This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measur...This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measurement system based on stereo deflectometry typically consists of a fringe-displaying screen,a main camera,and a reference camera.The arrangement of the components of a stereo deflectometry system is important for achieving high-accuracy measurements.In this paper,four geometric parameters of a stereo deflectometry system are analyzed and evaluated:the distance between the main camera and the measured object surface,the angle between the main camera ray and the surface normal,the distance between the fringe-displaying screen and the object,and the angle between the main camera and the reference camera.The influence of the geometric parameters on the measurement accuracy is evaluated.Experiments are performed using simulated and experimental data.The experimental results confirm the impact of these parameters on the measurement accuracy.A measurement system based on the proposed analysis has been set up to measure a stock concave mirror.Through a comparison of the given surface parameters of the concave mirror,a global measurement accuracy of 154.2 nm was achieved.展开更多
To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. E...To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. Experiments have been conducted over a range of nozzle pressure ratios from 3.0 to 6.0. Flow field issued from the new nozzle is quantitatively visualized by the rainbow schlieren deflectometry and compared with that from a conventional nozzle. Density fields in the free jets are reconstructed by the Abel inversion method for the schlieren images with the horizontal rainbow filter. The density values at the exit of the conventional nozzle obtained by the rainbow schlieren are compared with the analytical results by the flow model proposed in the past. In addition, Pitot probe surveys along the jet centerline were made to obtain the impact pressure distributions. The Mach number and velocity distributions along the jet centerline are obtained from a combination of the density and Pitot pressure data to clarify the fundamental flow structure of leek peeler nozzle jets.展开更多
The jet from a round Laval nozzle followed by a cylindrical duct with an inner diameter of 10 mm and a length of 50 mm is investigated experimentally. The Laval nozzle has a design Mach number of 1.5. Quantitative flo...The jet from a round Laval nozzle followed by a cylindrical duct with an inner diameter of 10 mm and a length of 50 mm is investigated experimentally. The Laval nozzle has a design Mach number of 1.5. Quantitative flow visualization of the jet issued from the duct exit is performed over a range of nozzle pressure ratios from 2.0 to 4.5 using the rainbow schlieren deflectometry combined with the computed tomography to investigate the jet three-dimensional structure. The flow features of the near-field shock systems in the jets are displayed with the density contour plot at the cross-section including the jet centerline. Effects of the nozzle pressure ratio on the density profile along the jet centerline are clarified quantitatively. In addition, a comparison between the present experiment and the previous one with a conventional Laval nozzle for jet centerline density profiles is carried out to examine the effect of the cylindrical duct. Furthermore, the three-dimensional structures of overexpanded and underexpanded jets are demonstrated with the isopycnic surfaces to visualize the internal flow features.展开更多
Deflectometry is a non-contact and rapid detection method with high sensitivity,which can be utilized in the areas of three-dimensional(3D)reconstruction,surface quality detection,and defect location.It has important ...Deflectometry is a non-contact and rapid detection method with high sensitivity,which can be utilized in the areas of three-dimensional(3D)reconstruction,surface quality detection,and defect location.It has important applications in the automotive industry,optical parts manufacturing,and other fields.Classical deflectometry methods require the integration of slope data to reconstruct the absolute surface shape.However,the integration procedure is error-prone due to the accumulation of random errors into large shape deviations,resulting in inaccurate measurement results.In this paper,we extract the position of the centerline of the bright fringe from the stripe image and find the center of the fringe line point by point.Using the principle of triangulation,the 3D data for the object’s shaped surface can be obtained.In addition,infrared light enhances specular reflection,resulting in better deflectometry performance than that of visible light.Experiments show that the proposed method is sensitive to the changes in height and can roughly restore the surface topography of the object without calibration.展开更多
This paper presents a short review for phase measuring deflectometry (PMD). PMD isa phase calculation based technique for three-dimensional (3D) measurement ofspecular surfaces. PMD can achieve nano-scale form measure...This paper presents a short review for phase measuring deflectometry (PMD). PMD isa phase calculation based technique for three-dimensional (3D) measurement ofspecular surfaces. PMD can achieve nano-scale form measurement accuracy with theadvantages of high dynamic range, non-contact, full field measurement which makesit a competitive method for specular surface measurement. With the development ofcomputer science, display and imaging technology, there has been an advancementin speed for PMD in recent years. This paper discusses PMD focusing on the difference onits system configuration. Measurement principles, progress, advantages and problems arediscussed for each category. The challenges and future development of PMD are alsodiscussed.展开更多
Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a...Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a promising tool,since it permits simultaneous single-shot X-ray radiography and phase-contrast imaging of dense plasmas.We present the results of an experiment at OMEGA EP that aims to probe the ablation front of a laser-irradiated foil using a Talbot–Lau X-ray interferometer.A polystyrene(CH)foil was irradiated by a laser of 133 J,1 ns and probed with 8 keV laser-produced backlighter radiation from Cu foils driven by a short-pulse laser(153 J,11 ps).The ablation front interferograms were processed in combination with a set of reference images obtained ex situ using phase-stepping.We managed to obtain attenuation and phase-shift images of a laser-irradiated foil for electron densities above 1022 cm−3.These results showcase the capabilities of Talbot–Lau X-ray diagnostic methods to diagnose HED laser-generated plasmas through high-resolution imaging.展开更多
Usually,a multilens optical system is composed of multiple undetectable sublenses.Wavefront of a multilens optical system cannot be measured when classical transmitted phase measuring deflectometry[PMD] is used.In thi...Usually,a multilens optical system is composed of multiple undetectable sublenses.Wavefront of a multilens optical system cannot be measured when classical transmitted phase measuring deflectometry[PMD] is used.In this study,a wavefront measuring method for an optical system with multiple optics is presented based on PMD.A paraxial plane is used to represent the test multilens optical system.We introduce the calibration strategy and mathematical deduction of gradient equations.Systematic errors are suppressed with an N-rotation test.Simulations have been performed to demonstrate our method.The results showing the use of our method in multilens optical systems,such as the collimator and single-lens reflex camera lenses show that the measurement accuracy is comparable with those of interferometric tests.展开更多
A developing application of laser-driven currents is the generation of magnetic fields of picosecond-nanosecond duration with magnitudes exceeding B=10 T.Single-loop and helical coil targets can direct laser-driven di...A developing application of laser-driven currents is the generation of magnetic fields of picosecond-nanosecond duration with magnitudes exceeding B=10 T.Single-loop and helical coil targets can direct laser-driven discharge currents along wires to generate spatially uniform,quasi-static magnetic fields on the millimetre scale.Here,we present proton deflectometry across two axes of a single-loop coil ranging from 1 to 2 mm in diameter.Comparison with proton tracking simulations shows that measured magnetic fields are the result of kiloampere currents in the coil and electric charges distributed around the coil target.Using this dual-axis platform for proton deflectometry,robust measurements can be made of the evolution of magnetic fields in a capacitor coil target.展开更多
Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Fo...Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Form accuracy of the structured surfaces directly impacts the functioning of the specular components.Because the scales of these structures and/or the importance of their functions are usually designed differently,the structures require different measurement demands in scale,lateral resolution,and accuracy.In this paper,a multiscale form measurement technique is proposed based on triple-sensor phase measuring deflectometry for measuring structured specular surfaces.The proposed technique contains two sub-phase measuring deflectometry(PMD)-systems.Each sub-system works as a single segmentation PMD(SPMD)system and is designed to have different measurement scales,lateral resolutions,and accuracies to meet the measurement demands of the targeted surfaces.Two imaging sensors in the proposed technique cover the measured full-scale surface.The specular surface is separated into several continuous segments through algorithms and the spatial relationship of the continuous segments is established based on absolute depth data calculated through the triangular relationship between the two imaging sensors.The third imaging sensor with a long working distance only captures thefield of the small-scale structures and reconstructs the structures based on gradient data to improve the structures’reconstruction resolution and accuracy.In order to make it suitable for portable and embedded measurement,a compact configuration is explored to reduce system volume.Data fusion techniques are also studied to combine the measurement data of the two sub-systems.Experimental results demonstrate the validity of a portable prototype developed based on the proposed technique by measuring a concave mirror with small-scale structures.展开更多
