This thesis addresses the issues existing in traditional laser tracking displacement measurement technology in the field of ultraprecision metrology by designing a differential signal processing circuit for high-preci...This thesis addresses the issues existing in traditional laser tracking displacement measurement technology in the field of ultraprecision metrology by designing a differential signal processing circuit for high-precision laser interferometric displacement measurement.A stable power supply module is designed to provide low-noise voltage to the entire circuit.An analog circuit system is constructed,including key circuits such as photoelectric sensors,I-V amplification,zero adjustment,fully differential amplification,and amplitude modulation filtering.To acquire and process signals,the PMAC Acc24E3 data acquisition card is selected,which realizes phase demodulation through reversible square wave counting,inverts displacement information,and a visual interface for the host computer is designed.Experimental verification shows that the designed system achieves micrometer-level measurement accuracy within a range of 0-10mm,with a maximum measurement error of less than 1.2μm,a maximum measurement speed of 6m/s,and a resolution better than 0.158μm.展开更多
To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizi...To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring.展开更多
Three dimensional（3D） displacements, which can be translated further into 3D strain, are key parameters tor design, manufacturing and quality control. Using different optical setups, phase-shift methods, and algorit...Three dimensional（3D） displacements, which can be translated further into 3D strain, are key parameters tor design, manufacturing and quality control. Using different optical setups, phase-shift methods, and algorithms, several different 3D electronic speckle pattern interferometry（ESPl） systems for displacement and strain measurements have been achieved and commercialized. This paper provides a review of the recent developments in ESPI systems for 3D displacement and strain measurement. After an overview of the fundamentals of ESP! theory, temporal phase-shift, and spatial phase-shift techniques, 3D deformation measurements by the temporal phase-shift ESPI system, which is suited well for static measurement, and by the spatial phase-shift ESPI system, which is particularly useful for dynamic measurement, are discussed. For each method, the basic theory, a brief derivation and different optical layouts are presented. The state of art application, potential and limitation of the ESPI systems are shown and demonstrated.展开更多
The effectiveness of monitoring and early-warning systems for ground deformation phenomena,such as sinkholes,depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deforma...The effectiveness of monitoring and early-warning systems for ground deformation phenomena,such as sinkholes,depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deformation preceding catastrophic failures.Sagging sinkholes with a slow subsidence rate and diffuse edges pose a significant challenge for subsidence monitoring due to the low deformation rates and limited lateral strain gradients.In this work,we satisfactorily illustrate the practicality of the Brillouin optical time domain analysis(BOTDA)to measure the spatial-temporal patterns of the vertical displacement in such challenging slow-moving sagging sinkholes.To assess the performance of the approach,we compare the strain recorded by the distributed optical fiber sensor with the vertical displacement measured by high-precision leveling.The results show a good spatial correlation with the ability to identify the maximum subsidence point.There is also a good temporal correlation with the detection of an acceleration phase in the subsidence associated with a flood event.展开更多
We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. An...We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. Another Fabry-Perot interferometer is used to obtain the key initial angle of incidence.展开更多
A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the chang...A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate.By accumulating the number of quarters in each direction and the specific position in the final quarter,the large-scale measurement is fulfilled.Displacements in Xand Y-direction can be measured independently and simultaneously.Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity.Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm.An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed.The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.展开更多
In this paper, a sinusoidal phase-modulating Fabry-Perot interferometer is proposed to measure angular displacement. The usefulness of the interferometer is demonstrated by simulations and experiments.
