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5 pages, 205 KiB

Open AccessEditorial

Special Issue on Precision Dimensional Measurements

by Kuang-Chao Fan and Liang-Chia Chen

Appl. Sci. 2019, 9(16), 3314; https://doi.org/10.3390/app9163314 - 12 Aug 2019

Cited by 1 | Viewed by 1972

Abstract

Precision dimensional measurements always play the critical role in workshop quality control [...] Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

Research

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13 pages, 10596 KiB

Open AccessArticle

A Structure for Accurately Determining the Mass and Center of Gravity of Rigid Bodies

by Meibao Wang, Xiaolin Zhang, Wenyan Tang and Jun Wang

Appl. Sci. 2019, 9(12), 2532; https://doi.org/10.3390/app9122532 - 21 Jun 2019

Cited by 16 | Viewed by 6592

Abstract

Measuring the mass and Center of Gravity (CG) of rigid bodies with a multi-point weighing method is widely used nowadays. Traditional methods usually include two parts with a certain location, i.e., a fixed platform and a mobile platform. In this paper, a novel [...] Read more.

Measuring the mass and Center of Gravity (CG) of rigid bodies with a multi-point weighing method is widely used nowadays. Traditional methods usually include two parts with a certain location, i.e., a fixed platform and a mobile platform. In this paper, a novel structure is proposed to adjust the mobile platform for eliminating side forces which may load on the load cells. In addition, closed-form equations are formulated to evaluate the performance of the structure, and transformation matrices are used to estimate the characteristics of the structure. Simulation results demonstrate that repeatability of the proposed structure is higher than the traditional one and there are no side forces. Moreover, the measurement results show that the relative error of mass was within 0.05%, and the error of CG was within ±0.3 mm. The structure presented in this paper provides a foundation for practical applications. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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14 pages, 5054 KiB

Open AccessArticle

Algorithm for Surfaces Profiles and Thickness Variation Measurement of a Transparent Plate Using a Fizeau Interferometer with Wavelength Tuning

by Tao Sun, Weiwei Zheng, Yingjie Yu, Ketao Yan, Anand Asundi and Sergiy Valukh

Appl. Sci. 2019, 9(11), 2349; https://doi.org/10.3390/app9112349 - 7 Jun 2019

Cited by 24 | Viewed by 3634

Abstract

An interferogram obtained from a transparent plate contains information on the profiles of both surfaces and on the thickness variation. The present work is devoted to the processing of interferograms of this type. The processing technique is based on a 36-step algorithm developed [...] Read more.

An interferogram obtained from a transparent plate contains information on the profiles of both surfaces and on the thickness variation. The present work is devoted to the processing of interferograms of this type. The processing technique is based on a 36-step algorithm developed by the authors for characterization of transparent plates having approximately equal reflections from both sides. The algorithm utilizes weighted multi-step phase shifting that enables one not only separately to extract the front and rear surface profiles together with the thickness variation of the tested plate but also to suppress the coupling errors between the higher harmonics and phase-shift deviation. The proposed measuring method was studied on a wavelength tunable Fizeau interferometer. The tested sample had an optical thickness and surface profile deviations equal to 0.51 µm, 1.38 µm and 0.89 µm, respectively. According to the results obtained using 10 repeated measurements, the root mean square (RMS) errors for determining both surface profiles did not exceed 1.5 nm. Experimental results show that the setup and presented 36-step algorithm are suitable for the measurement of a transparent plate of arbitrary thickness. Full article

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18 pages, 7550 KiB

Open AccessArticle

Optical 3-D Profilometry for Measuring Semiconductor Wafer Surfaces with Extremely Variant Reflectivities

by Liang-Chia Chen, Duc-Hieu Duong and Chin-Sheng Chen

Appl. Sci. 2019, 9(10), 2060; https://doi.org/10.3390/app9102060 - 19 May 2019

Cited by 11 | Viewed by 4601

Abstract

A new surface profilometry technique is proposed for profiling a wafer surface with both diffuse and specular reflective properties. Most moiré projection scanning techniques using triangulation principle work effectively on diffuse reflective surfaces, on which the reflected light beams are assumed to be [...] Read more.

A new surface profilometry technique is proposed for profiling a wafer surface with both diffuse and specular reflective properties. Most moiré projection scanning techniques using triangulation principle work effectively on diffuse reflective surfaces, on which the reflected light beams are assumed to be well captured by optical sensors. In reality, this assumption is no longer valid when measuring a semiconductor wafer surface having both diffuse and specular reflectivities. To resolve the above problem, the proposed technique uses a dual optical sensing configuration by engaging two optical sensors at two different viewing angles, with one acquiring diffuse reflective light and the other detecting at the same time specular surface light for achieving simultaneous full-field surface profilometry. The deformed fringes measured by both sensors could be further transformed into a 3-D profile and merged seamlessly for full-field surface reconstruction. Several calibration targets and industrial parts were measured to evaluate the feasibility and accuracy of the developed technique. Experimental results showed that the technique can effectively detect diffuse and specular light with repeatability of one standard deviation below 0.3 µm on a specular surface and 2.0 µm on a diffuse wafer surface when the vertical measuring range reaches 1.0 mm. The present findings indicate that the proposed technique is effective for 3-D microscale surface profilometry in in-situ semiconductor automated optical inspection (AOI). Full article

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20 pages, 9818 KiB

Open AccessArticle

An Accuracy-Efficiency-Power Consumption Hybrid Optimization Method for CNC Milling Process

by Shih-Ming Wang, Chun-Yi Lee, Hariyanto Gunawan and Chin-Cheng Yeh

Appl. Sci. 2019, 9(7), 1495; https://doi.org/10.3390/app9071495 - 10 Apr 2019

Cited by 13 | Viewed by 3949

Abstract

This study proposes a hybrid optimization method which can help users to find optimal cutting parameters which will provide better efficiency and lower power consumption for a milling process. Empirical models including performance-power consumption characteristic curves of servo motors were built, and an [...] Read more.

This study proposes a hybrid optimization method which can help users to find optimal cutting parameters which will provide better efficiency and lower power consumption for a milling process. Empirical models including performance-power consumption characteristic curves of servo motors were built, and an optimization algorithm adopting the empirical models with procedure guiding function was developed. The empirical models were built based on the measurements from planned machining experiments with different combination of machining parameters including spindle speed, feedrate, and chip load, etc. After integrating the models and algorithm, an optimization system with human machine interface, which has procedure guiding function, was developed. The system can recommend optimal machining parameters for a milling process for shorter machining time and lower electricity costs based on the original machining parameters. Finally, cutting experiments were conducted to verify the proposed system, and the results showed that the proposed method can effectively enhance efficiency by 42.06% and save 34.74% in machining costs through reducing machining time and electrical power consumption. Full article

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9 pages, 2401 KiB

Open AccessArticle

Compensation of Frequency Drift in Frequency-Sweep Polarization-Modulation Ranging System

by Shuyuan Gao, Rongyi Ji, Yao Li, Chun Liu, Junkai Shi, Yingling Pan and Weihu Zhou

Appl. Sci. 2019, 9(6), 1243; https://doi.org/10.3390/app9061243 - 25 Mar 2019

Cited by 4 | Viewed by 3086

Abstract

In frequency-sweep polarization-modulation ranging, distance is determined by the frequency of modulated waves and the corresponding wavelength multiple when emitted and returned waves are in phase. However, measurement of the frequency and the wavelength multiple is affected by thermally induced phase delay of [...] Read more.

In frequency-sweep polarization-modulation ranging, distance is determined by the frequency of modulated waves and the corresponding wavelength multiple when emitted and returned waves are in phase. However, measurement of the frequency and the wavelength multiple is affected by thermally induced phase delay of the polarized wave. In this article we systematically discuss the principle of the ranging method and analyze the influences of thermally induced phase delay. New approaches to measurement are proposed to eliminate the impact on frequency and the wavelength multiple. Theoretical analysis and experimental results proved the efficiency and applicability of the methods. Full article

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6 pages, 825 KiB

Open AccessArticle

Measurement Vertex Position of a Large Aspheric Mirror

by Jie Li, Fengtao Yan, Lin Chen, Jie Yang and Yongjian Wan

Appl. Sci. 2019, 9(6), 1038; https://doi.org/10.3390/app9061038 - 13 Mar 2019

Cited by 2 | Viewed by 2777

Abstract

We present a novel method to accurately measure the vertex position of a large aspheric mirror with a phasing measuring interferometer, a laser tracker, and a micro alignment telescope. The method consists of rotating the mirror by 180° about its mechanical axis and [...] Read more.

