Acquisition Of 3D Information Research Articles

THEORETICAL ACCURACY PREDICTION AND VALIDATION OF LOW-END AND HIGH-END MOBILE MAPPING SYSTEM IN URBAN, RESIDENTIAL AND RURAL AREAS

Abstract. Mobile mapping systems are increasingly being used for the acquisition of 3D information of the environment. Although these systems are very efficient in data capturing compared to more traditional methods, the high cost of high-end accurate mobile mapping systems is a major drawback. In contrast, the much cheaper low-end mobile mapping systems are more frequently used for less accurate projects where visualization is more important. In general, the achievable accuracy level is the driving factor that differentiates low-end from high-end systems. To determine this value, the sensor quality, calibration and GNSS reception quality should be reliably evaluated.In this paper, we present a theoretical accuracy model of a mobile mapping system that takes into account variable GNSS accuracy. The predicted accuracy level of low-end and high-end mobile mapping systems is evaluated in a comprehensive accuracy analysis. The absolute accuracy of the system is determined in three datasets in which GNSS reception quality varies between optimal, good and poor. Additionally, the relative accuracy of both systems is checked by comparison of control distances. The presented approach allows for a more general and robust accuracy prediction of mobile mapping systems in different circumstances.

마이크로 스케일 물체의 3차원 정보 획득을 위한 구조 조명 현미경 최적화 기술

최근, 가상현실 기기와 콘텐츠 제작 기술의 발전으로 유명 유적이나 관광지를 3차원 실사로 구현하여 원격으로 체험할 수 있게 되었다. 미시세계를 가상현실로 구현하기 위해서는 실사하는 것이 가장 좋은 방법이다. 본 논문에서는 마이크로 스케일을 갖는 물체의 3차원 정보를 획득하기 위한 구조 조명 현미경 최적화 기술에 대해 다루고자 한다. 구조 조명 현미경 (Structured illumination microscopy, SIM)은 흐려짐을 줄이고 축 해상도를 증가시킬 수 있는 광학 단면 기술을 사용하는 3 차원 측정 방법 중 하나이다. 이때, 최대 단면 강도는 정규화 공간 주파수가 1인 격자 패턴을 사용하여 수행되었으며, 적절한 고공간 주파수 격자 패턴에 의해 광학 단면을 최적화하여 미시세계를 실사화 할 수 있었다.

3D Surface Matching by a Voxel-Based Buffer-Weighted Binary Descriptor

3D surface matching by local feature descriptors is a fundamental task in 3D object registration, recognition, and retrieval. In view of 2D projected descriptors’ information compression and 3D directly voxelized descriptors’ sensitivity to density variation and boundary, this paper first proposes a voxel-based buffer-weighted binary descriptor, named VBBD. After local surfaces of detected keypoints are voxelized, each voxel’s buffer region is established, and the buffer-weighted Gaussian kernel density is calculated. If the current voxel’s buffer-weighted density is larger than its local surface’s average density, the voxel is labeled 1, otherwise, it is 0. The proposed descriptor has several merits: 1) direct acquisition of 3D information without projection, the neighbor information is less compressed. 2) voxels are labeled and binarized according to the buffer-weighted density, which improves the robustness to boundary effect, noise and density variation. Based on the VBBD, a global optimal surface matching method based on a Kuhn_Munkres (KM) algorithm is adopted. The strategy has several advantages: 1) by calculating the descriptors of large-scaled surfaces which are down sampled, the number of the point cloud is reduced, and meanwhile, large-scaled information is obtained; and 2) KM algorithm is adopted to find matching pairs to achieve final maximum weight sum of all matching pairs, which can efficiently avoid local optimum. The experimental results show that, compared with other state-of-the-art descriptors, the VBBD has better descriptiveness and robustness, and the surface matching strategy by the VBBD can achieve both high recall and precision.

Design of the Fall-Block Sensing of the Railway Line Pantograph Based on 3D Machine Vision Sensors.