This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement...This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system are described. The experimental results of thermal displacement of an electronic device are shown.展开更多
In this Letter,we propose a simple structure of an orthogonal type double Michelson interferometer.The orthogonal detection method overcomes the problems of uneven ranging sensitivity and the inability of traditional ...In this Letter,we propose a simple structure of an orthogonal type double Michelson interferometer.The orthogonal detection method overcomes the problems of uneven ranging sensitivity and the inability of traditional interferometers to determine the displacement direction.The displacement measurement principle and signal processing method of the orthogonal double interferometer are studied.Unlike the arctangent algorithm,the displacement analysis uses the arc cosine algorithm,avoiding any pole limit in the distance analysis process.The minimum step size of the final experimental displacement system is 5 nm,which exhibits good repeatability,and the average error is less than 0.12 nm.展开更多
The auditory system of mammals enables the perception of sound from our surrounding world.Containing some of the smallest bones in the body,the ear transduces complex acoustic signals with high-temporal sensitivity to...The auditory system of mammals enables the perception of sound from our surrounding world.Containing some of the smallest bones in the body,the ear transduces complex acoustic signals with high-temporal sensitivity to complex mechanical vibrations with magnitudes as small as tens of picometers.Measurements of the shape and acoustically induced motions of different components of the ear are essential if we are to expand our understanding of hearing mechanisms,and also provide quantitative information for the development of numerical ear models that can be used to improve hearing protection,clinical diagnosis,and repair of damaged or diseased ears.We are developing digital holographic methods and instrumentation using an ultra-high speed camera to measure shape and acoustically-induced motions in the middle ear.Specifically we study the eardrum,the first structure of the middle ear which initializes the acoustic-mechanical transduction of sound for hearing.Our measurement system is capable of performing holographic measurement at rates up to 2.1 M frames per second.Two shape measurement modalities had previously been implemented into our holographic systems:(1)a multi-wavelength method with a wavelength tunable laser;and(2)a multi-angle illumination method with a single wavelength laser.In this paper,we present a third method using a miniaturized fringe projection system with a microelectromechanical system(MEMS)mirror.Further,we optimize the processing of large data sets of holographic displacement measurements using a vectorized Pearson's correlation algorithm.We validate and compare the shape and displacement measurements of our methodologies using a National Institute of Standards and Technology(NIST)traceable gauge and sound-activated latex membranes and human eardrums.展开更多
Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement trans...Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.展开更多
A signal processing method of realizing a large-range displacement measurement in a sinusoidal phase- modulating laser diode interferometer is proposed. The method of obtaining the dynamic value of the effective sinus...A signal processing method of realizing a large-range displacement measurement in a sinusoidal phase- modulating laser diode interferometer is proposed. The method of obtaining the dynamic value of the effective sinusoidal phase-modulating depth is detailed, and the residual amplitude modulation is also taken into account. Numerical simulations and experiments are carried out to compare this method with the traditional one. We prove that, with this method, the sinusoidal phase-modulating laser diode interferometer can realize a centimeter-level displacement measurement range with high precision, which is much better than the traditional method.展开更多
Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic...Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.展开更多
The sampling Moiré(SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. I...The sampling Moiré(SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. In this review, the basic principle of the SM method for measuring the twodimensional displacement and strain distributions is introduced. When the grid is not a standard orthogonal grating and cracks exist on the specimen surface, the measurement methods are also stated. Two of the most typical application examples are described in detail. One is the dynamic deflection measurement of a large-scale concrete bridge, and the other is the residual thermal strain measurement of small-scale flip chip packages. Several further development points of this method are pointed out. The SM method is expected to be used for deformation measurement of various structures and materials for residual stress evaluation, crack location prediction, and crack growth evaluation on broad scales.展开更多
Three-dimensional(3D)microdisplacement monitoring plays a crucial role in the assembly of large aircraft.This paper presents a broadly applicable high-precision online 3D microdisplacement monitoring method and system...Three-dimensional(3D)microdisplacement monitoring plays a crucial role in the assembly of large aircraft.This paper presents a broadly applicable high-precision online 3D microdisplacement monitoring method and system based on proximity sensors as well as a corresponding in situ calibration method,which can be applied under various extreme working conditions encountered in the aircraft assembly process,such as compact and obstructed spaces.A 3D monitoring model is first established to achieve 3D microdisplacement monitoring based only on the one-dimensional distances measured by proximity sensors,which concerns the extrinsic sensor parameters,such as the probe base point(PBP)and the unit displacement vector(UDV).Then,a calibration method is employed to obtain these extrinsic parameters with high precision by combining spatial transformation principles and weighted optimization.Finally,calibration and monitoring experiments performed for a tailplane assembly process are reported.The calibration precision for the PBP is better than±10 lm in the X and Y directions and±2 lm in the Z direction,and the calibration precision for the UDV is better than 0.07°.Moreover,the accuracy of the 3D microdisplacement monitoring system can reach±15 lm.In general,this paper provides new insights into the modeling and calibration of 3D microdisplacement monitoring based on proximity sensors and a precise,efficient,and low-cost technical means for performing related measurements in compact spaces during the aircraft assembly process.展开更多
Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dy...Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dynamic displacement is then usually obtained indirectly from the double integration of the acceleration data.This paper reports an experimental method of measuring the displacement of stayed cables using a digital video camera.With the newly developed videogrammetric technique,the video clips are transferred into image frames,from which the shape and location of the target are identified.The displacement time history is then captured.The technique is applied to a cable-stayed bridge to measure the dynamic displacement of stay cables.The displacement is compared with the acceleration data in the frequency and time domains.The results show that the displacement measured by the digital video camera is comparable to the counterparts integrated from the acceleration data.The vibration frequencies identified from the acceleration are finally used to estimate the tension forces of the cables.The results show that the tension forces have insignificant changes after one year’s operation.展开更多
In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring meth...In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on.展开更多
Based on laser-scanned measuring technology, a met ho d of on-line dynamic non-contact measurement and feedback control of processin g dimension, i.e. the double edges laser-scanned large diameter on-line dynami c mea...Based on laser-scanned measuring technology, a met ho d of on-line dynamic non-contact measurement and feedback control of processin g dimension, i.e. the double edges laser-scanned large diameter on-line dynami c measurement and control system is presented, which can be used to measure diam eter in large-scale machine part processing. In this paper, the working princip le, overall structure and microcomputer real-time control and data processing s ystem of the system are discussed in detail, the method of double edges scanned large diameter dimension measurement and control is theoretically analyzed, its possibility has been verified by experiments of lathing large diameters machine parts by a vertical lathe. The system adopts the measuring scheme of double edge s laser-scanned combined with grating displacement measurement. The two edges c haracteristic information of the measured diameter is given by the double edges laser-scanned measuring system, the non-contact measurement of large diameter dimension is realized to combine with the grating displacement measuring systems . The main controller gives out feedback control signal by means of measured res ults, and controls advance and retreat of lathe tool by the servo-control syste m of a vertical lathe to realize on-line dynamic non-contact measurement and c ontrol in processing.展开更多
In this paper,a new direct optical triangulation(DOT) for measuring theout-of-plane displacement is given.In order to state its principle,DOT is used to measure a micro-displacement of a rigid body,and at the same tim...In this paper,a new direct optical triangulation(DOT) for measuring theout-of-plane displacement is given.In order to state its principle,DOT is used to measure a micro-displacement of a rigid body,and at the same time,the method of digital image processing is also given.展开更多
This paper presents experiment results of the measurement conducted at the Roznew Dam power plant. For a course of starting and operating of turbo-plants, downstream face of the dam was monitored in relation to its ev...This paper presents experiment results of the measurement conducted at the Roznew Dam power plant. For a course of starting and operating of turbo-plants, downstream face of the dam was monitored in relation to its eventual displacements on direction parallel to the construction axis. For the purpose of the experiment, geodetic measurement techniques and 2D DIC （digital image correlation） method （utilizing photographs of the object recorded with digital camera） were compared with regard to credibility, efficiency and accuracy. The vertical and horizontal displacements were monitored by tachometers measurements. The deformations in x-axis and y-axis on the wall surface was monitored by 2D DIC. It has been noticed that 2D DIC method is a surface method, continuous--not discreet. It allows for continuous observations of surface deformations, which is not possible in case of tachemetric measurements. Despite many advantages, the 2D DIC method lacks unambiguous evaluation of precision and relevance of designated displacements, which is rather significant for possibilities of utilization in technical control of large engineered objects. It should be also marked that the tachometric method is more reliable but is more laborious. Research of this type might comprise additional element for the assessment of the influence of dynamic loads, such as activating turbine water flow, onto the overall condition of the surveyed structure.展开更多
文摘This thesis addresses the issues existing in traditional laser tracking displacement measurement technology in the field of ultraprecision metrology by designing a differential signal processing circuit for high-precision laser interferometric displacement measurement.A stable power supply module is designed to provide low-noise voltage to the entire circuit.An analog circuit system is constructed,including key circuits such as photoelectric sensors,I-V amplification,zero adjustment,fully differential amplification,and amplitude modulation filtering.To acquire and process signals,the PMAC Acc24E3 data acquisition card is selected,which realizes phase demodulation through reversible square wave counting,inverts displacement information,and a visual interface for the host computer is designed.Experimental verification shows that the designed system achieves micrometer-level measurement accuracy within a range of 0-10mm,with a maximum measurement error of less than 1.2μm,a maximum measurement speed of 6m/s,and a resolution better than 0.158μm.
文摘To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring.