We present a novel method to accurately measure the vertex position of a large aspheric mirror with a phasing measuring interferometer, a laser tracker, and a micro alignment telescope. The method consists of rotating the mirror by 180° about its mechanical axis and measuring the change in displacement. Use of a micro alignment telescope eliminates the need to adjust the mirror during the measurement, eases the alignment of the testing system, and improves the vertex position measurement accuracy. Using this method, we measured the vertex position of an aspheric mirror 1 m in diameter and 2 m in radius of curvature. The vertex position measurement uncertainty is 88 μm. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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15 pages, 3886 KiB

Open AccessArticle

Characterization of Volume Gratings Based on Distributed Dielectric Constant Model Using Mueller Matrix Ellipsometry

by Hao Jiang, Zhao Ma, Honggang Gu, Xiuguo Chen and Shiyuan Liu

Appl. Sci. 2019, 9(4), 698; https://doi.org/10.3390/app9040698 - 18 Feb 2019

Cited by 7 | Viewed by 4036

Abstract

Volume grating is a key optical component due to its comprehensive applications. Other than the common grating structures, volume grating is essentially a predesigned refractive index distribution recorded in materials, which raises the challenges of metrology. Although we have demonstrated the potential application [...] Read more.

Volume grating is a key optical component due to its comprehensive applications. Other than the common grating structures, volume grating is essentially a predesigned refractive index distribution recorded in materials, which raises the challenges of metrology. Although we have demonstrated the potential application of ellipsometry for volume grating characterization, it has been limited due to the absence of general forward model reflecting the refractive index distribution. Herein, we introduced a distributed dielectric constant based rigorous coupled-wave analysis (RCWA) model to interpret the interaction between the incident light and volume grating, with which the Mueller matrix can be calculated. Combining with a regression analysis with the objective to match the measured Mueller matrices with minimum mean square error (MSE), the parameters of the dielectric constant distribution function can be determined. The proposed method has been demonstrated using a series of simulations of measuring the volume gratings with different dielectric constant distribution functions. Further demonstration has been carried out by experimental measurements on volume holographic gratings recorded in the composite of polymer and zinc sulfide (ZnS) nanoparticles. By directly fitting the spatiotemporal concentration of the nanoparticles, the diffusion coefficient has been further evaluated, which is consistent to the result reported in our previous investigations. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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19 pages, 12514 KiB

Open AccessArticle

A Geometric Error Measurement System for Linear Guideway Assembly and Calibration

by Tung-Hsien Hsieh, Po-Yu Chen, Wen-Yuh Jywe, Guan-Wu Chen and Ming-Shi Wang

Appl. Sci. 2019, 9(3), 574; https://doi.org/10.3390/app9030574 - 10 Feb 2019

Cited by 20 | Viewed by 4914

Abstract

Geometric errors, such as straightness, perpendicularity, and parallelism errors are determinant factors of both the accuracy and service life of a linear guideway. In this study, a multipurpose geometric error measurement system was mainly composed of a laser source and an in-lab-developed optical [...] Read more.

Geometric errors, such as straightness, perpendicularity, and parallelism errors are determinant factors of both the accuracy and service life of a linear guideway. In this study, a multipurpose geometric error measurement system was mainly composed of a laser source and an in-lab-developed optical module is proposed. Two adjustment methods were used for the in-lab-developed optical module to calibrate the altitude angle of the pentaprism: The first one is designed for ease of operation based on Michelson principle using a laser interferometer as the light receiver, and the second is aimed at high calibration repeatability based on the autocollimator principle using the quadrant detector (QD) to replace the light receiver. The result shows that the residual errors of the horizontal straightness and the vertical straightness are within ±1.3 µm and ±5.3 µm, respectively, when referred to as the commercial laser interferometer. Additionally, the residual errors of perpendicularity and parallelism are within ±1.2 µm and ±0.1 µm, respectively, when referred to as the granite reference blocks Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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14 pages, 12300 KiB

Open AccessArticle

A Method for Expansion of Z-Directional Measurement Range in a Mode-Locked Femtosecond Laser Chromatic Confocal Probe

by Chong Chen, Ryo Sato, Yuki Shimizu, Taku Nakamura, Hiraku Matsukuma and Wei Gao

Appl. Sci. 2019, 9(3), 454; https://doi.org/10.3390/app9030454 - 29 Jan 2019

Cited by 15 | Viewed by 3698

Abstract

A method is proposed to expand the Z-directional measurement range of a fiber-based dual-detector chromatic confocal probe with a mode-locked femtosecond laser source. In the dual-detector chromatic confocal probe, the Z-directional displacement of a measurement target is derived from the peak wavelength [...] Read more.

A method is proposed to expand the Z-directional measurement range of a fiber-based dual-detector chromatic confocal probe with a mode-locked femtosecond laser source. In the dual-detector chromatic confocal probe, the Z-directional displacement of a measurement target is derived from the peak wavelength in the normalized intensity ratio from the two light intensities obtained by the two identical fiber detectors. In this paper, a new method utilizing the main-lobe and side-lobes of axial responses acquired from both the normalized intensity ratio I_a and the invert normalized intensity ratio I_n, which is the inverse of I_a, is proposed to obtain the seamless relationship between the peak wavelength and the Z-directional displacement of a measurement target. Theoretical calculations and experimental investigation are carried out to demonstrate the feasibility of the proposed measurement range expansion method. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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11 pages, 4938 KiB

Open AccessArticle

Double-Diffracted Spatially Separated Heterodyne Grating Interferometer and Analysis on its Alignment Tolerance

by Di Chang, Xu Xing, Pengcheng Hu, Jianing Wang and Jiubin Tan

Appl. Sci. 2019, 9(2), 263; https://doi.org/10.3390/app9020263 - 13 Jan 2019

Cited by 13 | Viewed by 4428

Abstract

An optical configuration of double-diffracted spatially separated heterodyne grating interferometer with a mechanical fixture was designed. To further investigate its features and provide robust measurements, the alignment tolerance in double-diffracted spatially separated heterodyne grating interferometer was qualitatively and quantitatively analyzed. Except for the [...] Read more.

An optical configuration of double-diffracted spatially separated heterodyne grating interferometer with a mechanical fixture was designed. To further investigate its features and provide robust measurements, the alignment tolerance in double-diffracted spatially separated heterodyne grating interferometer was qualitatively and quantitatively analyzed. Except for the offset error causing no influence on the interfering signal, the effect of the other four errors, roll, yaw, pitch angles, and stand-off error were geometrically analyzed and mathematically modeled. The simulation result quantified the position mismatches of output beams in a double-diffracted configuration and found the crucial structural parameters related to the intensity of interfering signals. Experiments based on the grating interferometer with a mechanical fixture and the same optical configuration built by independent optical components were implemented, whose results agreed with the simulation. Besides, the results showed that the proposed grating interferometer structure could tolerate the ±1100 arcsec roll movement, ±440 arcsec yaw movement, ±280 arcsec pitch movement, and ±0.6 mm stand-off error when -10 dB intensity loss is afforded. Full article

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14 pages, 8552 KiB

Open AccessArticle

Ultraprecision Diameter Measurement of Small Holes with Large Depth-To-Diameter Ratios Based on Spherical Scattering Electrical-Field Probing

by Xingyuan Bian, Junning Cui, Yesheng Lu and Jiubin Tan

Appl. Sci. 2019, 9(2), 242; https://doi.org/10.3390/app9020242 - 10 Jan 2019

Cited by 15 | Viewed by 4710

Abstract

In order to solve the difficulty of precision measurement of small hole diameters with large depth-to-diameter ratios, a new measurement method based on spherical scattering electrical-field probing (SSEP) was developed. A spherical scattering electrical field with identical sensing characteristics in arbitrary spatial directions [...] Read more.

