3D Measurement System Research Articles

Combining laser transformation hardening and ultrasonic impact strain hardening for enhanced wear resistance of AISI 1045 steel

A medium-carbon steel AISI 1045 was hardened by a laser heat treatment (LHT), a multi-pin ultrasonic impact treatment (UIT), and two combined laser-ultrasonic surface treatments (UIT + LHT and LHT + UIT processes) to improve the wear resistance of the surface layer. The paper is focused on detecting the relationship between the surface roughness and microstructure, phase state, hardness, residual stress of the specimens hardened by the LHT, UIT and combined UI + LHT/LHT + UIT processes, and their wear and friction behaviors. The hardened plane specimens were examined after the short-term (15 min) and long-term (45 min) wear tests under oil-lubricated conditions in the quasi-static and dynamic loads. The analysis of the surface morphologies and cross-section profiles of the worn tracks were assessed by an optical 3D measurement system and scanning electron microscopy (SEM). The wear mechanisms are also discussed. Results showed that the combined LHT + UIT treatment provides a lower surface roughness (Ra ~0.25 μm) and a highest surface hardness (~11,000 HV0.05) while the combined UIT + LHT treatment leads to the deeper hardened zone by 1.5–2 times. As compared to the untreated specimen (dynamic tests), the wear loss magnitudes were respectively decreased by ~5%, 35%, 42%, and 84% after the UIT, LHT, combined UIT + LHT and LHT + UIT processes. The LHT + UIT-processed specimen has the highest wear resistance owing to the formation of the fine-grained martensitic microstructure, more flattened surface microrelief, and the absence of the oxide film.

Self-calibration for linear structured light 3D measurement system based on quantum genetic algorithm and feature matching

In this paper, a self-calibration method for a linear structured light 3D measurement system and its advantages are presented. According to the mathematical model of the linear-structured light 3D measurement system, the calibration problem is a highdimensional optimization problem. The principle of this self-calibration method can be drawn from a traditional calibration method. In this method, quantum genetic algorithm and feature matching are applied to self-calibration. Feature matching is used to derive two points with fixed spatial relationships, and an optimal solution of system parameters can be obtained by quantum genetic algorithm. Finally, experimental results are given. The measurement error is 0.05 mm and the ratio of the error to scanning distance is 1.54e-4.In this paper, a self-calibration method for a linear structured light 3D measurement system and its advantages are presented. According to the mathematical model of the linear-structured light 3D measurement system, the calibration problem is a high-dimensional optimization problem. The principle of this self-calibration method can be drawn from a traditional calibration method. In this method, quantum genetic algorithm and feature matching are applied to selfcalibration. Feature matching is used to derive two points with fixed spatial relationships, and an optimal solution of system parameters can be obtained by quantum genetic algorithm. Finally, experimental results are given. The measurement error is 0.05 mm and the ratio of the error to scanning distance is 1.54e-4.

Development of underwater 3D shape measurement system with improved radiation tolerance

When performing remote tasks using robots in nuclear power plants, a 3D shape measurement system is advantageous in improving the efficiency of remote operations by easily identifying the current state of the target object for example, size, shape, and distance information. Nuclear power plants have high-radiation and underwater environments therefore the electronic parts that comprise 3D shape measurement systems are prone to degradation and thus cannot be used for a long period of time. Also, given the refraction caused by a medium change in the underwater environment, optical design constraints and calibration methods for them are required. The present study proposed a method for developing an underwater 3D shape measurement system with improved radiation tolerance, which is composed of commercial electric parts and a stereo camera while being capable of easily and readily correcting underwater refraction. In an effort to improve its radiation tolerance, the number of parts that are exposed to a radiation environment was minimized to include only necessary components, such as a line beam laser, a motor to rotate the line beam laser, and a stereo camera. Given that a signal processing circuit and control circuit of the camera is susceptible to radiation, an image sensor and lens of the camera were separated from its main body to improve radiation tolerance. The prototype developed in the present study was made of commercial electric parts, and thus it was possible to improve the overall radiation tolerance at a relatively low cost. Also, it was easy to manufacture because there are few constraints for optical design.