基金supported by National Natural Science Foundation of China(Grant Nos.51275054,51075116)
文摘Three dimensional（3D） displacements, which can be translated further into 3D strain, are key parameters tor design, manufacturing and quality control. Using different optical setups, phase-shift methods, and algorithms, several different 3D electronic speckle pattern interferometry（ESPl） systems for displacement and strain measurements have been achieved and commercialized. This paper provides a review of the recent developments in ESPI systems for 3D displacement and strain measurement. After an overview of the fundamentals of ESP! theory, temporal phase-shift, and spatial phase-shift techniques, 3D deformation measurements by the temporal phase-shift ESPI system, which is suited well for static measurement, and by the spatial phase-shift ESPI system, which is particularly useful for dynamic measurement, are discussed. For each method, the basic theory, a brief derivation and different optical layouts are presented. The state of art application, potential and limitation of the ESPI systems are shown and demonstrated.
基金This work has been supported by Ministerio de Ciencia e Innovacion,Gobierno de Espana(Grant Nos.CGL2017-85045-P,PID2021-123189NB-I00,DI-17-09169)Government of Aragon(Grant No.Reference Group T20_23R)Jorge Sevil has a predoctoral contract(Grant No.PRE2018-084240)co-financed by the Spanish Government and the European Social Fund(ESF).
文摘The effectiveness of monitoring and early-warning systems for ground deformation phenomena,such as sinkholes,depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deformation preceding catastrophic failures.Sagging sinkholes with a slow subsidence rate and diffuse edges pose a significant challenge for subsidence monitoring due to the low deformation rates and limited lateral strain gradients.In this work,we satisfactorily illustrate the practicality of the Brillouin optical time domain analysis(BOTDA)to measure the spatial-temporal patterns of the vertical displacement in such challenging slow-moving sagging sinkholes.To assess the performance of the approach,we compare the strain recorded by the distributed optical fiber sensor with the vertical displacement measured by high-precision leveling.The results show a good spatial correlation with the ability to identify the maximum subsidence point.There is also a good temporal correlation with the detection of an acceleration phase in the subsidence associated with a flood event.
基金This work was supported by the National High Tech-nology Development 863 Program(2002aa404050)of China and the Foundation for Development of science of Shanghai(0114nm013),
文摘We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. Another Fabry-Perot interferometer is used to obtain the key initial angle of incidence.
基金Project supported by the National Natural Science Foundation of China (No. 51275465)the National Basic Research Program (973) of China (No. 2011CB013300)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China (No. [2011]1568)
文摘A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate.By accumulating the number of quarters in each direction and the specific position in the final quarter,the large-scale measurement is fulfilled.Displacements in Xand Y-direction can be measured independently and simultaneously.Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity.Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm.An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed.The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.
文摘In this paper, a sinusoidal phase-modulating Fabry-Perot interferometer is proposed to measure angular displacement. The usefulness of the interferometer is demonstrated by simulations and experiments.
基金The authors are grateful to the financial support by the Science and Technology Development Foundation, Education Commission of Beijing, P. R. China (No. 00KJ-094).
文摘This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system are described. The experimental results of thermal displacement of an electronic device are shown.
基金supported in part by the National Natural Science Foundation of China(No.62005194).
文摘In this Letter,we propose a simple structure of an orthogonal type double Michelson interferometer.The orthogonal detection method overcomes the problems of uneven ranging sensitivity and the inability of traditional interferometers to determine the displacement direction.The displacement measurement principle and signal processing method of the orthogonal double interferometer are studied.Unlike the arctangent algorithm,the displacement analysis uses the arc cosine algorithm,avoiding any pole limit in the distance analysis process.The minimum step size of the final experimental displacement system is 5 nm,which exhibits good repeatability,and the average error is less than 0.12 nm.
基金support from the US National Institute on Deafness and Other Communication Disorders(NIDCD R01 DC016079)is gratefully acknowledgedsupport by the Center for Holographic Studies and Laser micro-mechaTronics(CHSLT)at WPI.