As an important part of the electric locomotive in railway transportation, the sensing and inspection of the pantograph has a significant effect on the safe operation of the train. In general, the pantograph carbon slip detection items include slide wear detection, slip strip crack detection, carbon slip fall-block detection and slip strip wear detection. The emergence and development of structured light measurement technology with 3D sensors provide new technical means for the acquisition of spatial 3D information. The three-dimensional data can not only obtain more information but also reduce the data deviation, thereby improving the measurement accuracy and work efficiency. At present, few studies have been conducted on the slide block and partial wear of the carbon slide. Therefore, this paper studies the detection of the pantograph slide block based on 3D sensor measurement technology. The experimental results indicate that it is feasible to adopt 3D measurement technology to detect the fall-block of the pantograph slide. In addition, a sound detection effect can also be obtained.

基于TOF计算成像的三维信息获取与误差分析

基于TOF计算成像的三维信息获取与误差分析

3D image scanning microscopy with engineered excitation and detection

Scanning microscopes are important research tools for investigating 3D specimens. Modern beam shaping techniques can be combined with suitably designed data processing algorithms to improve instrument versatility and imaging performance. Here we introduce image scanning microscopy with freely programmable excitation and detection pupils and investigate point spread function (PSF) designs for parallel 3D information acquisition. The volumetric data is collected in a single 2D scan without the requirement of physical refocus. By sculpturing the excitation and detection PSFs into helical shapes of opposing handedness, we are able to capture sample information in a volume whose axial extension measures more than four times the z resolution. In a more generalized approach, jointly optimized phase masks are used in both pupils to shape the PSFs. As an exemplary case, we study the use of beam-splitting phase masks for the parallel scanning in multiple planes. The image reconstruction algorithm optimally integrates this information according to the various signal-to-noise ratios. Generalized PSF engineering scanning systems provide resolution improvement relative to confocal microscopy while accelerating data collection. We analyze the opportunities, trade-offs, and limitations of the approach.

A theoretical 2D image model for locating 3D targets

ABSTRACTTo construct a water quality monitoring system, challenging issues need to be addressed regarding the acquisition of target information (e.g. 3D location and occlusion) as well as the behavioural analysis of aquatic organisms. This paper presents a novel 3D information acquisition and location method, by means of an information acquisition platform consisting of a monitoring terminal, frame grabbers, a single camera and a single mirror. Using this platform, we propose a theoretical 2D image model for locating 3D targets and then validate it using data obtained from both real and artificial fish. The proposed model is based on the principles of light refraction, plane mirror imaging, underwater objects and camera imaging as well as the technologies of digital to analog conversion and object segmentation. In contrast with existing methods, our method can accurately reflect 3D information of aquatic organisms, thus providing critical technical support for the development of water quality monitoring systems in the future.

In vivo tooth-color measurement with a new 3D intraoral scanning system in comparison to conventional digital and visual color determination methods.

Three-dimensional (3D) intraoral scanning systems allow for the simultaneous acquisition of 3D information about tooth surfaces and a photorealistic view of the patient's tooth colors. The goal of this study was the in vivo comparison of a new 3D scanner with a color acquisition mode and conventional visual and digital color measurements. The colors of 40 teeth of 20 patients were evaluated in seven ways: 1) By dentists using the Vita 3D-Master; 2) By dental technicians using the Vita 3D-Master; 3) With the 3Shape Trios device; 4) With the Vita Easyshade device; 5) With the Vita Easyshade Advance device; 6) With the SpectroShade device; and 7) With the SpectroShade Micro device. Digital measurements of Groups 3 to 7 were repeated three times for each tooth. For all groups, both the CIE Lab values and the Vita 3D-Master values were recorded. The repeatability and relative accuracy of the Vita 3D-Master values were analyzed statistically using Pearson's chi-squared test (α < 0.05). ΔE values were calculated from the CIE Lab values, which served as a basis for performing multidimensional scaling (MDS) and evaluating differences between the groups using the one-way ANOVA with post hoc Tamhane's test (α < 0.05). The results of the ΔE values showed that clinically relevant differences between the evaluation by dentists, dental technicians, and the intraoral scanning device (3Shape) are negligible. The intraoral 3D scanning device (Group 3) and the digital systems (Groups 4 to 7) did not differ significantly in the repeatability of color shade management. The SpectroShade Micro (Group 7) had significantly better relative accuracy than the other devices. The results demonstrate that intraoral scanning systems can be used to measure both tooth color and tooth surface in 3D. Intraoral optical scanning devices allow for the acquisition of accurate 3D surface data. Tooth color can be evaluated simultaneously and can be used to determine the color of restorations without requiring additional conventional color-measurement methods.