Understanding Sex Differences in Children’s Injury Risk as Pedestrians

Boys experience more injuries as pedestrians than girls. The aim of this study was to compare how boys and girls cross streets in order to identify factors that differentially influence their injury risk as pedestrians. Using a fully immersive virtual reality (VR) system interfaced with a 3D movement measurement system, various measures of children's street-crossing behaviors were taken. At the start of the crossing, boys selected smaller (riskier) inter-vehicle gaps to cross into than girls. Subsequently, as they crossed, they showed greater attention to traffic, shorter start delay, and more evasive action than girls, which are strategies that could reduce risk as a pedestrian. Despite these efforts, however, boys experienced more hits and close calls than girls. To enhance their safety as pedestrians, girls adopt a proactive approach and select larger inter-vehicle gaps to cross into, whereas boys apply a reactive approach aimed at managing the risk created by having selected smaller (riskier) gaps. Girls' proactive approach yielded safer outcomes than boys' reactive strategy.

A low-cost three-dimensional reconstruction and monitoring system using digital fringe projection

In this paper, the design and construction of a low-cost three-dimensional (3D) reconstruction and monitoring system using digital fringe projection (DFP) is proposed, which can perform small- and large-scale measurements in different environments and can be applied to various applications such as intelligent monitoring, 3D online inspection, and obstacle detection for vehicle guidance. The contribution of this paper is threefold: (i) development of a comprehensive 3D measuring system that performs sensors handling, coordinate acquisition, reconstruction, and display process simultaneously and quickly; (ii) proposal of new filters to improve quality and efficiency of the system; and (iii) development of a real-time virtual 3D measurement system to calibrate and analyze the proposed methodologies. Optical and simulation measurement results are presented to verify the feasibility and performance of the developed systems. The observed RMS difference was found to be <0.021 mm in the optical measurement. From measured results, it can be concluded that the proposed systems and adopted methodology are effective in obtaining 3D surface profiles.

OPTICAL 3D MEASUREMENTS IN HYDRODYNAMIC TUNNEL FOR AIRCRAFT ICING STUDY

Abstract. The study of how aircraft icing influences on aircraft aerodynamic performance is very important for developing measures and recommendation to improve aircraft flight safety. The effective method of aerodynamic processes modeling is experiment in wind (aerodynamic) tunnel or water (hydrodynamic) tunnel. They allow to perform experiments with a scaled model of an aircraft affected by icing and to visualize the wing flow process and changes caused by icing. While visualization of the wing flow yields useful qualitative information about flow, it is more important to retrieve quantitative 3D data of flow, which allows to forecast icing process and to develop anti-icing techniques and recommendations.The presented study addresses to creating an photogrammetric system and 3D measurement techniques for quantitate evaluation of 3D flow parameters in a hydrodynamic tunnel for aircraft icing influence exploration. Being an initial part of a long-term research project, this study is aimed at developing of an accurate calibration technique of the photogrammetric system for 3D measurement in condition of two optical media interfaces. The developed algorithms for imaging process through two optical media interfaces are used in calibration procedure and object 3D coordinates measuring. The results of the photogrammetric system calibration are given in comparison with standard (single media) case. Experimental 3D reconstruction of a typical object demonstrated high accuracy of the developed algorithms.

Biomechanical comparison of fixation techniques for transverse acetabular fractures – Single-leg stance vs. sit-to-stand loading

ObjectivesTo biomechanically compare five different fixation techniques for transverse acetabular fractures using both the single-leg stance (SLS) and the sit-to-stand (STS) loading protocols and to directly compare fracture gap motion (FGM) and relative interfragmentary rotation (RIFR). MethodsTranstectal transverse acetabular fractures were created on fourth-generation composite hemipelves in a reproducible manner. Five different fixation techniques were biomechanically assessed using both an SLS and STS loading protocol: anterior plate (AP) only, posterior plate (PP) only, anterior plate plus posterior column screw (AP+PCS), posterior plate plus anterior column screw (PP+ACS) and anterior plus posterior plate (AP+PP). After preconditioning, the specimens were loaded from 50 to 750 N with a ramp of 100 N/s. FGM and RIFR under loads of 750 N were measured using an optical 3D measurement system. ResultsIn the three groups of fixation techniques addressing both columns, STS loading resulted in higher mean FGM and in RIFR than SLS loading. No construct failure was observed. In the single plate groups (AP only and PP only), STS loading resulted in failure of all specimens before reaching loads of 750 N, while no failure occurred after SLS loading. No significant differences in FGM and RIFR were found between the double plate (AP+PP) and the single plate plus column screw (AP+PCS and PP+ACS) techniques. ConclusionSLS loading appeared to overestimate the strength of acetabular fracture fixation constructs and STS loading may be more appropriate to provide clinically relevant biomechanical data. Internal fixation of a single column might not provide adequate stability for transverse fractures, while strength of single plate plus column screw fixation and double plate fixation was comparable.

