A real-time arc welding robot visual control system based on a local network with a multi-level hierarchy is developed in this paper. It consists of an intelligence and human-machine interface level, a motion planning...A real-time arc welding robot visual control system based on a local network with a multi-level hierarchy is developed in this paper. It consists of an intelligence and human-machine interface level, a motion planning level, a motion control level and a servo control level. The last three levels form a local real-time open robot controller, which realizes motion planning and motion control of a robot. A camera calibration method based on the relative movement of the end-effector connected to a robot is proposed and a method for tracking weld seam based on the structured light stereovision is provided. Combining the parameters of the cameras and laser plane, three groups of position values in Cartesian space are obtained for each feature point in a stripe projected on the weld seam. The accurate three-dimensional position of the edge points in the weld seam can be calculated from the obtained parameters with an information fusion algorithm. By calculating the weld seam parameter from position and image data, the movement parameters of the robot used for tracking can be determined. A swing welding experiment of type V groove weld is successfully conducted, the results of which show that the system has high resolution seam tracking in real-time, and works stably and efficiently.展开更多
The interest in tailoring light in all its degrees of freedom is steadily gaining traction,driven by the tremendous developments in the toolkit for the creation,control and detection of what is now called structured l...The interest in tailoring light in all its degrees of freedom is steadily gaining traction,driven by the tremendous developments in the toolkit for the creation,control and detection of what is now called structured light.Because the complexity of these optical fields is generally understood in terms of interference,the tools have historically been linear optical elements that create the desired superpositions.For this reason,despite the long and impressive history of nonlinear optics,only recently has the spatial structure of light in nonlinear processes come to the fore.In this review we provide a concise theoretical framework for understanding nonlinear optics in the context of structured light,offering an overview and perspective on the progress made,and the challenges that remain.展开更多
Digital structured light (SL) profilometry is increasingly used in three-dimensional (3D) measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measure...Digital structured light (SL) profilometry is increasingly used in three-dimensional (3D) measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.展开更多
In order to realize the closed-loop control for rapid prototyping process based on gas metal arc welding, the geometric parameters of weld beads should be detected. In this study, a vision sensor system consisting of ...In order to realize the closed-loop control for rapid prototyping process based on gas metal arc welding, the geometric parameters of weld beads should be detected. In this study, a vision sensor system consisting of a linear laser projector and a CCD camera was designed to collect images of weld beads. Then, an image processing approach which combines with a Gaassian filter and an improved gravity method was used to extract the centerline of a light stripe based on VC ++. Feature points of the centerline were identical directly by means of an image fusion algorithm. Experimental results show that image fusion is an effective approach to measure the width and height of the weld bead with high accuracy. This method can identify beads effectively in multi-pass welding and avoid designing different modes to suit all kinds of shapes.展开更多
Three-dimensional(3D)reconstruction using structured light projection has the characteristics of non-contact,high precision,easy operation,and strong real-time performance.However,for actual measurement,projection mod...Three-dimensional(3D)reconstruction using structured light projection has the characteristics of non-contact,high precision,easy operation,and strong real-time performance.However,for actual measurement,projection modulated images are disturbed by electronic noise or other interference,which reduces the precision of the measurement system.To solve this problem,a 3D measurement algorithm of structured light based on deep learning is proposed.The end-to-end multi-convolution neural network model is designed to separately extract the coarse-and fine-layer features of a 3D image.The point-cloud model is obtained by nonlinear regression.The weighting coefficient loss function is introduced to the multi-convolution neural network,and the point-cloud data are continuously optimized to obtain the 3D reconstruction model.To verify the effectiveness of the method,image datasets of different 3D gypsum models were collected,trained,and tested using the above method.Experimental results show that the algorithm effectively eliminates external light environmental interference,avoids the influence of object shape,and achieves higher stability and precision.The proposed method is proved to be effective for regular objects.展开更多
A 3D surface reconstruction method using a binocular stereo vision technology and a coded structured light,which combines a gray code with phase-shift has been studied.The accuracy of the 3 D surface reconstruction ma...A 3D surface reconstruction method using a binocular stereo vision technology and a coded structured light,which combines a gray code with phase-shift has been studied.The accuracy of the 3 D surface reconstruction mainly depends on the decoding of gray code views and phase-shift views.In order to find the boundary accurately,gray code patterns and their inverses are projected onto a human eye plaster model.The period dislocation between the gray code views and the phase-shift views in the course of decoding has been analyzed and a new method has been proposed to solve it.The splicing method is based on feature points.The result of the 3D surface reconstruction shows the accuracy and reliability of our method.展开更多