Two-dimensional critical nozzle flows at low Reynolds numbers are visualized by the rainbow schlieren deflectometry. Experiments have been performed in a region of overexpanded nozzle flow. The variation of the shock ...Two-dimensional critical nozzle flows at low Reynolds numbers are visualized by the rainbow schlieren deflectometry. Experiments have been performed in a region of overexpanded nozzle flow. The variation of the shock structure against the back pressure ratio can be clearly visible with color gradation. Static pressure rises due to the shock-induced flow separation are compared with the previous theories. The unsteady characteristics of overexpanded critical nozzle flows at low Reynolds numbers are quantitatively and qualitatively visualized using laser schlieren and Mach-Zehnder interferometer systems combined with a high-speed digital camera. It was found that an oscillating normal shock wave appears inside the nozzle, and that the shock wave has a specified dominant frequency. Also the time-history of the oscillating shock wave is obtained from both the systems and compared with each other.展开更多
Monolithic multi-freeform optical structures play significant roles in advanced optical systems by simplifying system structures and enhancing optoelectronic performance.However,manufacturing and measurement present s...Monolithic multi-freeform optical structures play significant roles in advanced optical systems by simplifying system structures and enhancing optoelectronic performance.However,manufacturing and measurement present significant challenges,which require the simultaneous assurance of form quality and relative positioning of multiple functional surfaces.Consequently,a deterministic form-position deflectometric measuring method is proposed based on Bayesian multisensor fusion,which effectively overcomes the inherent limitation of deflectometry in absolute positioning.Calibration priors were marginalised in the measurement model to improve fidelity,and a fully probabilistic measurement framework was proposed to eliminate numerical bias in conventional sequential optimisation approaches.Finally,a geometric-constraint-based registration method was developed to evaluate the form-position quality of freeform surfaces.The experimental results demonstrated the measurement accuracy could achieve a level of one hundred nanometres for surface forms and a few microns for surface positions.展开更多
Full-field three-dimensional(3D)measurement technology based on phase information has become an indispensable part of geometric dimension measurement in modern scientific research and engineering applications.This fie...Full-field three-dimensional(3D)measurement technology based on phase information has become an indispensable part of geometric dimension measurement in modern scientific research and engineering applications.This field has been developing and evolving for the study of highly reflective phenomena,diffuse reflections,and specular surfaces,and many novel methods have emerged to increase the speed of measurements,enhance data accuracy,and broaden the robustness of the system.Herein,we will discuss the latest research progress in full-field 3D shape measurement based on phase information systematically and comprehensively.First,the fundamentals of 3D shape measurement based on phase information are introduced,namely,phase-shifting and transform-based methods.Second,recent technological innovations are highlighted,including increases in measurement speed and automation and improvements in robustness in complex environments.In particular,the challenges faced by these technological advances in solving highly dynamic,composite surface measurement problems are presented,i.e.,with multiexposure techniques proposed for high dynamics that extend the dynamic range of the camera to reduce the effects of overexposure but increase the cost of time and have high hardware requirements,fringe adaptive techniques that overcome light variations but are computationally complex,and multipolarized camera techniques that reduce the effects of light variations but are sensitive to the light source.Third,the phase-shifting method combined with coding is proposed to improve the measurement speed,but the accuracy is slightly reduced.Deep learning techniques are proposed to cope with measurements in complex environments,but the dataset computation process is cumbersome.Finally,future research directions are suggested,and the challenges are presented.Overall,this work provides a reference for researchers and engineers.展开更多
文摘This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measurement system based on stereo deflectometry typically consists of a fringe-displaying screen,a main camera,and a reference camera.The arrangement of the components of a stereo deflectometry system is important for achieving high-accuracy measurements.In this paper,four geometric parameters of a stereo deflectometry system are analyzed and evaluated:the distance between the main camera and the measured object surface,the angle between the main camera ray and the surface normal,the distance between the fringe-displaying screen and the object,and the angle between the main camera and the reference camera.The influence of the geometric parameters on the measurement accuracy is evaluated.Experiments are performed using simulated and experimental data.The experimental results confirm the impact of these parameters on the measurement accuracy.A measurement system based on the proposed analysis has been set up to measure a stock concave mirror.Through a comparison of the given surface parameters of the concave mirror,a global measurement accuracy of 154.2 nm was achieved.