In order to solve the difficulty of precision measurement of small hole diameters with large depth-to-diameter ratios, a new measurement method based on spherical scattering electrical-field probing (SSEP) was developed. A spherical scattering electrical field with identical sensing characteristics in arbitrary spatial directions was formed to convert the micro gap between the probing-ball and the part being measured into an electrical signal. 3D non-contact probing, nanometer resolution, and approximate point probing—which are key properties for high measurement precision and large measurable depth-to-diameter ratios—were achieved. A specially designed hole diameter measuring machine (HDMM) was developed, and key techniques, including laser interferometry for macro displacement measurement of the probe, multi-degree-of-freedom adjustment of hole attitude, and measurement process planning, are described. Experiments were carried out using the HDMM and a probing sensor with a ϕ3-mm probing ball and a 150-mm-long stylus to verify the performance of the probing sensor and the measuring machine. The experimental results indicate that the resolution of the probing sensor was as small as 1 nm, and the expanded uncertainty of measurement result was 0.2 μm (k = 2) when a ϕ20-mm ring gauge standard was measured. Full article

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13 pages, 5432 KiB

Open AccessArticle

Dynamic Measurement Error Modeling and Analysis in a Photoelectric Scanning Measurement Network

by Shendong Shi, Linghui Yang, Jiarui Lin, Changyu Long, Rui Deng, Zhenyu Zhang and Jigui Zhu

Appl. Sci. 2019, 9(1), 62; https://doi.org/10.3390/app9010062 - 25 Dec 2018

Cited by 11 | Viewed by 3009

Abstract

A photoelectric scanning measurement network is a kind of distributed measurement system based on the principle of angle intersection, in which transmitters and photoelectric receivers are the main parts. The scanning lasers in transmitters emit signals and they are obtained by receivers at [...] Read more.

A photoelectric scanning measurement network is a kind of distributed measurement system based on the principle of angle intersection, in which transmitters and photoelectric receivers are the main parts. The scanning lasers in transmitters emit signals and they are obtained by receivers at the measured points. Then the coordinate of the receiver can be calculated by the optimization algorithm. Its outstanding static measurement performance and network scalability capacity give it great potential in large-scale metrology. However, when it comes to moving targets, the angle intersection failure will produce a dynamic error, which limits its further application. Nowadays the research on error modeling and compensation is also insufficient though it has been the crucial concern. In this paper, we analyzed error causes and constructed a dynamic error model. Dynamic error characteristics and the law of propagation were discussed. The measurement uncertainty at different movement speeds was quantized through simulation experiments. To verify the error model, experiments were designed and the dynamic error was evaluated in practice. It matched well with simulations. The model was tested to be reasonable, and provided theoretical support for error compensation. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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22 pages, 1783 KiB

Open AccessArticle

Evaluation and Optimization of Task-oriented Measurement Uncertainty for Coordinate Measuring Machines Based on Geometrical Product Specifications

by Yinbao Cheng, Zhongyu Wang, Xiaohuai Chen, Yaru Li, Hongyang Li, Hongli Li and Hanbin Wang

Appl. Sci. 2019, 9(1), 6; https://doi.org/10.3390/app9010006 - 20 Dec 2018

Cited by 27 | Viewed by 5104

Abstract

Measuring instruments are intended to be intelligent, precise, multi-functional and developing multidirectionally, scientific, and reasonable; the reliable evaluation of measurement uncertainty of precision instruments is also becoming more and more difficult, and the evaluation of the Coordinate Measuring Machines (CMM) measurement uncertainty is [...] Read more.

Measuring instruments are intended to be intelligent, precise, multi-functional and developing multidirectionally, scientific, and reasonable; the reliable evaluation of measurement uncertainty of precision instruments is also becoming more and more difficult, and the evaluation of the Coordinate Measuring Machines (CMM) measurement uncertainty is among the typical problems. Based on Geometric Product Specification (GPS), this paper has systematically studied the CMM uncertainty for evaluating the size and geometrical errors oriented toward measurement tasks, and thus has realized the rapid and reliable evaluation of the CMM uncertainty for task-oriented measurement. For overestimation of the CMM uncertainty for task-oriented measurements in the initial evaluation, a systematic optimization solution has been proposed. Finally, the feasibility and validity of the evaluation model and the optimization method have been verified by three different types of measurement examples of diameter, flatness and perpendicularity. It is typical and representative to systematically solve the problem of the CMM uncertainty for evaluating the measurement tasks targeted at dimensions and geometric errors, and the research contents can be effectively applied to solve the uncertainty evaluation problems of other precision instruments, which are of great practical significance not only for promoting the combination of modern uncertainty theory and practical applications but also for improving the application values of precision measurement instruments. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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19 pages, 4363 KiB

Open AccessArticle

A Novel Design of Through-Hole Depth On-Machine Optical Measuring Equipment for Automatic Drilling and Riveting

by Nianhan Wu, Wu Zhao, Xin Wang, Ye Tao and Zhengmeng Hou

Appl. Sci. 2018, 8(12), 2671; https://doi.org/10.3390/app8122671 - 18 Dec 2018

Cited by 4 | Viewed by 5387

Abstract

In the aerospace manufacturing industry, it is impossible to achieve precise and efficient automatic drilling and riveting for largescale composite board parts. The bottleneck is that the depth detection of rivet holes still relies on manual operation, which seriously affects the assembly efficiency [...] Read more.

In the aerospace manufacturing industry, it is impossible to achieve precise and efficient automatic drilling and riveting for largescale composite board parts. The bottleneck is that the depth detection of rivet holes still relies on manual operation, which seriously affects the assembly efficiency and stability of composite board parts. In order to realize accurate and efficient on-machine automatic measurement for through holes in the automatic drilling and riveting process of largescale composite board parts, this paper presents a novel hole depth measuring device. Its mechanical structure is developed based on our newly designed measurement scheme and optical path, the purpose of which is to convert the hole depth data into displacement data of the probe motion. Its electrical hardware consists of three units: a laser transceiver unit to pick up laser spots; a displacement measuring unit to capture the probe movement in real time; and a driving unit to achieve motion control of the probe. Finally, the experimental results indicated that the proposed method and device are capable of performing automatic measurements for through-hole depth. In addition, factors affecting the measuring accuracy and stability of the device are initially analyzed and discussed, which lay a foundation for subsequent research on error compensation and probe calibration. Full article

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12 pages, 2277 KiB

Open AccessArticle

Metrology of Nanostructures by Tomographic Mueller-Matrix Scatterometry

by Chao Chen, Xiuguo Chen, Yating Shi, Honggang Gu, Hao Jiang and Shiyuan Liu

Appl. Sci. 2018, 8(12), 2583; https://doi.org/10.3390/app8122583 - 12 Dec 2018

Cited by 9 | Viewed by 4061

Abstract

The development of necessary instrumentation and metrology at the nanoscale, especially fast, low-cost, and nondestructive metrology techniques, is of great significance for the realization of reliable and repeatable nanomanufacturing. In this work, we present the application of a homemade novel optical scatterometer called [...] Read more.

The development of necessary instrumentation and metrology at the nanoscale, especially fast, low-cost, and nondestructive metrology techniques, is of great significance for the realization of reliable and repeatable nanomanufacturing. In this work, we present the application of a homemade novel optical scatterometer called the tomographic Mueller-matrix scatterometer (TMS), for the measurement of photoresist gratings. The TMS adopts a dual rotating-compensator configuration and illuminates the nanostructure sequentially under test conditions by a plane wave, with varying illumination directions and records. For each illumination direction, the polarized scattered field along various directions of observation can be seen in the form of scattering Mueller matrices. That more scattering information is collected by TMS than conventional optical scatterometry ensures that it achieves better measurement sensitivity and accuracy. We also show the capability of TMS for determining both grating pitch and other structural parameters, which is incapable by current zeroth-order methods such as reflectometry- or ellipsometry-based scatterometry. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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23 pages, 8483 KiB

Open AccessArticle

Real-Time Tunnel Deformation Monitoring Technology Based on Laser and Machine Vision

by Zurong Qiu, Haopeng Li, Wenchuan Hu, Chenglin Wang, Jiachen Liu and Qianhui Sun

Appl. Sci. 2018, 8(12), 2579; https://doi.org/10.3390/app8122579 - 11 Dec 2018

Cited by 24 | Viewed by 5967

Abstract

Structural health monitoring is a topic of great concern in the world, and tunnel deformation monitoring is one of the important tasks. With the rapid developments in tunnel traffic infrastructure construction, engineers need a portable and real-time system to obtain the tunnel deformation [...] Read more.