M-arrays are random arrays in which an appropriate sub-window appears only once in the whole array. Coded structured light based on M-arrays is one=shot technique to rapidly acquire 3D information of unknown surfaces ...M-arrays are random arrays in which an appropriate sub-window appears only once in the whole array. Coded structured light based on M-arrays is one=shot technique to rapidly acquire 3D information of unknown surfaces by projecting suitable patterns onto a measuring surface. This paper presents a method to construct large size M-arrays based on the piece growing algorithm in which an array is constructed by many pieces through splicing each other. Reconstructing 3D shapes by utilizing the designed pattern based on constructed M-arrays for two objects are given.展开更多
Aiming at the problem that the existence of disturbances on the edges of light-stripe makes the segmentation of the light-stripes images difficult, a new segmentation algorithm based on edge-searching is presented. It...Aiming at the problem that the existence of disturbances on the edges of light-stripe makes the segmentation of the light-stripes images difficult, a new segmentation algorithm based on edge-searching is presented. It firstly calculates every edge pixel's horizontal coordinate grads to produce the corresponding grads-edge, then uses a designed length-variable l D template to scan the light-stripes' grads-edges. The template is able to find the disturbances with different width utilizing the distributing character of the edge disturbances. The found disturbances are eliminated finally. The algorithm not only can smoothly segment the light-stripes images, but also eliminate most disturbances on the light-stripes' edges without damaging the light-stripes images' 3D information. A practical example of using the proposed algorithm is given in the end. It is proved that the efficiency of the algorithm has been improved obviously by comparison.展开更多
A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway...A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway groove by a DLP projector, and distorting of stripes is happened on the raceway. Simultaneously, aided by three-step phase-shifting approach, three images covered by different stripes are obtained by a high-resolution CCD camera at the same location, thus a more accuracy local topography can be obtained. And then the bearing is rotated on a high precision computer controlled rotational stage. Three images are also obtained as the former step at next planned location triggered by the motor. After one cycle, all images information is combined through the mosaics. As a result, the 3D information of raceway groove can be gained. Not only geometric properties but also surface flaws can be extracted by software. A preliminary hardware system has been built, with which some geometric parameters have been extracted from reconstructed local topography.展开更多
Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is app...Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is applied to measure the out-of-plane deformation of structures with one-shot projection.Through color fringe recognizing,decoding and triangulation processing for the captured images corresponding to each deformation state,the feasibility of the method is testified by the measurement of elastic deflections of a flexible square plate,showing good agreement with those from the calibrated displacement driver.The plastic deformation of two alloy aluminum rectangular tubes is measured to show the technique application to surface topographic evaluation of the buckling structures with large displacements.展开更多
Since unmanned ground vehicles often encounter concave and convex obstacles in wild ground, a filtering algorithm using line structured light to detect these long distance obstacles is proposed. For the line structure...Since unmanned ground vehicles often encounter concave and convex obstacles in wild ground, a filtering algorithm using line structured light to detect these long distance obstacles is proposed. For the line structured light image, a ranked-order based adaptively extremum median (RAEM) filter algorithm on salt and pepper noise is presented. In the algorithm, firstly effective points and noise points in a filtering window are differentiated; then the gray values of noise points are replaced by the medium of gray values of the effective pixels, with the efficient points' gray values unchanged; in the end this algorithm is proved to be efficient by experiments. Experimental resuits demonstrate that the image blur, resulting into proposed algorithm can remove noise points effectively and minimize the protecting the edge information as much as possible.展开更多
Spatial light modulators,as dynamic flat-panel optical devices,have witnessed rapid development over the past two decades,concomitant with the advancements in micro-and opto-electronic integration technology.In partic...Spatial light modulators,as dynamic flat-panel optical devices,have witnessed rapid development over the past two decades,concomitant with the advancements in micro-and opto-electronic integration technology.In particular,liquid-crystal spatial light modulator(LC-SLM)technologies have been regarded as versatile tools for generating arbitrary optical fields and tailoring all degrees of freedom beyond just phase and amplitude.These devices have gained significant interest in the nascent field of structured light in space and time,facilitated by their ease of use and real-time light manipulation,fueling both fundamental research and practical applications.Here we provide an overview of the key working principles of LC-SLMs and review the significant progress made to date in their deployment for various applications,covering topics as diverse as beam shaping and steering,holography,optical trapping and tweezers,measurement,wavefront coding,optical vortex,and quantum optics.Finally,we conclude with an outlook on the potential opportunities and technical challenges in this rapidly developing field.展开更多