文摘To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. Experiments have been conducted over a range of nozzle pressure ratios from 3.0 to 6.0. Flow field issued from the new nozzle is quantitatively visualized by the rainbow schlieren deflectometry and compared with that from a conventional nozzle. Density fields in the free jets are reconstructed by the Abel inversion method for the schlieren images with the horizontal rainbow filter. The density values at the exit of the conventional nozzle obtained by the rainbow schlieren are compared with the analytical results by the flow model proposed in the past. In addition, Pitot probe surveys along the jet centerline were made to obtain the impact pressure distributions. The Mach number and velocity distributions along the jet centerline are obtained from a combination of the density and Pitot pressure data to clarify the fundamental flow structure of leek peeler nozzle jets.
文摘The jet from a round Laval nozzle followed by a cylindrical duct with an inner diameter of 10 mm and a length of 50 mm is investigated experimentally. The Laval nozzle has a design Mach number of 1.5. Quantitative flow visualization of the jet issued from the duct exit is performed over a range of nozzle pressure ratios from 2.0 to 4.5 using the rainbow schlieren deflectometry combined with the computed tomography to investigate the jet three-dimensional structure. The flow features of the near-field shock systems in the jets are displayed with the density contour plot at the cross-section including the jet centerline. Effects of the nozzle pressure ratio on the density profile along the jet centerline are clarified quantitatively. In addition, a comparison between the present experiment and the previous one with a conventional Laval nozzle for jet centerline density profiles is carried out to examine the effect of the cylindrical duct. Furthermore, the three-dimensional structures of overexpanded and underexpanded jets are demonstrated with the isopycnic surfaces to visualize the internal flow features.
基金supported by the Talent Project of Chengdu Technological University,China(Grant No.2023RC013).
文摘Deflectometry is a non-contact and rapid detection method with high sensitivity,which can be utilized in the areas of three-dimensional(3D)reconstruction,surface quality detection,and defect location.It has important applications in the automotive industry,optical parts manufacturing,and other fields.Classical deflectometry methods require the integration of slope data to reconstruct the absolute surface shape.However,the integration procedure is error-prone due to the accumulation of random errors into large shape deviations,resulting in inaccurate measurement results.In this paper,we extract the position of the centerline of the bright fringe from the stripe image and find the center of the fringe line point by point.Using the principle of triangulation,the 3D data for the object’s shaped surface can be obtained.In addition,infrared light enhances specular reflection,resulting in better deflectometry performance than that of visible light.Experiments show that the proposed method is sensitive to the changes in height and can roughly restore the surface topography of the object without calibration.
基金funded by the Engineering and Physical Sciences Research Council(EPSRC)of the UK with the funding of the EPSRC Centre for Innovative Manufacturing in Advanced Metrology(Grand Ref:EP/I033424/1)the EPSRC Future Advanced Metrology Hub(EP/P006930/1).
文摘This paper presents a short review for phase measuring deflectometry (PMD). PMD isa phase calculation based technique for three-dimensional (3D) measurement ofspecular surfaces. PMD can achieve nano-scale form measurement accuracy with theadvantages of high dynamic range, non-contact, full field measurement which makesit a competitive method for specular surface measurement. With the development ofcomputer science, display and imaging technology, there has been an advancementin speed for PMD in recent years. This paper discusses PMD focusing on the difference onits system configuration. Measurement principles, progress, advantages and problems arediscussed for each category. The challenges and future development of PMD are alsodiscussed.