DietSensor: Automatic Dietary Intake Measurement Using Mobile 3D Scanning Sensor for Diabetic Patients.

Diabetes is a global epidemic that impacts millions of people every year. Enhanced dietary assessment techniques are critical for maintaining a healthy life for a diabetic patient. Moreover, hospitals must monitor their diabetic patients’ food intake to prescribe a certain amount of insulin. Malnutrition significantly increases patient mortality, the duration of the hospital stay, and, ultimately, medical costs. Currently, hospitals are not fully equipped to measure and track a patient’s nutritional intake, and the existing solutions require an extensive user input, which introduces a lot of human errors causing endocrinologists to overlook the measurement. This paper presents DietSensor, a wearable three-dimensional (3D) measurement system, which uses an over the counter 3D camera to assist the hospital personnel with measuring a patient’s nutritional intake. The structured environment of the hospital provides the opportunity to have access to the total nutritional data of any meal prepared in the kitchen as a cloud database. DietSensor uses the 3D scans and correlates them with the hospital kitchen database to calculate the exact consumed nutrition by the patient. The system was tested on twelve volunteers with no prior background or familiarity with the system. The overall calculated nutrition from the DietSensor phone application was compared with the outputs from the 24-h dietary recall (24HR) web application and MyFitnessPal phone application. The average absolute error on the collected data was 73%, 51%, and 33% for the 24HR, MyFitnessPal, and DietSensor systems, respectively.

Research on 3D surface reconstruction and body size measurement of pigs based on multi-view RGB-D cameras

Body measurement is an important technique to acquire the livestock body parameters for precision agriculture and effective management of livestock. Traditionally, the livestock body parameters are often manually measured, which suffers from several drawbacks, including unstable accuracy, low efficiency, difficulty in measuring complex parameters, and potentially negative influence on animal welfare. Considering this, this paper presents a 3D surface reconstruction and body size measurement system based on multi-view RGB-D cameras. We use Kinect depth cameras to obtain the point clouds of the freely walking pigs from three different views (i.e., upper-view, left-view and right-view). The registration parameters are obtained by a rectangular cuboid, which can be used to reconstruct three local point clouds. Thereafter, the distribution of the point cloud projection in different directions is used to locate the measuring positions, which then contribute to the precise measurement of several key parameters, such as body length, body height, body width and abdominal girth. Moreover, the polar coordinate transform is developed to improve the measurement accuracy of the abdominal girth. The experiments performed on forty pigs have shown that our average relative errors in the body length, height, width and abdominal girth are 2.97%, 3.35%, 4.13% and 4.67%, respectively, which demonstrate the feasibility and accuracy of the proposed system.

A real-time 3D shape measurement with color texture using a monochromatic camera

High-speed real-time three-dimensional (3D) shape measurement with color texture has a large potential in various fields. The majority of the existing methods retrieve the 3D shape with color texture by employing an RGB camera or additional infrared camera; however, the RGB camera is more expensive and has lower sensitivity to light, and employing additional infrared camera requires complex alignment. Given this, a novel method is proposed to simultaneously retrieve the 3D shape and color texture. Specifically, compared with the existing methods, the proposed method only uses one monochromatic camera; as a result, the cameras alignment is not required, simplifying the 3D measurement system and reducing its cost. Three fringe patterns with different frequencies and three corresponding uniform gray-level patterns are set to different colors of red, green, and blue. Then Fourier transform profilometry (FTP) is employed to retrieve the 3D shape from the captured six images. While three uniform gray-level patterns can be used to eliminate the effects of the zero frequency term, they can be also used to generate the color texture of objects meanwhile. The proposed method only requires the capture of six monochromes, and the experimental results demonstrate the success of the proposed method.