Behavior of structure light is investigated by monitoring probe absorption using a microwave-driven Y-type atomic media configuration.The system under consideration is driven by one of the control vortex beams as well...Behavior of structure light is investigated by monitoring probe absorption using a microwave-driven Y-type atomic media configuration.The system under consideration is driven by one of the control vortex beams as well as an extra non-vortex control beam to ensure electromagnetically induced transparency.The significant aspect in the generation of structured light is the azimuthal phase-dependent modification for probe absorption.Further intensity distribution for absorption spectra is examined for simultaneously evaluating both the control vortex beams.We also go through the radial distribution of intensity for various orbital angular momentum values.Different modes of structural beams may be distinguished using the suggested approach.Our research gives us a way for rapidly transferring vortex wavefronts from control field to probe absorption profile.This could be useful in quantum information processing.展开更多
Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more devel...Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more development opportunities.As an indispensable part of light wood structure systems,the wood-frame shear wall plays a vital role in the bearing capacity and earthquake resistance of light wood structure systems.This paper is focused on a review of the lateral performance of wood-frame shear walls and classifies the influencing factors in relevant experimental research into three categories,including internal factors such as shear wall structure,external factors such as test scheme,and other factors of material production and test process.Finally,the research prospects in this field were introduced based on the summary of the research status.This work can be a reference for further research on the lateral performance of wood-frame shear walls.展开更多
In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structur...In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction;thus they provide technical and cost advantages. The insitu laser machining system realizes a simple operation process by integrating measurement and machining,which greatly reduces labor and time costs.展开更多
3D reconstruction of worn parts is the foundation for remanufacturing system based on robotic arc welding, because it can provide 3D geometric information for robot task plan. In this investigation, a novel 3D reconst...3D reconstruction of worn parts is the foundation for remanufacturing system based on robotic arc welding, because it can provide 3D geometric information for robot task plan. In this investigation, a novel 3D reconstruction system based on linear structured light vision sensing is developed. This system hardware consists of a MTC368-CB CCD camera, a MLH-645 laser projector and a DH-CG300 image grabbing card. This system software is developed to control the image data capture. In order to reconstruct the 3D geometric information from the captured image, a two steps rapid calibration algorithm is proposed. The 3D reconstruction experiment shows a satisfactory result.展开更多
In the present study,the formula calculating ship impact forces on light wharf structures is presented when the elastic deformation of the hull and the pier structures as well as the nonlinear deformation of the fende...In the present study,the formula calculating ship impact forces on light wharf structures is presented when the elastic deformation of the hull and the pier structures as well as the nonlinear deformation of the fender are taken into account. The ship impact forces are statistically analyzed with the Monte-Carlo method according to the known probability distribution types of random variables.Based on the simulated results, the distribution of ship impact forces which is characterized by bimodal distribution can be expressed as the combining probability density function of beta distribution and normal distribution. The corresponding parameters of the probability density function can be estimated with the maximum likelihood method. The results show that ship impact forces on light wharf structures follow the distribution of type I extreme value.The mean coefficient and variation coefficient are 1.11 and 0.008 respectively during 50 years of design reference period.展开更多
Structured light is routinely used in free-space optical communication channels,both classical and quantum,where information is encoded in the spatial structure of the mode for increased bandwidth.Both real-world and ...Structured light is routinely used in free-space optical communication channels,both classical and quantum,where information is encoded in the spatial structure of the mode for increased bandwidth.Both real-world and experimentally simulated turbulence conditions have revealed that free-space structured light modes are perturbed in some manner by turbulence,resulting in both amplitude and phase distortions,and consequently,much attention has focused on whether one mode type is more robust than another,but with seemingly inconclusive and contradictory results.We present complex forms of structured light that are invariant under propagation through the atmosphere:the true eigenmodes of atmospheric turbulence.We provide a theoretical procedure for obtaining these eigenmodes and confirm their invariance both numerically and experimentally.Although we have demonstrated the approach on atmospheric turbulence,its generality allows it to be extended to other channels too,such as aberrated paths,underwater,and in optical fiber.展开更多