文摘The auditory system of mammals enables the perception of sound from our surrounding world.Containing some of the smallest bones in the body,the ear transduces complex acoustic signals with high-temporal sensitivity to complex mechanical vibrations with magnitudes as small as tens of picometers.Measurements of the shape and acoustically induced motions of different components of the ear are essential if we are to expand our understanding of hearing mechanisms,and also provide quantitative information for the development of numerical ear models that can be used to improve hearing protection,clinical diagnosis,and repair of damaged or diseased ears.We are developing digital holographic methods and instrumentation using an ultra-high speed camera to measure shape and acoustically-induced motions in the middle ear.Specifically we study the eardrum,the first structure of the middle ear which initializes the acoustic-mechanical transduction of sound for hearing.Our measurement system is capable of performing holographic measurement at rates up to 2.1 M frames per second.Two shape measurement modalities had previously been implemented into our holographic systems:(1)a multi-wavelength method with a wavelength tunable laser;and(2)a multi-angle illumination method with a single wavelength laser.In this paper,we present a third method using a miniaturized fringe projection system with a microelectromechanical system(MEMS)mirror.Further,we optimize the processing of large data sets of holographic displacement measurements using a vectorized Pearson's correlation algorithm.We validate and compare the shape and displacement measurements of our methodologies using a National Institute of Standards and Technology(NIST)traceable gauge and sound-activated latex membranes and human eardrums.
基金supported financially by the National Natural Science Foundation of China (NSFC) (Grant No.51775378)the Key Projects in Tianjin Science&Technology Support Program (Grant No.19YFZC GX00890).
文摘Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.
基金supported by the National Natural Science Foundation of China under Grant No.51475262
文摘A signal processing method of realizing a large-range displacement measurement in a sinusoidal phase- modulating laser diode interferometer is proposed. The method of obtaining the dynamic value of the effective sinusoidal phase-modulating depth is detailed, and the residual amplitude modulation is also taken into account. Numerical simulations and experiments are carried out to compare this method with the traditional one. We prove that, with this method, the sinusoidal phase-modulating laser diode interferometer can realize a centimeter-level displacement measurement range with high precision, which is much better than the traditional method.
基金supported by the Office of Naval Research(Grant Nos.N00014-16-1-2094 and N00014-24-1-2547)the Lawrence Livermore National Laboratory(Grant No.B622827)the National Science Foundation.Y.-S.J.acknowledges support from KRISS(Grant Nos.25011026 and 25011211).
文摘Acoustic detection has many applications across science and technology from medicine to imaging and communications.However,most acoustic sensors have a common limitation in that the detection must be near the acoustic source.Alternatively,laser interferometry with picometer-scale motional displacement detection can rapidly and precisely measure sound-induced minute vibrations on remote surfaces.Here,we demonstrate the feasibility of sound detection up to 100 kHz at remote sites with≈60 m optical path length via laser homodyne interferometry.Based on our ultrastable hertz linewidth laser with 10-15 fractional stability,our laser interferometer achieves 0.5 pm/Hz1/2 displacement sensitivity near 10 kHz,bounded only by laser frequency noise over 10 kHz.Between 140 Hz and 15 kHz,we achieve a homodyne acoustic sensing sensitivity of subnanometer/Pascal across our conversational frequency overtones.The minimal sound pressure detectable over 60 m optical path length is≈2 mPa,with dynamic ranges over 100 dB.With the demonstrated standoff picometric distance metrology,we successfully detected and reconstructed musical scores of normal conversational volumes with high fidelity.The acoustic detection via this precision laser interferometer could be applied to selective area sound sensing for remote acoustic metrology,optomechanical vibrational motion sensing,and ultrasensitive optical microphones at the laser frequency noise limits.
基金supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant Nos. JP20K04171 and JP20H02038)。
文摘The sampling Moiré(SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. In this review, the basic principle of the SM method for measuring the twodimensional displacement and strain distributions is introduced. When the grid is not a standard orthogonal grating and cracks exist on the specimen surface, the measurement methods are also stated. Two of the most typical application examples are described in detail. One is the dynamic deflection measurement of a large-scale concrete bridge, and the other is the residual thermal strain measurement of small-scale flip chip packages. Several further development points of this method are pointed out. The SM method is expected to be used for deformation measurement of various structures and materials for residual stress evaluation, crack location prediction, and crack growth evaluation on broad scales.
基金This work was supported in part by the National Natural Science Foundation of China(U1808217)the National Science Fund for Distinguished Young Scholars(52125504)+1 种基金the Highlevel Personnel Innovation Support Program of Dalian(2017RJ04)the Liao Ning Revitalization Talents Program(XLYC1807086 and XLYC1801008).