Fabrication and demonstration of ultra-compact 3D measurement module using silica-based planar lightwave circuit

We fabricated an ultra-compact optical module using a silica-based planar lightwave circuit (PLC) for performing three-dimensional (3D) measurements. The module with a fiber, camera, lens, and flexible printed circuits is small enough to be attached to a tube with an inner diameter of 2.5 mm. The PLC is used as a fringe projector with a phase-modulation function and substrate for mounting the camera. A 3D measurement system based on a phase-shifting method was constructed using the module, and 3D profile measurements were performed on objects with thicknesses of 1.0, 2.0, and 3.0 mm. The experimental results indicated that the reconstructed shapes of the objects were clear enough for them to be recognized and the measurement variation was about 0.1 mm.

Interactive dense point clouds in a game engine

With the development of 3D measurement systems, dense colored point clouds are increasingly available. However, up to now, their use in interactive applications has been restricted by the lack of support for point clouds in game engines. In addition, many of the existing applications for point clouds lack the capacity for fluent user interaction and application development. In this paper, we present the development and architecture of a game engine extension facilitating the interactive visualization of dense point clouds. The extension allows the development of game engine applications where users edit and interact with point clouds. To demonstrate the capabilities of the developed extension, a virtual reality head-mounted display is used and the rendering performance is evaluated. The result shows that the developed tools are sufficient for supporting real-time 3D visualization and interaction. Several promising use cases can be envisioned, including both the use of point clouds as 3D assets in interactive applications and leveraging the game engine point clouds in geomatics.

Regional fuzzy binocular stereo matching algorithm based on global correlation coding for 3D measurement of rail surface

In view of the uncontrollable imaging quality of the electromagnetic railgun’s rail, based on the existing 3D measurement system, which combines binocular vision with active dot matrix illumination, a regional fuzzy binocular stereo matching algorithm based on global correlation coding is presented. Considering the lack of imaging details and textures and the problem of point target matching, the proposed stereo matching algorithm can get more complete and reliable matching results. Compared with the existing matching algorithms (such as SSD, SIFT, DP, BP, GC, etc.), the proposed matching algorithm can ensure the overall matching accuracy of left and right views, and has higher matching integrity. The implementation of the algorithm is that, the image spatial correlation of target image is firstly decoupled by coding, and then the L1 correlation constraint is calculated for the matched images. The combination of cyclic displacement matrix and random matrix is adopted here encoding the target image, which can make the coding result more robust. Meanwhile, the 3D measurement experiment of rail surface is done under dim light condition. The experimental results show that the matching integrity can reach 99.44 %. Through the experiment, the 3D depth map of the target scene is obtained.

Robust composite sine-trapezoidal phase-shifting algorithm for nonlinear intensity

Phase-shifting profilometry (PSP) is an efficient three-dimensional (3D) measurement technique. The accuracy of the PSP based 3D measurement system is generally affected by the nonlinear intensity response of the projector. In general, nonlinear errors can be reduced by projecting more fringe patterns, but this approach significantly increases the measuring time. To improve the measurement accuracy and speed, a new composite sine-trapezoidal phase-shifting profilometry technique that suppresses nonlinear error is proposed in this study. The main idea of the proposed method is projecting a set of sinusoidal fringe patterns and two sets of composite sine-trapezoidal fringe patterns with different intensity ranges in sequence. Among these patterns, the sinusoidal fringe is used to encode the pixel position, and the order of the wrapping phase is determined by the region code of the composite fringe. The flat intensity parts of the composite fringe are used to encode the nonlinear intensity response of the measurement system. Through system identification, the response parameters of the pixels can be obtained, and the gray value of the pixels can be corrected to gain a better phase distribution. Compared to the straight edges of the trapezoidal fringe, the sinusoidal edges of the composite fringe are more robust to the projector defocus, which improves the accuracy of the identification of the system intensity response model. Simulation results show that the proposed method can achieve a higher phase retrieval accuracy than the trapezoidal PSP and the sine PSP. The experiment results indicate that the proposed method has a better measurement accuracy than those of the standard 3-step and 4-step sine PSP methods.