3D inspection technology combining passive stereo matching and active structured light for steel plate surface sample

Three-dimensional (3D) inspection technology is a new important research hotspot in the field of steel surface defect inspection. However, current 3D information acquisition methods (i.e., the passive stereo vision method and active structured light method) still suffer from several issues. In order to solve these issues, a three-dimensional inspection system is designed in this paper. In this system, the passive stereo vision method and active structured light method are combined to obtain the surface sample height information of high temperature steel plate. Furthermore, the Hexagonal grid Census (Hg_Census) transform is proposed to improve the robustness of census transform stereo matching. Moreover, the passive stereo disparity map is adopted as a constraint condition to realise phase matching using wrapped phase. In addition, the local phase matching and sub-pixel disparity refinement are proposed to obtain high measuring accuracy. Three high temperature steel plate surface samples are picked to verify the effectiveness of the proposed method. The actual experimental results present the average error is less than 1 mm.

3D inspection technology combining passive stereo matching and active structured light for steel plate surface sample

Three-dimensional (3D) inspection technology is a new important research hotspot in the field of steel surface defect inspection. However, current 3D information acquisition methods (i.e., the passive stereo vision method and active structured light method) still suffer from several issues. In order to solve these issues, a three-dimensional inspection system is designed in this paper. In this system, the passive stereo vision method and active structured light method are combined to obtain the surface sample height information of high temperature steel plate. Furthermore, the Hexagonal grid Census (Hg_Census) transform is proposed to improve the robustness of census transform stereo matching. Moreover, the passive stereo disparity map is adopted as a constraint condition to realise phase matching using wrapped phase. In addition, the local phase matching and sub-pixel disparity refinement are proposed to obtain high measuring accuracy. Three high temperature steel plate surface samples are picked to verify the effectiveness of the proposed method. The actual experimental results present the average error is less than 1 mm.

Street-side vehicle detection, classification and change detection using mobile laser scanning data

Statistics on street-side car parks, e.g. occupancy rates, parked vehicle types, parking durations, are of great importance for urban planning and policy making. Related studies, e.g. vehicle detection and classification, mostly focus on static images or video. Whereas mobile laser scanning (MLS) systems are increasingly utilized for urban street environment perception due to their direct 3D information acquisition, high accuracy and movability. In this paper, we design a complete system for car park monitoring, including vehicle recognition, localization, classification and change detection, from laser scanning point clouds. The experimental data are acquired by an MLS system using high frequency laser scanner which scans the streets vertically along the system’s moving trajectory. The point clouds are firstly classified as ground, building façade, and street objects which are then segmented using state-of-the-art methods. Each segment is treated as an object hypothesis, and its geometric features are extracted. Moreover, a deformable vehicle model is fitted to each object. By fitting an explicit model to the vehicle points, detailed information, such as precise position and orientation, can be obtained. The model parameters are also treated as vehicle features. Together with the geometric features, they are applied to a supervised learning procedure for vehicle or non-vehicle recognition. The classes of detected vehicles are also investigated. Whether vehicles have changed across two datasets acquired at different times is detected to estimate the durations. Here, vehicles are trained pair-wisely. Two same or different vehicles are paired up as training samples. As a result, the vehicle recognition, classification and change detection accuracies are 95.9%, 86.0% and 98.7%, respectively. Vehicle modelling improves not only the recognition rate, but also the localization precision compared to bounding boxes.