Structural health monitoring is a topic of great concern in the world, and tunnel deformation monitoring is one of the important tasks. With the rapid developments in tunnel traffic infrastructure construction, engineers need a portable and real-time system to obtain the tunnel deformation during construction. This paper reports a novel method based on laser and machine vision to automatically measure tunnel deformation of multiple interest points in real time and effectively compensate for the environment vibration, and moreover it can overcome the influence of a dusty and dark tunnel environment in low visibility. An automatic and wireless real-time tunnel deformation monitoring system, which is based on laser and machine vision and can give early warnings for tunnel collapse accidents, is proposed. The proposed system uses a fixed laser beam as a monitoring reference. The image acquisition modules mounted on the measured points receive the laser spots and measure the tunnel accumulative deformation and instantaneous deformation velocity. Compensation methods are proposed to reduce measurement errors caused by laser beam feasibility, temperature, air refraction index, and wireless antenna attitude. The feasibility of the system is verified through tunnel tests. The accuracy of the detection system is better than 0.12 mm, the repeatability is less than 0.11 mm, and the minimum resolution is 10 μm; therefore, the proposed system is very suitable for real-time and automatic detection of tunnel deformation in low visibility during construction. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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18 pages, 5666 KiB

Open AccessArticle

Innovative Methodology of On-Line Point Cloud Data Compression for Free-Form Surface Scanning Measurement

by Yan Li, Yuyong Ma, Ye Tao and Zhengmeng Hou

Appl. Sci. 2018, 8(12), 2556; https://doi.org/10.3390/app8122556 - 10 Dec 2018

Cited by 2 | Viewed by 2898

Abstract

In order to obtain a highly accurate profile of a measured three-dimensional (3D) free-form surface, a scanning measuring device has to produce extremely dense point cloud data with a great sampling rate. Bottlenecks are created owing to inefficiencies in manipulating, storing and transferring [...] Read more.

In order to obtain a highly accurate profile of a measured three-dimensional (3D) free-form surface, a scanning measuring device has to produce extremely dense point cloud data with a great sampling rate. Bottlenecks are created owing to inefficiencies in manipulating, storing and transferring these data, and parametric modelling from them is quite time-consuming work. In order to effectively compress the dense point cloud data obtained from a 3D free-form surface during the real-time scanning measuring process, this paper presents an innovative methodology of an on-line point cloud data compression algorithm for 3D free-form surface scanning measurement. It has the ability to identify and eliminate data redundancy caused by geometric feature similarity between adjacent scanning layers. At first, the new algorithm adopts the bi-Akima method to compress the initial point cloud data; next, the data redundancy existing in the compressed point cloud is further identified and eliminated; then, we can get the final compressed point cloud data. Finally, the experiment is conducted, and the results demonstrate that the proposed algorithm is capable of obtaining high-quality data compression results with higher data compression ratios than other existing on-line point cloud data compression/reduction methods. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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15 pages, 8898 KiB

Open AccessArticle

Novel Boundary Edge Detection for Accurate 3D Surface Profilometry Using Digital Image Correlation

by Liang-Chia Chen and Ching-Wen Liang

Appl. Sci. 2018, 8(12), 2541; https://doi.org/10.3390/app8122541 - 7 Dec 2018

Cited by 3 | Viewed by 3903

Abstract

Digital image correlation (DIC) has emerged as a popular full-field surface profiling technique for analyzing both in-plane and out-of-plane dynamic structures. However, conventional DIC-based surface 3D profilometry often yields erroneous contours along surface edges. Boundary edge detection remains one of the key issues [...] Read more.

Digital image correlation (DIC) has emerged as a popular full-field surface profiling technique for analyzing both in-plane and out-of-plane dynamic structures. However, conventional DIC-based surface 3D profilometry often yields erroneous contours along surface edges. Boundary edge detection remains one of the key issues in DIC because a discontinuous surface edge cannot be detected due to optical diffraction and height ambiguity. To resolve the ambiguity of edge measurement in optical surface profilometry, this study develops a novel edge detection approach that incorporates a new algorithm using both the boundary subset and corner subset for accurate edge reconstruction. A pre-calibrated gauge block and a circle target were reconstructed to prove the feasibility of the proposed approach. Experiments on industrial objects with various surface reflective characteristics were also conducted. The results showed that the developed method achieved a 15-fold improvement in detection accuracy, with measurement error controlled within 1%. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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19 pages, 5819 KiB

Open AccessArticle

Uncertainty Evaluation for Measurements of Pitch Deviation and Out-of-Flatness of Planar Scale Gratings by a Fizeau Interferometer in Littrow Configuration

by Xin Xiong, Yuki Shimizu, Xiuguo Chen, Hiraku Matsukuma and Wei Gao

Appl. Sci. 2018, 8(12), 2539; https://doi.org/10.3390/app8122539 - 7 Dec 2018

Cited by 10 | Viewed by 4073

Abstract

Form errors of a planar scale grating, such as pitch deviations and out-of-flatness, are major contributors to the final measurement uncertainty of an interferential scanning-type planar encoder. Following the previous work, in which a method has been proposed to evaluate both the out-of-flatness [...] Read more.

Form errors of a planar scale grating, such as pitch deviations and out-of-flatness, are major contributors to the final measurement uncertainty of an interferential scanning-type planar encoder. Following the previous work, in which a method has been proposed to evaluate both the out-of-flatness and the pitch deviations of a planar scale grating by a Fizeau interferometer in Littrow configuration, uncertainty analysis on this method is performed in this paper. Theoretical equations are derived to make quantitative uncertainty analysis while taking possible error factors into account. To overcome the drawbacks of a traditional uncertainty matrix approach, a new procedure is proposed to evaluate the uncertainty in the PV (peak-to-valley) deviation of a surface form, so as to assure the quality of measurement. Experiments are finally conducted to demonstrate the feasibility of proposed uncertainty evaluation method. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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8 pages, 1837 KiB

Open AccessArticle

Design and Testing of a Compact Optical Prism Module for Multi-Degree-of-Freedom Grating Interferometry Application

by Xinghui Li, Yaping Shi, Xiang Xiao, Qian Zhou, Guanhao Wu, Haiou Lu and Kai Ni

Appl. Sci. 2018, 8(12), 2495; https://doi.org/10.3390/app8122495 - 4 Dec 2018

Cited by 17 | Viewed by 3673

Abstract

In this research, a key optical component for multi-degree-of-freedom (MDOF) surface encoder was designed, fabricated and evaluated. In a MDOF grating interferometry system, there are four diffraction beams from a two-axis scale grating and reference grating, respectively. For further modulation, these beams will [...] Read more.

In this research, a key optical component for multi-degree-of-freedom (MDOF) surface encoder was designed, fabricated and evaluated. In a MDOF grating interferometry system, there are four diffraction beams from a two-axis scale grating and reference grating, respectively. For further modulation, these beams will propagate more than 100 mm, which makes paralleling these beams necessary. In previous research, collimation lens, separate prisms and a home fabricated diffraction device by combining four separate one-axis line gratings in a glass substrate have been demonstrated. However, large power loss and assembly complicity makes these techniques less competitive. For solving this problem, this research proposed a new lens module, which is an improved type prism, quadrangular frustum pyramid (QFP) prism. The prism is designed in such a way that these four reflected beams from the grating are symmetrically incident into the prism through the upper surface, total reflected on the inner sides of the prism, and then parallel getting through the bottom surface. A prism that allows an incident beam diameter of 1 mm and four paralleling beams with a 10 mm distance between the two diffraction beams along one direction was designed, fabricated and tested. Testing results based on an entire grating interferometry system verified that the proposal in this research is greatly effective in beam paralleling in terms of less power loss and high paralleling and greatly reduces the assembly complicity, which will eventually be beneficial for grating interferometry application. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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9 pages, 2241 KiB

Open AccessArticle

Obtaining Vital Distances Using Wearable Inertial Measurement Unit for Real-Time, Biomechanical Feedback Training in Hammer-Throw

by Ye Wang, Hua Li, Bingjun Wan, Xiang Zhang and Gongbing Shan

Appl. Sci. 2018, 8(12), 2470; https://doi.org/10.3390/app8122470 - 3 Dec 2018

Cited by 14 | Viewed by 4097

Abstract

The hammer throw is one of the regular track and field competitions, but unlike other events, it has not seen a new world record for over three decades. The standstill may be caused by the lack of scientifically based training. In our previous [...] Read more.