A Real-Time 3D Measurement System for the Blast Furnace Burden Surface Using High-Temperature Industrial Endoscope.

Capturing the three-dimensional (3D) shape of the burden surface of a blast furnace (BF) in real-time with high accuracy is crucial for improving gas flow distribution, optimizing coke operation, and stabilizing BF operation. However, it is difficult to perform 3D shape measurement of the burden surface in real-time during the ironmaking process because of the high-temperature, high-dust, and lightless enclosed environment inside the BF. To solve this problem, a real-time 3D measurement system is developed in this study by combining an industrial endoscope with a virtual multi-head camera array 3D reconstruction method. First, images of the original burden surface are captured using a purpose-built industrial endoscope. Second, a novel micro-pixel luminance polarization method is proposed and applied to compensate for the heavy noise in the backlit images due to high dust levels and poor light in the enclosed environment. Third, to extract depth information, a multifeature-based depth key frame classifier is designed to filter out images with high levels of clarity and displacement. Finally, a 3D shape burden surface reconstruction method based on a virtual multi-head camera array is proposed for capturing the real-time 3D shape of the burden surface in an operational BF. The results of an industrial experiment illustrate that the proposed method can measure the 3D shape of the entire burden surface and provide reliable burden surface shape information for BF control.

FAst Detection Algorithm for 3D Keypoints (FADA-3K)

3D keypoint is widely used for object recognition and pose estimation with a 3D point cloud since it has robustness against measurement noise and occlusion. Many types of 3D keypoints and the corresponding detection methods of 3D keypoints have been proposed. It is essentially important to select suitable 3D keypoint depending on a target object, scene situation, and 3D measurement system. While there have been a lot of useful methods for detecting 3D keypoints, detecting time is an issue, especially for real-time applications, such as robot vision. The detecting of 3D keypoints tends to entail a trade-off between computation time and the robustness of the 3D keypoint. To solve these problems, we propose a FAst Detection Algorithm for 3D keypoints named FADA-3K. A user can select one of the suitable 3D keypoints and the corresponding detection method which has been already proposed since FADA-3K can be implemented as an add-on of the existing detection methods. Numerical experiments show that FADA-3K can achieve about nine times faster detection than conventional approaches to detecting 3D keypoints.

Calibration method of light field refocusing position in 3D dose measurement system based on scintillator

Calibration method of light field refocusing position in 3D dose measurement system based on scintillator

Development of 3D stress measurement system for surgical simulator

Development of 3D stress measurement system for surgical simulator

Bonding Performance of Fiber-Reinforced Polymer-to-Concrete Joints under the Effect of Corrosion Cracking

Externally bonded (EB) carbon fiber-reinforced polymers (CFRPs) have been progressively considered for application in concrete structures. However, the corrosion of reinforcing steel bars (rebars) in reinforced concrete (RC), which is more common in coastal environments than in inland environments, can degrade structural performance. The bonding performance of FRP-to-concrete joints can be further deteriorated by the degradation of the interfacial bonding behavior between the rebar (or rebars) and concrete cross-sectional area reduction at the steel bar plane induced by rust expansion. In this study, the effect of rebar corrosion on the FRP bonding performance of RC components was experimentally investigated for the first time. Single shear tests assisted by a 3D optical displacement measurement system were used to obtain the full-field distribution of specimen displacements. The test results show that, although the corrosion level and diameter of the steel bar slightly affected the bonding strength of FRP-to-concrete, the corrosion crack width increased as the steel bar corrosion level increased, which affected the failure mode. Hence, as the corrosion level of the steel bars increased, the likelihood of concrete cover separation increased. Finally, a modified strength design model accounting for the rebar corrosion level was proposed in this paper.

Surface and thickness measurement in the Targetlab of GSI

For characterization of targets and foils prepared at the target laboratory as well as for characterization of e.g. degrader or windows of internal customers, different analytical devices are available. Besides a lot of standard equipment, the target laboratory of GSI holds a 3D-measurement system (MicroProf®) equipped with optical sensors for measuring surface parameters as well as total thickness variations contact-free. In the paper the measuring principle including the possibilities and features of the MicroProf®-system are explained and some different applications are shown.