文摘Three-dimensional(3D)microdisplacement monitoring plays a crucial role in the assembly of large aircraft.This paper presents a broadly applicable high-precision online 3D microdisplacement monitoring method and system based on proximity sensors as well as a corresponding in situ calibration method,which can be applied under various extreme working conditions encountered in the aircraft assembly process,such as compact and obstructed spaces.A 3D monitoring model is first established to achieve 3D microdisplacement monitoring based only on the one-dimensional distances measured by proximity sensors,which concerns the extrinsic sensor parameters,such as the probe base point(PBP)and the unit displacement vector(UDV).Then,a calibration method is employed to obtain these extrinsic parameters with high precision by combining spatial transformation principles and weighted optimization.Finally,calibration and monitoring experiments performed for a tailplane assembly process are reported.The calibration precision for the PBP is better than±10 lm in the X and Y directions and±2 lm in the Z direction,and the calibration precision for the UDV is better than 0.07°.Moreover,the accuracy of the 3D microdisplacement monitoring system can reach±15 lm.In general,this paper provides new insights into the modeling and calibration of 3D microdisplacement monitoring based on proximity sensors and a precise,efficient,and low-cost technical means for performing related measurements in compact spaces during the aircraft assembly process.
基金Supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(No.PolyU 5298/11E)the Hong Kong Polytechnic University(No.A-PD0H).
文摘Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dynamic displacement is then usually obtained indirectly from the double integration of the acceleration data.This paper reports an experimental method of measuring the displacement of stayed cables using a digital video camera.With the newly developed videogrammetric technique,the video clips are transferred into image frames,from which the shape and location of the target are identified.The displacement time history is then captured.The technique is applied to a cable-stayed bridge to measure the dynamic displacement of stay cables.The displacement is compared with the acceleration data in the frequency and time domains.The results show that the displacement measured by the digital video camera is comparable to the counterparts integrated from the acceleration data.The vibration frequencies identified from the acceleration are finally used to estimate the tension forces of the cables.The results show that the tension forces have insignificant changes after one year’s operation.
基金provided by the Program for New Century Excellent Talents in University (No. NCET-06-0477)the Independent Research Project of the State Key Laboratory of Coal Resources and Mine Safety of China University of Mining and Technology (No. SKLCRSM09X01)the Fundamental Research Funds for the Central Universities
文摘In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on.
文摘Based on laser-scanned measuring technology, a met ho d of on-line dynamic non-contact measurement and feedback control of processin g dimension, i.e. the double edges laser-scanned large diameter on-line dynami c measurement and control system is presented, which can be used to measure diam eter in large-scale machine part processing. In this paper, the working princip le, overall structure and microcomputer real-time control and data processing s ystem of the system are discussed in detail, the method of double edges scanned large diameter dimension measurement and control is theoretically analyzed, its possibility has been verified by experiments of lathing large diameters machine parts by a vertical lathe. The system adopts the measuring scheme of double edge s laser-scanned combined with grating displacement measurement. The two edges c haracteristic information of the measured diameter is given by the double edges laser-scanned measuring system, the non-contact measurement of large diameter dimension is realized to combine with the grating displacement measuring systems . The main controller gives out feedback control signal by means of measured res ults, and controls advance and retreat of lathe tool by the servo-control syste m of a vertical lathe to realize on-line dynamic non-contact measurement and c ontrol in processing.
文摘In this paper,a new direct optical triangulation(DOT) for measuring theout-of-plane displacement is given.In order to state its principle,DOT is used to measure a micro-displacement of a rigid body,and at the same time,the method of digital image processing is also given.
文摘This paper presents experiment results of the measurement conducted at the Roznew Dam power plant. For a course of starting and operating of turbo-plants, downstream face of the dam was monitored in relation to its eventual displacements on direction parallel to the construction axis. For the purpose of the experiment, geodetic measurement techniques and 2D DIC （digital image correlation） method （utilizing photographs of the object recorded with digital camera） were compared with regard to credibility, efficiency and accuracy. The vertical and horizontal displacements were monitored by tachometers measurements. The deformations in x-axis and y-axis on the wall surface was monitored by 2D DIC. It has been noticed that 2D DIC method is a surface method, continuous--not discreet. It allows for continuous observations of surface deformations, which is not possible in case of tachemetric measurements. Despite many advantages, the 2D DIC method lacks unambiguous evaluation of precision and relevance of designated displacements, which is rather significant for possibilities of utilization in technical control of large engineered objects. It should be also marked that the tachometric method is more reliable but is more laborious. Research of this type might comprise additional element for the assessment of the influence of dynamic loads, such as activating turbine water flow, onto the overall condition of the surveyed structure.