The hammer throw is one of the regular track and field competitions, but unlike other events, it has not seen a new world record for over three decades. The standstill may be caused by the lack of scientifically based training. In our previous work, we have developed a wireless/wearable device for the wire tension measurement in order to develop real-time biomechanical feedback training. In this paper, we show the improvement of our wearable system by adding two sensors for tracking of two vital vertical distances. The paper describes the details related to the development of turning an inertial measurement unit into a tracking device for the dynamic distances. Our preliminary data has shown that the dynamic data of the hip and wrist could be used for revealing the coordination between the upper and the lower limbs during a throw. In conjunction with wearable wire-tension measurement, various motor control patterns employed for hammer throwing could be demystified. Such real-time information could be valuable for hammer-throw learning and optimization. Further studies are required to verify the potentials of the wearable system for its efficiency and effectiveness in coaching practice. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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7 pages, 1249 KiB

Open AccessArticle

Calculating the Effective Center Wavelength for Heterodyne Interferometry of an Optical Frequency Comb

by Shilin Xiong, Yue Wang, Yawen Cai, Jiuli Liu, Jie Liu and Guanhao Wu

Appl. Sci. 2018, 8(12), 2465; https://doi.org/10.3390/app8122465 - 3 Dec 2018

Cited by 6 | Viewed by 3311

Abstract

Heterodyne interferometry based on an optical frequency comb (OFC) is a powerful tool for distance measurement. In this paper, a method to calculate the effective center wavelength of wide spectrum heterodyne interference signal was explored though both simulation and experiment. Results showed that [...] Read more.

Heterodyne interferometry based on an optical frequency comb (OFC) is a powerful tool for distance measurement. In this paper, a method to calculate the effective center wavelength of wide spectrum heterodyne interference signal was explored though both simulation and experiment. Results showed that the effective center wavelength is a function of the spectra of the two interfered beams and time-delay of the two overlapped pulses. If the product of the spectra from two arms is symmetric, the effective center wavelength does not change with time-delay of the two pulses. The relative difference between the simulation and experiment was less than 0.06%. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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12 pages, 3756 KiB

Open AccessArticle

Selection of Optimal Path Control Algorithms for Probe Heads Used on Five-Axis Measuring Systems

by Adam Gąska, Piotr Gąska, Maciej Gruza and Jerzy Sładek

Appl. Sci. 2018, 8(12), 2455; https://doi.org/10.3390/app8122455 - 2 Dec 2018

Cited by 4 | Viewed by 2665

Abstract

The utilization of rotational movements of a probing system during points measurements
contributes to the reduction of measurement duration and increases measurement repeatability.
However, knowledge on such behavior and accuracy of probing systems is still unsatisfactory.
Machines combined with articulating probing systems that [...] Read more.

The utilization of rotational movements of a probing system during points measurements
contributes to the reduction of measurement duration and increases measurement repeatability.
However, knowledge on such behavior and accuracy of probing systems is still unsatisfactory.
Machines combined with articulating probing systems that have the ability of continuous indexation
become redundant systems, which means that the same points can be measured using almost infinite
mutual configurations of the machine and probe stylus orientations. Therefore, the proper selection
of inspection path planning method becomes one of the main factors affecting the accuracy of the
measurement. It is possible to assess the impact of this factor on the accuracy of the measurement
by comparing the results of the measurements of gauge elements, which are done using different
path controlling algorithms. After that, the best method for basic measuring tasks can be chosen
in order to reduce measurement errors. Measurements of the multi-feature check gauge, using the
default method for path planning and those chosen on the basis of described experiments, indicates
that the improvement of accuracy may reach several microns. Results presented in this paper can be
directly transferred to similar systems and measuring tasks, which are commonly met in industrial
and scientific practice. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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12 pages, 2810 KiB

Open AccessArticle

Demodulation Technique Based on Laser Interference for Weak Photo-Acoustic Signals on Water Surface

by Xiaolin Zhang, Hongjie Mao and Wenyan Tang

Appl. Sci. 2018, 8(12), 2423; https://doi.org/10.3390/app8122423 - 29 Nov 2018

Cited by 4 | Viewed by 3323

Abstract

To detect underwater sound-generating targets, a water surface acoustic wave laser interference and signal demodulation technique is proposed in this paper. The underlying principle of this technique involves casting a laser beam onto the water surface disturbed by an underwater acoustic source and [...] Read more.

To detect underwater sound-generating targets, a water surface acoustic wave laser interference and signal demodulation technique is proposed in this paper. The underlying principle of this technique involves casting a laser beam onto the water surface disturbed by an underwater acoustic source and creating interference between lights reflected by the surface and reference lights. A data acquisition and processing system was employed to obtain water surface acoustic wave information from the interference signals by means of demodulation, thus allowing detection of the underwater target. For the purpose of this study, an interference detection platform was set up in an optical dark chamber. High-frequency water surface fluctuations were introduced in the reference optical path as the phase generated carriers to create laser interference signals in two different paths, which received demodulation based on an improved arc tangent demodulation algorithm and characteristic ratio algorithm, respectively, in view of their different frequencies. Water surface wave information was then derived from such low-frequency and high-frequency signals. According to test results, in the frequency range of 200 Hz–10 kHz, the frequency detection accuracy was better than 1 Hz. The amplitude measurements exhibited high repeatability, with a standard deviation lower than 2.5 nm. The theory proposed in this paper is therefore experimentally verified with good results. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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11 pages, 5014 KiB

Open AccessArticle

A High Precision Capacitive Linear Displacement Sensor with Time-Grating that Provides Absolute Positioning Capability Based on a Vernier-Type Structure

by Xiaokang Liu, Hui Zhang, Kai Peng, Qifu Tang and Ziran Chen

Appl. Sci. 2018, 8(12), 2419; https://doi.org/10.3390/app8122419 - 28 Nov 2018

Cited by 14 | Viewed by 7649

Abstract

Nanometer-scale measurement devices with high accuracy and absolute long-range positioning capability are increasingly demanded in the field of computer numerical control machining. To meet this demand, the present report proposes a capacitive absolute linear displacement sensor with time-grating that employs a vernier-type structure [...] Read more.

Nanometer-scale measurement devices with high accuracy and absolute long-range positioning capability are increasingly demanded in the field of computer numerical control machining. To meet this demand, the present report proposes a capacitive absolute linear displacement sensor with time-grating that employs a vernier-type structure based on a previously proposed single-row capacitive sensing structure. The novel proposed vernier-type absolute time-grating (VATG) sensor employs two capacitor rows, each with an equivalent measurement range. The first capacitor row is designed with n periods to realize fine measurement, while the second capacitor row is designed with n − 1 periods, and the phase difference between the second row and the first row is employed to obtain absolute positioning information. A prototype VATG sensor with a total measurement range of 600 mm and n = 150 is fabricated using printed circuit board manufacturing technology, and its measurement performance is evaluated experimentally. Harmonic analysis demonstrates that the measurement error mainly consists of first-harmonic error, which is mostly caused by signal crosstalk. Accordingly, an optimized prototype VATG sensor is fabricated by adding a shielding layer between the two capacitor rows and designing a differential induction structure. Experimental results demonstrate that the measurement error of the optimized prototype sensor is ±1.25 μm over the full 600 mm range and ±0.25 μm over a single 4 mm period. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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9 pages, 2296 KiB

Open AccessArticle

Metrology Data-Based Simulation of Freeform Optics

by Ingo Sieber, Allen Y. Yi and Ulrich Gengenbach

Appl. Sci. 2018, 8(12), 2338; https://doi.org/10.3390/app8122338 - 22 Nov 2018

Cited by 6 | Viewed by 3698

Abstract

This paper describes the approach to use measurement data to enhance the simulation model for designing freeform optics. Design for manufacturing of freeform optics is still challenging, since the classical tolerancing procedures cannot be applied. In the case of spherical optics manufacturing, tolerances [...] Read more.