基金supported by the National Nuclear Security Administration (DENA0003882)funding from the Conseil Règional Aquitaine (INTALAX)+1 种基金the Agence Nationale de la Recherche (ANR-10-IDEX-03-02, ANR-15CE30-0011)supported by Research Grant No. PID2019-108764RB-I00 from the Spanish Ministry of Science and Innovation
文摘Diagnosing the evolution of laser-generated high energy density(HED)systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions.Talbot–Lau interferometry constitutes a promising tool,since it permits simultaneous single-shot X-ray radiography and phase-contrast imaging of dense plasmas.We present the results of an experiment at OMEGA EP that aims to probe the ablation front of a laser-irradiated foil using a Talbot–Lau X-ray interferometer.A polystyrene(CH)foil was irradiated by a laser of 133 J,1 ns and probed with 8 keV laser-produced backlighter radiation from Cu foils driven by a short-pulse laser(153 J,11 ps).The ablation front interferograms were processed in combination with a set of reference images obtained ex situ using phase-stepping.We managed to obtain attenuation and phase-shift images of a laser-irradiated foil for electron densities above 1022 cm−3.These results showcase the capabilities of Talbot–Lau X-ray diagnostic methods to diagnose HED laser-generated plasmas through high-resolution imaging.
基金supported by the City Foundation of Nanchong(Nos.SXQHJH026 and 2021SXHZ041)。
文摘Usually,a multilens optical system is composed of multiple undetectable sublenses.Wavefront of a multilens optical system cannot be measured when classical transmitted phase measuring deflectometry[PMD] is used.In this study,a wavefront measuring method for an optical system with multiple optics is presented based on PMD.A paraxial plane is used to represent the test multilens optical system.We introduce the calibration strategy and mathematical deduction of gradient equations.Systematic errors are suppressed with an N-rotation test.Simulations have been performed to demonstrate our method.The results showing the use of our method in multilens optical systems,such as the collimator and single-lens reflex camera lenses show that the measurement accuracy is comparable with those of interferometric tests.
基金This paper was supported by the LLNL Academic Partnership in ICF,EPSRC grants EP/L01663X/1 and EP/L000644/1the Czech Republic MSMT targeted support of Large Infrastructures+1 种基金ELI Beamlines Project LQ1606 of the National Programme of Sustainability IIThe contribution of the JIHT RAS team was completed within the framework of the Russian Ministry state assignment for Science and Higher Education(topic#01201357846).
文摘A developing application of laser-driven currents is the generation of magnetic fields of picosecond-nanosecond duration with magnitudes exceeding B=10 T.Single-loop and helical coil targets can direct laser-driven discharge currents along wires to generate spatially uniform,quasi-static magnetic fields on the millimetre scale.Here,we present proton deflectometry across two axes of a single-loop coil ranging from 1 to 2 mm in diameter.Comparison with proton tracking simulations shows that measured magnetic fields are the result of kiloampere currents in the coil and electric charges distributed around the coil target.Using this dual-axis platform for proton deflectometry,robust measurements can be made of the evolution of magnetic fields in a capacitor coil target.
基金supported by the UK’s Engineering and Physical Sciences Research Council(EPSRC)funding of“The EPSRC Future Advanced Metrology Hub”(EP/P006930/1)the funding of“A Multiscale Digital Twin-Driven Smart Manufacturing System for High Value-Added Products”(EP/T024844/1).