The creation of three-dimensional models from an unorganized set of points is an active research area in computer graphics.One of the purposes of this study is to explore the 3D reconstruction of a cube-type artificia...The creation of three-dimensional models from an unorganized set of points is an active research area in computer graphics.One of the purposes of this study is to explore the 3D reconstruction of a cube-type artificial reef(CTAR)set by linear structured light and binocular stereo vision technology in an underwater environment.The experimental setup is composed of two ca-meras in a stereo vision configuration.The alpha shapes method can be used to construct a surface that most closely reflects the arti-ficial reef set described by the points.A parameter study is conducted to assess the scales of the set(i.e.,usable volume,surface area,projected area,height,and base diameter)on the basis of 3D reconstruction.Experimental results show that the quality of 3D recon-struction in an underwater environment is acceptable for estimating the scale size of the CTAR set.According to the measurement of the scale sizing of the CTAR set,the relationships between the parameters of the CTAR set and the number of CTAR modules were determined.Moreover,the usable volume of the CTAR set can be estimated depending on the basis of the number of CTAR modules.展开更多
The binocular stereo vision system is often used to reconstruct 3D point clouds of an object.However,it is challenging to find effective matching points in two object images with similar color or less texture.This wil...The binocular stereo vision system is often used to reconstruct 3D point clouds of an object.However,it is challenging to find effective matching points in two object images with similar color or less texture.This will lead to mismatching by using the stereo matching algorithm to calculate the disparity map.In this context,the object can’t be reconstructed precisely.As a countermeasure,this study proposes to combine the Gray code fringe projection with the binocular camera as well as to generate denser point clouds by projecting an active light source to increase the texture of the object,which greatly reduces the reconstruction error caused by the lack of texture.Due to the limitation of the camera viewing angle,a one-perspective binocular camera can only reconstruct the 2.5D model of an object.To obtain the 3D model of an object,point clouds obtained from multiple-view images are processed by coarse registration using the coarse SAC-IA algorithm and fine registration using the ICP algorithm,which is followed by voxel filtering fusion of the point cloud.To improve the reconstruction quality,a polarizer is mounted in front of the cameras to filter out the redundant reflected light.Eventually,the 3D model and the dimension of a vase are obtained after calibration.展开更多
基金This work was supported by the National High Technology Research and Development Program of China under Grant 2002AA422160 by the National Key Fundamental Research and the Devel-opment Project of China (973) under Grant 2002CB312200.
文摘A real-time arc welding robot visual control system based on a local network with a multi-level hierarchy is developed in this paper. It consists of an intelligence and human-machine interface level, a motion planning level, a motion control level and a servo control level. The last three levels form a local real-time open robot controller, which realizes motion planning and motion control of a robot. A camera calibration method based on the relative movement of the end-effector connected to a robot is proposed and a method for tracking weld seam based on the structured light stereovision is provided. Combining the parameters of the cameras and laser plane, three groups of position values in Cartesian space are obtained for each feature point in a stripe projected on the weld seam. The accurate three-dimensional position of the edge points in the weld seam can be calculated from the obtained parameters with an information fusion algorithm. By calculating the weld seam parameter from position and image data, the movement parameters of the robot used for tracking can be determined. A swing welding experiment of type V groove weld is successfully conducted, the results of which show that the system has high resolution seam tracking in real-time, and works stably and efficiently.
文摘The interest in tailoring light in all its degrees of freedom is steadily gaining traction,driven by the tremendous developments in the toolkit for the creation,control and detection of what is now called structured light.Because the complexity of these optical fields is generally understood in terms of interference,the tools have historically been linear optical elements that create the desired superpositions.For this reason,despite the long and impressive history of nonlinear optics,only recently has the spatial structure of light in nonlinear processes come to the fore.In this review we provide a concise theoretical framework for understanding nonlinear optics in the context of structured light,offering an overview and perspective on the progress made,and the challenges that remain.
基金Project supported by the Science and Technology Major Projects of Zhejiang Province,China(Grant No.2013C03043-5)
文摘Digital structured light (SL) profilometry is increasingly used in three-dimensional (3D) measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.