Automatic Registration of Two Parts using Robot with Multiple 3D Sensor Systems

In this paper, we propose an algorithm for the automatic registration of two rigid parts using multiple 3D sensor systems on a robot. Four sets of structured laser stripe system consisted of a camera and a visible laser stripe is used for the acquisition of 3D information. Detailed procedures including extrinsic calibration among four 3D sensor systems and hand/eye calibration of 3D sensing system on robot arm are presented. We find a best pose using search-based pose estimation algorithm where cost function is proposed by reflecting geometric constraints between sensor systems and target objects. A pose with minimum gap and height difference is found by greedy search. Experimental result using demo system shows the robustness and feasibility of the proposed algorithm.

Discontinuity spacing analysis in rock masses using 3D point clouds

The complete characterization of rock masses implies the acquisition of information of both, the materials which compose the rock mass and the discontinuities which divide the outcrop. Recent advances in the use of remote sensing techniques – such as Light Detection and Ranging (LiDAR) – allow the accurate and dense acquisition of 3D information that can be used for the characterization of discontinuities.This work presents a novel methodology which allows the calculation of the normal spacing of persistent and non-persistent discontinuity sets using 3D point cloud datasets considering the three dimensional relationships between clusters. This approach requires that the 3D dataset has been previously classified. This implies that discontinuity sets are previously extracted, every single point is labeled with its corresponding discontinuity set and every exposed planar surface is analytically calculated. Then, for each discontinuity set the method calculates the normal spacing between an exposed plane and its nearest one considering 3D space relationship. This link between planes is obtained calculating for every point its nearest point member of the same discontinuity set, which provides its nearest plane. This allows calculating the normal spacing for every plane. Finally, the normal spacing is calculated as the mean value of all the normal spacings for each discontinuity set.The methodology is validated through three cases of study using synthetic data and 3D laser scanning datasets. The first case illustrates the fundamentals and the performance of the proposed methodology. The second and the third cases of study correspond to two rock slopes for which datasets were acquired using a 3D laser scanner. The second case study has shown that results obtained from the traditional and the proposed approaches are reasonably similar. Nevertheless, a discrepancy between both approaches has been found when the exposed planes members of a discontinuity set were hard to identify and when the planes pairing was difficult to establish during the fieldwork campaign. The third case study also has evidenced that when the number of identified exposed planes is high, the calculated normal spacing using the proposed approach is minor than those using the traditional approach.

Valid point detection in fringe projection profilometry.

Fringe projection profilometry has become one of the most popular 3D information acquisition techniques being developed over the past three decades. However, the general and practical issues on valid point detection, including object segmentation, error correction and noisy point removal, have not been studied thoroughly. Furthermore, existing valid point detection techniques require multiple case-dependent thresholds which increase processing inconvenience. In this paper, we proposed a new valid point detection framework, which includes the k-means clustering for automatic background segmentation, unwrapping error correction based on theoretical analysis, and noisy point detection in both temporal and spatial directions with automatic threshold setting. Experimental results are given to validate the proposed framework.

Automatic Manipulation of Tie Rod using Robot with 3D Sensing System

Robots are widely used in various automation processes in industrial applications. Traditionally, it operated under fixed condition by teaching operating positions. Recently, diverse 2D/3D sensors are used together with robot to give more flexibility in operation. In this paper, we deal with automatic manipulation of tie rod in automotive production line. Sensor system consisted of a camera and slit laser is used for the acquisition of 3D information and it is used attached on the robot. Nut runner is used for the manipulation of stop nut and adjust bolt on the tie rod. Detailed procedures for the automatic manipulation of tie rod are presented. In the presented approach, we effectively use 3D information in whole procedure such as computing distance to the tie rod, rotation angle of bolt and nut. Experimental results show the feasibility of the proposed algorithm.