文摘Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Form accuracy of the structured surfaces directly impacts the functioning of the specular components.Because the scales of these structures and/or the importance of their functions are usually designed differently,the structures require different measurement demands in scale,lateral resolution,and accuracy.In this paper,a multiscale form measurement technique is proposed based on triple-sensor phase measuring deflectometry for measuring structured specular surfaces.The proposed technique contains two sub-phase measuring deflectometry(PMD)-systems.Each sub-system works as a single segmentation PMD(SPMD)system and is designed to have different measurement scales,lateral resolutions,and accuracies to meet the measurement demands of the targeted surfaces.Two imaging sensors in the proposed technique cover the measured full-scale surface.The specular surface is separated into several continuous segments through algorithms and the spatial relationship of the continuous segments is established based on absolute depth data calculated through the triangular relationship between the two imaging sensors.The third imaging sensor with a long working distance only captures thefield of the small-scale structures and reconstructs the structures based on gradient data to improve the structures’reconstruction resolution and accuracy.In order to make it suitable for portable and embedded measurement,a compact configuration is explored to reduce system volume.Data fusion techniques are also studied to combine the measurement data of the two sub-systems.Experimental results demonstrate the validity of a portable prototype developed based on the proposed technique by measuring a concave mirror with small-scale structures.
文摘Two-dimensional critical nozzle flows at low Reynolds numbers are visualized by the rainbow schlieren deflectometry. Experiments have been performed in a region of overexpanded nozzle flow. The variation of the shock structure against the back pressure ratio can be clearly visible with color gradation. Static pressure rises due to the shock-induced flow separation are compared with the previous theories. The unsteady characteristics of overexpanded critical nozzle flows at low Reynolds numbers are quantitatively and qualitatively visualized using laser schlieren and Mach-Zehnder interferometer systems combined with a high-speed digital camera. It was found that an oscillating normal shock wave appears inside the nozzle, and that the shock wave has a specified dominant frequency. Also the time-history of the oscillating shock wave is obtained from both the systems and compared with each other.
基金supported by the National Natural Science Foundation of China(52475551)the Natural Science Foundation of Shanghai(24ZR1406800)the Dreams Foundation of Jianghuai Advanced Technology Center(2023-ZM01C008).
文摘Monolithic multi-freeform optical structures play significant roles in advanced optical systems by simplifying system structures and enhancing optoelectronic performance.However,manufacturing and measurement present significant challenges,which require the simultaneous assurance of form quality and relative positioning of multiple functional surfaces.Consequently,a deterministic form-position deflectometric measuring method is proposed based on Bayesian multisensor fusion,which effectively overcomes the inherent limitation of deflectometry in absolute positioning.Calibration priors were marginalised in the measurement model to improve fidelity,and a fully probabilistic measurement framework was proposed to eliminate numerical bias in conventional sequential optimisation approaches.Finally,a geometric-constraint-based registration method was developed to evaluate the form-position quality of freeform surfaces.The experimental results demonstrated the measurement accuracy could achieve a level of one hundred nanometres for surface forms and a few microns for surface positions.
基金Foundation of China(U2341275,52075147)Scientific research project of Education Department of Hebei Province(JZX2024021).
文摘Full-field three-dimensional(3D)measurement technology based on phase information has become an indispensable part of geometric dimension measurement in modern scientific research and engineering applications.This field has been developing and evolving for the study of highly reflective phenomena,diffuse reflections,and specular surfaces,and many novel methods have emerged to increase the speed of measurements,enhance data accuracy,and broaden the robustness of the system.Herein,we will discuss the latest research progress in full-field 3D shape measurement based on phase information systematically and comprehensively.First,the fundamentals of 3D shape measurement based on phase information are introduced,namely,phase-shifting and transform-based methods.Second,recent technological innovations are highlighted,including increases in measurement speed and automation and improvements in robustness in complex environments.In particular,the challenges faced by these technological advances in solving highly dynamic,composite surface measurement problems are presented,i.e.,with multiexposure techniques proposed for high dynamics that extend the dynamic range of the camera to reduce the effects of overexposure but increase the cost of time and have high hardware requirements,fringe adaptive techniques that overcome light variations but are computationally complex,and multipolarized camera techniques that reduce the effects of light variations but are sensitive to the light source.Third,the phase-shifting method combined with coding is proposed to improve the measurement speed,but the accuracy is slightly reduced.Deep learning techniques are proposed to cope with measurements in complex environments,but the dataset computation process is cumbersome.Finally,future research directions are suggested,and the challenges are presented.Overall,this work provides a reference for researchers and engineers.