This paper describes the approach to use measurement data to enhance the simulation model for designing freeform optics. Design for manufacturing of freeform optics is still challenging, since the classical tolerancing procedures cannot be applied. In the case of spherical optics manufacturing, tolerances are more or less isotropic, and this relationship is lost in case of freeform surfaces. Hence, an accurate performance prediction of the manufactured optics cannot be made. To make the modeling approach as accurate as possible, integration of measured surface data of fabricated freeform optics in the modeling environment is proposed. This approach enables performance prediction of the real manufactured freeform surfaces as well as optimization of the manufacturing process. In our case study this approach is used on the design of an Alvarez-optics manufactured using a microinjection molding (µIM) process. The parameters of the µIM process are optimized on the basis of simulation analysis resulting in optics, with a performance very close to the nominal design. Measurement of the freeform surfaces is conducted using a tactile surface measurement tool. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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13 pages, 4219 KiB

Open AccessArticle

Experimental Analyses on Multiscale Structural and Mechanical Properties of ε-Si/GeSi/C-Si Materials

by Wei Qiu, Lu-Lu Ma, Hong-Tao Wang, Ren-Rong Liang, Yu-Cheng Zhao and Yun-Shen Zhou

Appl. Sci. 2018, 8(12), 2333; https://doi.org/10.3390/app8122333 - 22 Nov 2018

Cited by 5 | Viewed by 3859

Abstract

Strained silicon (ε-Si) is a promising material that could extend Moore’s law by enhancing electron mobility. A ε-Si material is usually composed of multiscale, multilayer heterostructures, where the strained-silicon film or strap is tens-of-nanometers thick, and its buffer layers are of the micrometer [...] Read more.

Strained silicon (ε-Si) is a promising material that could extend Moore’s law by enhancing electron mobility. A ε-Si material is usually composed of multiscale, multilayer heterostructures, where the strained-silicon film or strap is tens-of-nanometers thick, and its buffer layers are of the micrometer scale. The structural properties determine the electrical performance and reliability of ε-Si-based devices. Inhomogeneous residual stress is induced during the preparation, which induces ε-Si structure failure. In this work, biaxial strained-silicon films that contain graded and relaxed germanium-silicon buffer layers were prepared on monocrystalline silicon wafers through reduced-pressure chemical-vapor epitaxy. The layer components and thicknesses were measured using energy-dispersive spectroscopy and scanning-electron microscopy. Crystal and lattice characters were observed by using high-resolution transmission-electron microscopy and micro-Raman spectroscopy. The residual stress distribution along cross-sections of the ε-Si multilayer structures was examined by using micro-Raman mapping. The experimental results showed that, with a gradual increase in germanium concentration, the increasing residual stress was suppressed owing to dislocation networks and dislocation loops inside the buffer layers, which favored the practical application. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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7 pages, 3503 KiB

Open AccessArticle

A Real-Time Measurement Method of Air Refractive Index Based on Special Material Etalon

by Guo-Ying Ren, Xing-Hua Qu and Shuang Ding

Appl. Sci. 2018, 8(11), 2325; https://doi.org/10.3390/app8112325 - 21 Nov 2018

Cited by 3 | Viewed by 3473

Abstract

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not [...] Read more.

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not easy to realize in practical work because of its complex measurement principle and the huge volume of the measurement device; while the measurement accuracy and speed based on the indirect method cannot adapt to the real-time, fast and accurate measurement requirements of industrially changing environments, resulting in distortion of the results. In this study, a measurement method of the refractive index of air based on a special material etalon is proposed. The method enables rapid and direct measurement of the air refractive index when the environment changes and it is given the realization process. Finally, the experimental results show that the deviation between this method and the modified Edlen formula is about 2.5 × 10⁻⁷, and that this method can quickly reflect the changes of the environment, which prove the correctness of this method and its ability manage rapid environmental responses. This method is worth popularizing in industrial measurement. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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11 pages, 5948 KiB

Open AccessArticle

An Orthogonal Type Two-Axis Lloyd’s Mirror for Holographic Fabrication of Two-Dimensional Planar Scale Gratings with Large Area

by Xinghui Li, Haiou Lu, Qian Zhou, Guanhao Wu, Kai Ni and Xiaohao Wang

Appl. Sci. 2018, 8(11), 2283; https://doi.org/10.3390/app8112283 - 19 Nov 2018

Cited by 28 | Viewed by 4321

Abstract

In this paper, an orthogonal type two-axis Lloyd’s mirror interference lithography technique was employed to fabricate two-dimensional planar scale gratings for surface encoder application. The two-axis Lloyd’s mirror interferometer is composed of a substrate and two reflective mirrors (X- and Y-mirrors), which are [...] Read more.

In this paper, an orthogonal type two-axis Lloyd’s mirror interference lithography technique was employed to fabricate two-dimensional planar scale gratings for surface encoder application. The two-axis Lloyd’s mirror interferometer is composed of a substrate and two reflective mirrors (X- and Y-mirrors), which are placed edge by edge perpendicularly. An expanded and collimated beam was divided into three beams by this interferometer, a direct beam and two reflected beams, projected onto the substrate, X- and Y-mirrors, respectively. The unexpected beam sections having twice reflected off the mirrors were blocked by a filter. The remaining two reflected beams interfered with the direct beam on the substrate, generating perpendicularly cross patterns thus forming two-dimensional scale gratings. However, the two reflected beams undesirably interfere with each other and generate a grating pattern along 45-degree direction against the two orthogonal direction, which influence the pattern uniformity. Though an undesired grating pattern can be eliminated by polarization modulation with introduction of waveplates, spatial configuration of waveplates inevitably downsized the eventual grating, which is a key parameter for grating interferometry application. For solving this problem, theoretical and experimental study was carefully carried out to evaluate the fabrication quality with and without polarization modulation. Two-dimensional scale gratings with a 1 μm period in X- and Y-directions were achieved by using the constructed experiment system with a 442 nm He-Cd laser source. Atomic force microscopy (AFM) images and the result of diffraction performances demonstrated that the orthogonal type two-axis Lloyd’s mirror interferometer can stand a small order undesired interference, that is, a degree of orthogonality between two reflected beams, denoted by γ, no larger than a nominal value of 0.1. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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11 pages, 2379 KiB

Open AccessArticle

Simultaneous Measurement Method and Error Analysis of the Six Degrees-of-Freedom Motion Errors of a Rotary Axis

by Chuanchen Bao, Qibo Feng and Jiakun Li

Appl. Sci. 2018, 8(11), 2232; https://doi.org/10.3390/app8112232 - 13 Nov 2018

Cited by 13 | Viewed by 2830

Abstract

Error measurement of a rotary axis is the key to error compensation and to improving motion accuracy. However, only a few instruments can measure all the motion errors of a rotary axis. In this paper, a device based on laser collimation and laser [...] Read more.

Error measurement of a rotary axis is the key to error compensation and to improving motion accuracy. However, only a few instruments can measure all the motion errors of a rotary axis. In this paper, a device based on laser collimation and laser interferometry was introduced for simultaneous measurement of all six degrees-of-freedom motion errors of a rotary axis. Synchronous rotation of the target and reference rotary axes was achieved by developing a proportional–integral–derivative algorithm. An error model for the measuring device was established using a homogeneous transformation matrix. The influences of installation errors, manufacturing errors, and error crosstalk were studied in detail, and compensation methods for them were proposed. After compensation, the repeatability of axial and radial motion errors was significantly improved. The repeatability values of angular positioning error and of tilt motion error around the y axis and x axis were 28.0″, 2.8″, and 3.9″. The repeatability values of translational motion errors were less than 2.8 μm. The comparison experiments show that the comparison errors of angular positioning error and tilt motion error around the y axis were 2.3″ and 2.9″, respectively. These results demonstrate the effectiveness of our method and the error compensation model. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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14 pages, 6826 KiB

Open AccessArticle

Development of a Compact Three-Degree-of-Freedom Laser Measurement System with Self-Wavelength Correction for Displacement Feedback of a Nanopositioning Stage

by Yindi Cai, Zhifeng Lou, Siying Ling, Bo-syun Liao and Kuang-chao Fan

Appl. Sci. 2018, 8(11), 2209; https://doi.org/10.3390/app8112209 - 10 Nov 2018

Cited by 19 | Viewed by 4168

Abstract

This paper presents a miniature three-degree-of-freedom laser measurement (3DOFLM) system for displacement feedback and error compensation of a nanopositioning stage. The 3DOFLM system is composed of a miniature Michelson interferometer (MMI) kit, a wavelength corrector kit, and a miniature autocollimator kit. A low-cost [...] Read more.