핀홀 스테레오 비전 센서의 공간 스캔을 통한 방사선의 영상화 시뮬레이션

There are always much concern about the leakage of radiation materials in the event of dismantle or unexpected accident of nuclear power plant. In order to remove the leakage of radiation materials, appropriate dispersion detection techniques for radiation materials are necessary. However, because direct handling of radiation materials is highly restricted and risky, developing radiation-related techniques needs computer simulation in advance to evaluate the feasibility. In this paper, we propose a radiation imaging technique which can acquire 3D dispersion information of radiation materials and tested by simulation. Using two virtual 1D radiation sensors, we obtain stereo radiation images and acquire the 3D depth to virtual radiation materials using stereo disparity. For point and plane type virtual radiation materials, the possibility of the acquisition of stereo radiation image and 3D information are simulated.

3D seismic processing and interpretation from 2D seismic data: Application in environmentally sensitive areas of the Neuquén Basin, Argentina

The increasing environmental and regulatory restrictions for recording 3D seismic, along with urban constraints, are limiting the acquisition of new 3D seismic information in some areas. A low-cost methodology can provide a pseudo-3D seismic data set. Geologic complexity is the most important condition to understand to assess the quality of the pseudo-3D volume created. These data can help to reduce many structural uncertainties that can be solved geometrically or at least outlined, giving real improvement in evaluation of prospective areas or in delineation of fields and generating new drilling strategies. In addition, the generated 3D data can be used as input for seismic-attribute calculation that otherwise would not have been possible because of discrete 2D information. The technique basically consists of conducting prestack migration using 24 offset planes, limiting with a structure control, and using the spatial propagation of the migration operator. The results of this data treatment show a homogeneous and consistent distribution of each processing attribute.

An Improved Gaussian Fitting Method Used in Light-Trap Center Acquiring

In the 3D measurement based on line-structured light projection, the accuracy of center position of the stripe is of great importance for that of the 3D information acquisition system. A method of sub-pixel center-extracted that in the level of sub-pixel were discussed by He Jun-ji. Based on it and considered the fact that light intensity of the stripes center presents a Gaussian distribution status approximately, in this paper, a new method for extracting stripe center line has been proposed. The extracting curve is closer to the ideal value, and can efficiently extracted the center-line of light stripe, and the accuracy of 3D reconstruction is improved.

Highway three-dimensional modeling based on Vehicle-borne laser data

The of Vehicle-borne LiDAR (Light Detection And Ranging) scanning technology is an efficiently practical approach on the acquisition and application of 3D information and its geographic elements of highway(including road surface, rails, attached facilities, slopes, ditches, etc.). The acquired information is significant on many aspects such as road maintenance, reconstruction, survey, landscape design, visualized modelling and highway hazard supervision and prevention. The initial laser data cannot be directly used to construct highway 3D model, operations of pre-processing are necessary. This paper presented a set of procedure about pre-processing laser data and constructing TIN (Triangle Irregular Net) model of highway.

Precise calibration of a rotation photogrammetric system

Rotation photogrammetric systems are widely used for 3D information acquisition, where high-precision calibration is one of the critical steps. This study first shows how to derive the rotation model and deviation model in the object space coordinate system according to the basic structure of the system and the geometric relationship of the related coordinate systems. Then, overall adjustment of multi-images from a surveying station is employed to calibrate the rotation matrix and the deviation matrix of the system. The exterior orientation parameters of images captured by other surveying stations can be automatically calculated for 3D reconstruction. Finally, real measured data from Wumen wall of the Forbidden City is employed to verify the performance of the proposed calibration method. Experimental results show that this method is accurate and reliable and that a millimetre level precision can be obtained in practice.