基金This research work is supported by the National Natural Science Foundation of China under Grant No. 51175119.
文摘In order to realize the closed-loop control for rapid prototyping process based on gas metal arc welding, the geometric parameters of weld beads should be detected. In this study, a vision sensor system consisting of a linear laser projector and a CCD camera was designed to collect images of weld beads. Then, an image processing approach which combines with a Gaassian filter and an improved gravity method was used to extract the centerline of a light stripe based on VC ++. Feature points of the centerline were identical directly by means of an image fusion algorithm. Experimental results show that image fusion is an effective approach to measure the width and height of the weld bead with high accuracy. This method can identify beads effectively in multi-pass welding and avoid designing different modes to suit all kinds of shapes.
基金funded by Scientific and Technological Projects of Henan Province under Grant 182102210065Key Scientific Research Projects of Henan Universities under Grant 15A413015.
文摘Three-dimensional(3D)reconstruction using structured light projection has the characteristics of non-contact,high precision,easy operation,and strong real-time performance.However,for actual measurement,projection modulated images are disturbed by electronic noise or other interference,which reduces the precision of the measurement system.To solve this problem,a 3D measurement algorithm of structured light based on deep learning is proposed.The end-to-end multi-convolution neural network model is designed to separately extract the coarse-and fine-layer features of a 3D image.The point-cloud model is obtained by nonlinear regression.The weighting coefficient loss function is introduced to the multi-convolution neural network,and the point-cloud data are continuously optimized to obtain the 3D reconstruction model.To verify the effectiveness of the method,image datasets of different 3D gypsum models were collected,trained,and tested using the above method.Experimental results show that the algorithm effectively eliminates external light environmental interference,avoids the influence of object shape,and achieves higher stability and precision.The proposed method is proved to be effective for regular objects.
文摘A 3D surface reconstruction method using a binocular stereo vision technology and a coded structured light,which combines a gray code with phase-shift has been studied.The accuracy of the 3 D surface reconstruction mainly depends on the decoding of gray code views and phase-shift views.In order to find the boundary accurately,gray code patterns and their inverses are projected onto a human eye plaster model.The period dislocation between the gray code views and the phase-shift views in the course of decoding has been analyzed and a new method has been proposed to solve it.The splicing method is based on feature points.The result of the 3D surface reconstruction shows the accuracy and reliability of our method.
基金Project supported by the National Natural Science Foundation of China (Grant No.60772124)the State Key Program of National Natural Science of China (Grant No.60832003)+1 种基金the Shanghai Leading Academic Discipline Project (Grant No.S30108)the Foundation of the Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2231100)
文摘M-arrays are random arrays in which an appropriate sub-window appears only once in the whole array. Coded structured light based on M-arrays is one=shot technique to rapidly acquire 3D information of unknown surfaces by projecting suitable patterns onto a measuring surface. This paper presents a method to construct large size M-arrays based on the piece growing algorithm in which an array is constructed by many pieces through splicing each other. Reconstructing 3D shapes by utilizing the designed pattern based on constructed M-arrays for two objects are given.
基金This project is supported by National Natural Science Foundation of China (No.50275120, No.50535030)Great Science and Technology Project of Xi'an City, China(No.CX200206)
文摘Aiming at the problem that the existence of disturbances on the edges of light-stripe makes the segmentation of the light-stripes images difficult, a new segmentation algorithm based on edge-searching is presented. It firstly calculates every edge pixel's horizontal coordinate grads to produce the corresponding grads-edge, then uses a designed length-variable l D template to scan the light-stripes' grads-edges. The template is able to find the disturbances with different width utilizing the distributing character of the edge disturbances. The found disturbances are eliminated finally. The algorithm not only can smoothly segment the light-stripes images, but also eliminate most disturbances on the light-stripes' edges without damaging the light-stripes images' 3D information. A practical example of using the proposed algorithm is given in the end. It is proved that the efficiency of the algorithm has been improved obviously by comparison.
基金This project is supported by National Natural Science Foundation ofChina (No.50375047).
文摘A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway groove by a DLP projector, and distorting of stripes is happened on the raceway. Simultaneously, aided by three-step phase-shifting approach, three images covered by different stripes are obtained by a high-resolution CCD camera at the same location, thus a more accuracy local topography can be obtained. And then the bearing is rotated on a high precision computer controlled rotational stage. Three images are also obtained as the former step at next planned location triggered by the motor. After one cycle, all images information is combined through the mosaics. As a result, the 3D information of raceway groove can be gained. Not only geometric properties but also surface flaws can be extracted by software. A preliminary hardware system has been built, with which some geometric parameters have been extracted from reconstructed local topography.