This paper presents a miniature three-degree-of-freedom laser measurement (3DOFLM) system for displacement feedback and error compensation of a nanopositioning stage. The 3DOFLM system is composed of a miniature Michelson interferometer (MMI) kit, a wavelength corrector kit, and a miniature autocollimator kit. A low-cost laser diode is employed as the laser source. The motion of the stage can cause an optical path difference in the MMI kit so as to produce interference fringes. The interference signals with a phase interval of 90° due to the phase control are detected by four photodetectors. The wavelength corrector kit, based on the grating diffraction principle and the autocollimation principle, provides real-time correction of the laser diode wavelength, which is the length unit of the MMI kit. The miniature autocollimator kit based on the autocollimation principle is employed to measure angular errors and compensate induced Abbe error of the moving table. The developed 3DOFLM system was constructed with dimensions of 80 mm (x) × 90 mm (y) × 20 mm (z) so that it could be embedded into the nanopositioning stage. A series of calibration and comparison experiments were carried out to test the performance of this system. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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19 pages, 15660 KiB

Open AccessArticle

Sub-Pixel Chessboard Corner Localization for Camera Calibration and Pose Estimation

by Tianlong Yang, Qiancheng Zhao, Xian Wang and Quan Zhou

Appl. Sci. 2018, 8(11), 2118; https://doi.org/10.3390/app8112118 - 1 Nov 2018

Cited by 16 | Viewed by 7754

Abstract

This work describes a novel approach to localize sub-pixel chessboard corners for camera calibration and pose estimation. An ideally continuous chessboard corner model is established, as a function of corner coordinates, rotation and shear angles, gain and offset of grayscale, and blurring strength. [...] Read more.

This work describes a novel approach to localize sub-pixel chessboard corners for camera calibration and pose estimation. An ideally continuous chessboard corner model is established, as a function of corner coordinates, rotation and shear angles, gain and offset of grayscale, and blurring strength. The ideal model is evaluated by a low-cost and high-similarity approximation for sub-pixel localization, and by performing a nonlinear fit to input image. A self-checking technique is also proposed by investigating qualities of the model fits, for ensuring the reliability of addressing perspective-n-point problem. The proposed method is verified by experiments, and results show that it can share a high performance. It is also implemented and examined in a common vision system, which demonstrates that it is suitable for on-site use. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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12 pages, 3412 KiB

Open AccessArticle

Measurement of High Numerical Aperture Cylindrical Surface with Iterative Stitching Algorithm

by Dingfu Chen, Junzheng Peng, Sergiy Valyukh, Anand Asundi and Yingjie Yu

Appl. Sci. 2018, 8(11), 2092; https://doi.org/10.3390/app8112092 - 29 Oct 2018

Cited by 16 | Viewed by 3515

Abstract

There are some limitations in null test measurements in stitching interferometry. In order to meet the null test conditions, the moving distance between the sub-apertures often deviates from the theoretical preset distance, which leads to a position deviation of sub-apertures when measured. To [...] Read more.

There are some limitations in null test measurements in stitching interferometry. In order to meet the null test conditions, the moving distance between the sub-apertures often deviates from the theoretical preset distance, which leads to a position deviation of sub-apertures when measured. To overcome this problem, an algorithm for data processing is proposed in this paper. An optimal estimation of the deviation between sub-apertures is used to update their positions, and then a new overlapped region is obtained and again optimized. This process is repeated until the algorithm converges to an acceptable tolerance, and finally exact stitching is realized. A cylindrical lens was taken as an object for experimental examination of the proposed method. The obtained results demonstrate the validity, reliability, and feasibility of our iterative stitching algorithm. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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13 pages, 4719 KiB

Open AccessArticle

Error Correction for FSI-Based System without Cooperative Target Using an Adaptive Filtering Method and a Phase-Matching Mosaic Algorithm

by Xing-Ting Xiong, Xing-Hua Qu and Fu-Min Zhang

Appl. Sci. 2018, 8(10), 1954; https://doi.org/10.3390/app8101954 - 17 Oct 2018

Cited by 5 | Viewed by 2879

Abstract

In our frequency scanning interferometry-based (FSI-based) absolute distance measurement system, a frequency sampling method is used to eliminate the influence of laser tuning nonlinearity. However, because the external cavity laser (ECL) has been used for five years, factors such as the mode hopping [...] Read more.

In our frequency scanning interferometry-based (FSI-based) absolute distance measurement system, a frequency sampling method is used to eliminate the influence of laser tuning nonlinearity. However, because the external cavity laser (ECL) has been used for five years, factors such as the mode hopping of the ECL and the low signal-to-noise ratio (SNR) in a non-cooperative target measurement bring new problems, including erroneous sampling points, phase jumps, and interfering signals. This article analyzes the impacts of the erroneous sampling points and interfering signals on the accuracy of measurement, and then proposes an adaptive filtering method to eliminate the influence. In addition, a phase-matching mosaic algorithm is used to eliminate the phase jump, and a segmentation mosaic algorithm is used to improve the data processing speed. The result of the simulation proves the efficiency of our method. In experiments, the measured target was located at eight different positions on a precise guide rail, and the incident angle was 12 degrees. The maximum deviation of the measured results between the FSI-based system and the He-Ne interferometer was 9.6 μm, and the maximum mean square error of our method was 2.4 μm, which approached the Cramer-Rao lower bound (CRLB) of 0.8 μm. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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12 pages, 6329 KiB

Open AccessArticle

Influence of Illumination Polarization and Target Structure on Measurement Sensitivity of Through-Focus Scanning Optical Microscopy

by Yufu Qu, Renju Peng, Jialin Hao, Hui Pan, Jiebin Niu and Jie Jiang

Appl. Sci. 2018, 8(10), 1819; https://doi.org/10.3390/app8101819 - 3 Oct 2018

Cited by 4 | Viewed by 4452

Abstract

Unlike the optical information taken from a single in-focus image of general optical microscopy, through-focus scanning optical microscopy (TSOM) involves scanning a target through the focus and capturing of a series of images. These images can be used to conduct three-dimensional inspection and [...] Read more.

Unlike the optical information taken from a single in-focus image of general optical microscopy, through-focus scanning optical microscopy (TSOM) involves scanning a target through the focus and capturing of a series of images. These images can be used to conduct three-dimensional inspection and metrology with nanometer-scale lateral and vertical sensitivity. The sensitivity of TSOM strongly depends on many mechanical and optical factors. In this study, how illumination polarization and target structure affect the sensitivity of TSOM is analyzed. Firstly, the complete imaging procedure of the polarized light is investigated. Secondly, through-focus scanning results of different targets with two illumination polarizations are simulated using the finite-difference time-domain method. Thirdly, a few experiments are performed to verify the influence of illumination polarization and target structures on the sensitivity of TSOM. Both the results of the simulation and experiments illustrate an apparent influence of polarization on the sensitivity of inspecting the targets with center asymmetric structures. For enhanced sensitivity, illumination polarization should be perpendicular to the target texture. This conclusion is meaningful to adjust illumination polarization purposefully for different structure characteristics and improve the sensitivity of metrology. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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15 pages, 9032 KiB

Open AccessArticle

Design, Measurement and Shape Reconstruction of Soft Surgical Actuator Based on Fiber Bragg Gratings

by Yanlin He, Lianqing Zhu, Guangkai Sun, Mingxin Yu and Mingli Dong

Appl. Sci. 2018, 8(10), 1773; https://doi.org/10.3390/app8101773 - 30 Sep 2018

Cited by 28 | Viewed by 5090

Abstract

Soft actuators are the components responsible for organs and tissues adsorptive fixation in some surgical operations, but the lack of shape sensing and monitoring of a soft actuator greatly limits their application potential. Consequently, this paper proposes a real-time 3D shape reconstruction method [...] Read more.

