroj, Ari Hamdani, Natee Thong-un, Hideharu Takahashi and Hiroshige Kikura

Appl. Sci. 2019, 9(1), 50; https://doi.org/10.3390/app9010050 - 24 Dec 2018

Cited by 22 | Viewed by 4685

Abstract

This study introduces a measurement technique for simultaneous phase-separated velocity in two-phase bubbly flow. The non-invasive technique, based on an Ultrasonic Velocity Profiler (UVP), is used in order to obtain an instantaneous, separate velocity profile for both liquid and bubble. The aim of [...] Read more.

This study introduces a measurement technique for simultaneous phase-separated velocity in two-phase bubbly flow. The non-invasive technique, based on an Ultrasonic Velocity Profiler (UVP), is used in order to obtain an instantaneous, separate velocity profile for both liquid and bubble. The aim of this paper is to measure each phase velocity at the same time and position it using only a single resonant frequency. To achieve this aim, extended signal processing of the Short-Time Fourier Transform (STFT) is proposed, combining with amplitude classification to analyze Doppler signal influenced from the bubbly flow. The use of developed algorithms allows the instantaneous separation of liquid and bubble velocity profiles. In this work, the developed technique is used to measure the velocity profile of bubbly flow in the vertical pipe, demonstrating the classification of liquid and bubble velocity. To confirm the accuracy of each velocity profile phase, the Particle Image Velocimetry (PIV) method is used for comparison. The results clarify that the proposed method is in good agreement with the PIV measurement. Finally, the effect of void fraction against velocity measurement of both phases was demonstrated. Full article

(This article belongs to the Special Issue High-speed Optical 3D Shape and Deformation Measurement)

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