文摘Measurement of out-of-plane deformation is significant to understanding of the deflection mechanisms of the plate and tube structures.In this study,a new surface contouring technique with color structured light is applied to measure the out-of-plane deformation of structures with one-shot projection.Through color fringe recognizing,decoding and triangulation processing for the captured images corresponding to each deformation state,the feasibility of the method is testified by the measurement of elastic deflections of a flexible square plate,showing good agreement with those from the calibrated displacement driver.The plastic deformation of two alloy aluminum rectangular tubes is measured to show the technique application to surface topographic evaluation of the buckling structures with large displacements.
基金Supported by the National Natural Science Foundation of China(61273346)the National Defense Key Fundamental Research Program of China(A20130010)the Program for the Fundamental Research of Beijing Institute of Technology(2016CX02010)
文摘Since unmanned ground vehicles often encounter concave and convex obstacles in wild ground, a filtering algorithm using line structured light to detect these long distance obstacles is proposed. For the line structured light image, a ranked-order based adaptively extremum median (RAEM) filter algorithm on salt and pepper noise is presented. In the algorithm, firstly effective points and noise points in a filtering window are differentiated; then the gray values of noise points are replaced by the medium of gray values of the effective pixels, with the efficient points' gray values unchanged; in the end this algorithm is proved to be efficient by experiments. Experimental resuits demonstrate that the image blur, resulting into proposed algorithm can remove noise points effectively and minimize the protecting the edge information as much as possible.
基金supports from National Natural Science Foundation of China (No.62235009).
文摘Spatial light modulators,as dynamic flat-panel optical devices,have witnessed rapid development over the past two decades,concomitant with the advancements in micro-and opto-electronic integration technology.In particular,liquid-crystal spatial light modulator(LC-SLM)technologies have been regarded as versatile tools for generating arbitrary optical fields and tailoring all degrees of freedom beyond just phase and amplitude.These devices have gained significant interest in the nascent field of structured light in space and time,facilitated by their ease of use and real-time light manipulation,fueling both fundamental research and practical applications.Here we provide an overview of the key working principles of LC-SLMs and review the significant progress made to date in their deployment for various applications,covering topics as diverse as beam shaping and steering,holography,optical trapping and tweezers,measurement,wavefront coding,optical vortex,and quantum optics.Finally,we conclude with an outlook on the potential opportunities and technical challenges in this rapidly developing field.
文摘Behavior of structure light is investigated by monitoring probe absorption using a microwave-driven Y-type atomic media configuration.The system under consideration is driven by one of the control vortex beams as well as an extra non-vortex control beam to ensure electromagnetically induced transparency.The significant aspect in the generation of structured light is the azimuthal phase-dependent modification for probe absorption.Further intensity distribution for absorption spectra is examined for simultaneously evaluating both the control vortex beams.We also go through the radial distribution of intensity for various orbital angular momentum values.Different modes of structural beams may be distinguished using the suggested approach.Our research gives us a way for rapidly transferring vortex wavefronts from control field to probe absorption profile.This could be useful in quantum information processing.
基金This work was supported by the National Natural Science Foundation of China(Nos.51878354&51308301)the Natural Science Foundation of Jiangsu Province(Nos.BK20181402&BK20130978)333 Talent High-Level Project of Jiangsu Province,and Qinglan Project of Jiangsu Higher Education Institutions.Any research results expressed in this paper are those of the writer(s)and do not necessarily reflect the views of the foundations.
文摘Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more development opportunities.As an indispensable part of light wood structure systems,the wood-frame shear wall plays a vital role in the bearing capacity and earthquake resistance of light wood structure systems.This paper is focused on a review of the lateral performance of wood-frame shear walls and classifies the influencing factors in relevant experimental research into three categories,including internal factors such as shear wall structure,external factors such as test scheme,and other factors of material production and test process.Finally,the research prospects in this field were introduced based on the summary of the research status.This work can be a reference for further research on the lateral performance of wood-frame shear walls.
文摘In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction;thus they provide technical and cost advantages. The insitu laser machining system realizes a simple operation process by integrating measurement and machining,which greatly reduces labor and time costs.