Soft actuators are the components responsible for organs and tissues adsorptive fixation in some surgical operations, but the lack of shape sensing and monitoring of a soft actuator greatly limits their application potential. Consequently, this paper proposes a real-time 3D shape reconstruction method of soft surgical actuator which has an embedded optical fiber with two Fiber Bragg Grating (FBG) sensors. First, the design principle and the sensing of the soft actuator based on FBG sensors are analyzed, and the fabrication process of soft actuator which has an embedded optical fiber with two FBG sensors is described. Next, the calibration of the FBG sensors is conducted. Based on curvatures and curve fitting functions, the strategy of 3D shapes reconstruction of the soft actuator is presented. Finally, some bending experiments of the soft actuator are carried out, and the 3D shapes of the soft actuator at different bending states are reconstructed. This well reconstructed 3D shape of a soft actuator demonstrates the effectiveness of the shape reconstruction method that is proposed in this paper, as well as the potential and increased applications of these structures for real soft surgical actuators. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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15 pages, 5180 KiB

Open AccessArticle

Precision Manufacturing of Patterned Beryllium Bronze Leaf Springs via Chemical Etching

by Rui-Jun Li, Peng-Yu Wang, Dan-Dong Li, Kuang-Chao Fan, Fang-Fang Liu, Li-Juan Chen and Qiang-Xian Huang

Appl. Sci. 2018, 8(9), 1476; https://doi.org/10.3390/app8091476 - 28 Aug 2018

Cited by 8 | Viewed by 4512

Abstract

Patterned leaf springs made of a beryllium bronze sheet are the key components of certain micro/nano contact probes. The accuracy of the probe is determined based on the precision of the formed pattern. However, a traditional manufacturing method using wire-electrode discharge machining (wire-EDM) [...] Read more.

Patterned leaf springs made of a beryllium bronze sheet are the key components of certain micro/nano contact probes. The accuracy of the probe is determined based on the precision of the formed pattern. However, a traditional manufacturing method using wire-electrode discharge machining (wire-EDM) is subject to poor tolerance at the sharp edges and corners. In addition, high energy consumption and costs are incurred for complex patterns. This paper presents a new chemical etching method for the manufacturing of a patterned leaf spring with high precision. Both the principle and process are introduced. Taguchi experiments were designed and conducted and the optimal process parameters were obtained based on the mean value and a variance analysis. Four V-shaped and some other complex patterned leaf springs were successfully fabricated. Comparison experiments concerning the characteristic parameters of the leaf spring were also conducted. The experimental results reveal that the patterned leaf springs manufactured through this method are much better than those achieved using wire-EDM. This manufacturing method can be used to fabricate different high-precision patterned leaf springs or membranes for coordinate measuring machines (CMM) probes and other measuring equipment. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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13 pages, 3850 KiB

Open AccessArticle

Calibration Method of Orthogonally Splitting Imaging Pose Sensor Based on General Imaging Model

by Na Zhao, Changku Sun and Peng Wang

Appl. Sci. 2018, 8(8), 1399; https://doi.org/10.3390/app8081399 - 19 Aug 2018

Cited by 2 | Viewed by 3672

Abstract

Orthogonally splitting imaging pose sensor is a new sensor with two orthogonal line array charge coupled devices (CCDs). Owing to its special structure, there are distortion correction and imaging model problems during the calibration procedure. This paper proposes a calibration method based on [...] Read more.

Orthogonally splitting imaging pose sensor is a new sensor with two orthogonal line array charge coupled devices (CCDs). Owing to its special structure, there are distortion correction and imaging model problems during the calibration procedure. This paper proposes a calibration method based on the general imaging model to solve these problems. The method introduces Plücker Coordinate to describe the mapping relation between the image coordinate system and the world coordinate system. This paper solves the mapping relation with radial basis function interpolation and adaptively selecting control points with Kmeans clustering method to improve the fitting accuracy. This paper determines the appropriate radial basis function and its shape parameter by experiments. And these parameters are used to calibrate the orthogonally splitting imaging pose sensor. According to the calibration result, the root mean square (RMS)of calibration dataset and the RMS of test dataset are 0.048 mm and 0.049 mm. A comparative experiment is conducted between the pinhole imaging model and the general imaging model. Experimental results show that the calibration method based on general imaging model applies to the orthogonally splitting imaging pose sensor. The calibration method requires only one image corresponding to the target in the world coordinates and distortion correction is not required to be taken into account. Compared with the calibration method based on the pinhole imaging model, the calibration procedure based on the general imaging model is easier and accuracy is greater. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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15 pages, 6470 KiB

Open AccessArticle

Non-Contact and Real-Time Measurement of Kolsky Bar with Temporal Speckle Interferometry

by Shanwei Yang, Zhan Gao, Haihui Ruan, Chenjia Gao, Xu Wang, Xiang Sun and Xin Wen

Appl. Sci. 2018, 8(5), 808; https://doi.org/10.3390/app8050808 - 17 May 2018

Cited by 6 | Viewed by 3325

Abstract

In this paper, a new non-contact and real-time measurement system for Kolsky bars is presented. This system uses two sets of temporal speckle interferometry in-plane displacement measurement devices to replace two strain gauges of conventional Kolsky bars. The in-plane displacement measurement of the [...] Read more.

In this paper, a new non-contact and real-time measurement system for Kolsky bars is presented. This system uses two sets of temporal speckle interferometry in-plane displacement measurement devices to replace two strain gauges of conventional Kolsky bars. The in-plane displacement measurement of the Kolsky bar is mainly intended to provide a new test method for the dynamic mechanical properties of small-size material samples with diameters below 2 mm. This method is non-contact, does not require any intermediate medium, and can make the Kolsky bar applicable to characterizing the dynamic mechanical properties of materials under higher strain rates and smaller size conditions. The measuring devices and principles are described. In addition, a preliminary experiment is carried out to demonstrate the performance of this new device. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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Review

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27 pages, 9702 KiB

Open AccessReview

Frequency-Shifted Optical Feedback Measurement Technologies Using a Solid-State Microchip Laser

by Kaiyi Zhu, Hongfang Chen, Shulian Zhang, Zhaoyao Shi, Yun Wang and Yidong Tan

Appl. Sci. 2019, 9(1), 109; https://doi.org/10.3390/app9010109 - 29 Dec 2018

Cited by 26 | Viewed by 5016

Abstract

Since its first application toward displacement measurements in the early-1960s, laser feedback interferometry has become a fast-developing precision measurement modality with many kinds of lasers. By employing the frequency-shifted optical feedback, microchip laser feedback interferometry has been widely researched due to its advantages [...] Read more.

Since its first application toward displacement measurements in the early-1960s, laser feedback interferometry has become a fast-developing precision measurement modality with many kinds of lasers. By employing the frequency-shifted optical feedback, microchip laser feedback interferometry has been widely researched due to its advantages of high sensitivity, simple structure, and easy alignment. More recently, the laser confocal feedback tomography has been proposed, which combines the high sensitivity of laser frequency-shifted feedback effect and the axial positioning ability of confocal microscopy. In this paper, the principles of a laser frequency-shifted optical feedback interferometer and laser confocal feedback tomography are briefly introduced. Then we describe their applications in various kinds of metrology regarding displacement measurement, vibration measurement, physical quantities measurement, imaging, profilometry, microstructure measurement, and so on. Finally, the existing challenges and promising future directions are discussed. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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Other

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20 pages, 6478 KiB

Open AccessTechnical Note

Comparison of Current Five-Point Cylindricity Error Separation Techniques

by Wenwen Liu, Penghao Hu and Kuangchao Fan

Appl. Sci. 2018, 8(10), 1946; https://doi.org/10.3390/app8101946 - 16 Oct 2018

Cited by 8 | Viewed by 4099

Abstract

Cylindricity is a kind of three-dimensional form distortion of a cylinder. An accurate in situ measurement of cylindricity is relatively complex because measuring and reconstructing cylindrical profile and evaluating out-of-cylindricity should be involved. Any method of in situ measuring cylindricity must solve a [...] Read more.

Cylindricity is a kind of three-dimensional form distortion of a cylinder. An accurate in situ measurement of cylindricity is relatively complex because measuring and reconstructing cylindrical profile and evaluating out-of-cylindricity should be involved. Any method of in situ measuring cylindricity must solve a common issue, i.e., to eliminate spindle error motions and carriage error motions during measurement and reconstruction. Thus, error separation techniques have played an important role in in situ cylindricity measurement through multipoint detections. Although several valuable five-point methods for in situ measurement of cylindrical profile have been proposed up to present, namely the parallel scan, spiral scan, and V-block scan, there are obvious differences in many aspects, such as the arrangement of probes, error separation model, reconstruction method, adaptability to service environment, accuracy and reliability in practical application, etc. This paper presents the evaluation of their advantages and disadvantages in theory and the actual measurement based on the standard ISO 12180. Suggestions for best meeting the requirements of modern manufacturing and the most prospective one for industrial applications are also given. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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