文摘3D reconstruction of worn parts is the foundation for remanufacturing system based on robotic arc welding, because it can provide 3D geometric information for robot task plan. In this investigation, a novel 3D reconstruction system based on linear structured light vision sensing is developed. This system hardware consists of a MTC368-CB CCD camera, a MLH-645 laser projector and a DH-CG300 image grabbing card. This system software is developed to control the image data capture. In order to reconstruct the 3D geometric information from the captured image, a two steps rapid calibration algorithm is proposed. The 3D reconstruction experiment shows a satisfactory result.
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2007AA11Z130)
文摘In the present study,the formula calculating ship impact forces on light wharf structures is presented when the elastic deformation of the hull and the pier structures as well as the nonlinear deformation of the fender are taken into account. The ship impact forces are statistically analyzed with the Monte-Carlo method according to the known probability distribution types of random variables.Based on the simulated results, the distribution of ship impact forces which is characterized by bimodal distribution can be expressed as the combining probability density function of beta distribution and normal distribution. The corresponding parameters of the probability density function can be estimated with the maximum likelihood method. The results show that ship impact forces on light wharf structures follow the distribution of type I extreme value.The mean coefficient and variation coefficient are 1.11 and 0.008 respectively during 50 years of design reference period.
基金the National Research Foundation and the CSIR-NRF Rental Pool Program.
文摘Structured light is routinely used in free-space optical communication channels,both classical and quantum,where information is encoded in the spatial structure of the mode for increased bandwidth.Both real-world and experimentally simulated turbulence conditions have revealed that free-space structured light modes are perturbed in some manner by turbulence,resulting in both amplitude and phase distortions,and consequently,much attention has focused on whether one mode type is more robust than another,but with seemingly inconclusive and contradictory results.We present complex forms of structured light that are invariant under propagation through the atmosphere:the true eigenmodes of atmospheric turbulence.We provide a theoretical procedure for obtaining these eigenmodes and confirm their invariance both numerically and experimentally.Although we have demonstrated the approach on atmospheric turbulence,its generality allows it to be extended to other channels too,such as aberrated paths,underwater,and in optical fiber.
基金This research was supported by the National Key R&D Program of China(No.2019YFD0901302)the National Natural Science Foundation of China(No.31802349).
文摘The creation of three-dimensional models from an unorganized set of points is an active research area in computer graphics.One of the purposes of this study is to explore the 3D reconstruction of a cube-type artificial reef(CTAR)set by linear structured light and binocular stereo vision technology in an underwater environment.The experimental setup is composed of two ca-meras in a stereo vision configuration.The alpha shapes method can be used to construct a surface that most closely reflects the arti-ficial reef set described by the points.A parameter study is conducted to assess the scales of the set(i.e.,usable volume,surface area,projected area,height,and base diameter)on the basis of 3D reconstruction.Experimental results show that the quality of 3D recon-struction in an underwater environment is acceptable for estimating the scale size of the CTAR set.According to the measurement of the scale sizing of the CTAR set,the relationships between the parameters of the CTAR set and the number of CTAR modules were determined.Moreover,the usable volume of the CTAR set can be estimated depending on the basis of the number of CTAR modules.
基金This work was supported by Henan Province Science and Technology Project under Grant No.182102210065.
文摘The binocular stereo vision system is often used to reconstruct 3D point clouds of an object.However,it is challenging to find effective matching points in two object images with similar color or less texture.This will lead to mismatching by using the stereo matching algorithm to calculate the disparity map.In this context,the object can’t be reconstructed precisely.As a countermeasure,this study proposes to combine the Gray code fringe projection with the binocular camera as well as to generate denser point clouds by projecting an active light source to increase the texture of the object,which greatly reduces the reconstruction error caused by the lack of texture.Due to the limitation of the camera viewing angle,a one-perspective binocular camera can only reconstruct the 2.5D model of an object.To obtain the 3D model of an object,point clouds obtained from multiple-view images are processed by coarse registration using the coarse SAC-IA algorithm and fine registration using the ICP algorithm,which is followed by voxel filtering fusion of the point cloud.To improve the reconstruction quality,a polarizer is mounted in front of the cameras to filter out the redundant reflected light.Eventually,the 3D model and the dimension of a vase are obtained after calibration.