Monocular Vision Measurement System Research Articles

A dual-projector three-dimensional measurement model for shading problem of micro-scale object complex surface

Considering the inherent defects of the traditional triangulation method, always a shadow area is produced in the image collected by the camera. In this work, based on the traditional monocular vision measurement system, an auxiliary light source was added to alleviate the shadow problem. Two symmetrical digital light processing (DLP) projectors were also employed to project the modulated monochrome red fringe patterns and the monochrome blue fringe patterns onto the object, whereas the distorted fringe patterns were captured by the colour camera. The image collected by the colour camera was separated, whereas the deformation fringe information of the measured object was obtained in the red channel and blue channel, respectively. Fusion of red and blue channels information to eliminate measurement shadows. From the experimental results, the root mean square error (RMSE) of the system was about 6µm, and this method can effectively solve the shadow problem in small object measurement.

A Monocular Vision Relative Displacement Measurement Method Based on Bundle Adjustment Optimization and Quadratic Function Correction

In order to meet the requirements of high-precision target displacement measurement, this paper proposed a measurement method based on monocular vision measurement system by which the advantages of simple structure, convenient debugging, easy to install and calibrate is recognized. This method first uses the bundle adjustment algorithm with conditional constraints to optimize the solution results of the orthogonal iterative algorithm, then calculates the relative poses of the optimization results, finally establishes an error correction model to perform secondary optimization on the relative poses. The experimental results show that the method proposed in this paper can reduce more than 54% average error of displacement measurement results, and the error between the final displacement measurement results and the actual displacement values is controlled at 0.4mm level, which proves that the method has good practical value.

Infrared LEDs-Based Pose Estimation With Underground Camera Model for Boom-Type Roadheader in Coal Mining

Accurate and reliable pose estimation of a boom-type roadheader is of great importance in order to maintain the efficiency of automatic coal mining. The stability and accuracy of conventional measurement methods are difficult to be guaranteed on account of vibration noise, magnetic disturbance, electrostatic interference, and other factors in an underground environment. In this paper, a vision-based non-contact measurement method for cutting-head pose estimation is presented, which deploy a 16-point infrared LED target on the boom-type roadheader to tackle the low-illumination, high-dust, and complicated background. By establishing a monocular vision measurement system, the cutting-head pose is estimated through processing the LED target images obtained from an explosion-proof industrial camera mounted on the roadheader. After analyzing the measurement mechanism, an underground camera model based on the equivalent focal length is built to eliminate refraction errors caused by the two-layer glasses for explosion-proof and dust removal. Then, the pose estimation processes, including infrared LEDs feature point extraction, spot center location, and an improved P4P method based on dual quaternions, are carried out. The influence factors of cutting-head pose estimation accuracy are further studied by modeling, and the error distribution of the main parameters is investigated and evaluated. The numerical simulation and experimental evaluation are designed to verify the performance of the proposed method. The results show that the pose estimation error is in line with the numerical prediction, achieving the requirements of cutting-head pose estimation in underground roadway construction in the coal mine.

A Monocular Vision Measurement System of Three-Degree-of-Freedom Air-Bearing Test-Bed Based on FCCSP

A monocular vision-based pose measurement system is provided for real-time measurement of a three-degree-of-freedom (3-DOF) air-bearing test-bed. Firstly, a circular plane cooperative target is designed. An image of a target fixed on the test-bed is then acquired. Blob analysis-based image processing is used to detect the object circles on the target. A fast algorithm (FCCSP) based on pixel statistics is proposed to extract the centers of object circles. Finally, pose measurements can be obtained when combined with the centers and the coordinate transformation relation. Experiments show that the proposed method is fast, accurate, and robust enough to satisfy the requirement of the pose measurement.

熔覆层检测中单目视觉测量系统的简易标定

熔覆层检测中单目视觉测量系统的简易标定

A monocular vision system for online pose measurement of a 3RRR planar parallel manipulator

In this paper, we develop a monocular vision system for online pose measurement of a 3-RRR planar parallel manipulator (PPM). By combining with a camera with global shutter, an active marker array, an industrial personal computer, and a degenerated perspective-n-points (DPnP) algorithm, a monocular vision measurement system (MVMS) is established. To improve measuring accuracy of the MVMS, factors that cause inaccuracy including the lens distortion, non-perpendicular angle, and input parameters’ uncertainty are analyzed and modeled in detail. In the simulation, effects of these error factors on the accuracy of the MVMS are quantitatively displayed, and comparisons between the DPnP algorithms and other state-of-art PnP algorithms are conducted. Experimental tests on the constructed MVMS demonstrate that it not only can accurately and efficiently measure pose of the 3RRR PPM, but possesses a higher operability and stability compared to the laser tracker.

A monocular vision system based on cooperative targets detection for aircraft pose measurement

In this paper, a monocular vision measurement system based on cooperative targets detection is proposed, which can capture the three-dimensional information of objects by recognizing the checkerboard target and calculating of the feature points. The aircraft pose measurement is an important problem for aircraft’s monitoring and control. Monocular vision system has a good performance in the range of meter. This paper proposes an algorithm based on coplanar rectangular feature to determine the unique solution of distance and angle. A continuous frame detection method is presented to solve the problem of corners’ transition caused by symmetry of the targets. Besides, a displacement table test system based on three-dimensional precision and measurement system human-computer interaction software has been built. Experiment result shows that it has a precision of 2mm in the range of 300mm to 1000mm, which can meet the requirement of the position measurement in the aircraft cabin.

空间协同位姿单目视觉测量系统设计与实验

空间协同位姿单目视觉测量系统设计与实验

Portable monocular light pen vision measurement system.

This paper introduces a portable monocular vision measurement system that is suitable for measuring complex object surfaces or hidden features. The system mainly consists of a light pen, a camera, and a portable computer. First, without any control point, a camera calibration method based on the bundle adjustment is developed. This method can also be applied to calculate the positions of the feature points on the light pen. Second, we calibrate the probe tip center, since the position of the replaceable stylus is uncertain. Last, by taking images of the light pen when the stylus contacts the object's surface, we get the measured point's position. This measuring system is portable, efficient, and high-precision. Experiments show that in a 100 mm×200 mm field, the position errors of 66 points are less than 30μm.

A Monocular Vision Measurement Algorithm Based on the Underwater Robot

A monocular vision measurement system was proposed based on the underwater robot, which used a single camera as visual sensor and used inertial navigation system to measure position and attitude. In this paper, the processing of underwater target images and the parameter calibration algorithm for visual measurement system were discussed, and then the visual measurement mathematic model of underwater robot was derived using the pose information of the inertial navigation system. Vision measuring principle validation tests for underwater robot have been carried out to detect underwater targets. The experiments verify that the monocular vision measurement algorithm proposed for underwater robot is effective with a preferably accuracy.

光笔式单目视觉测量系统的关键技术

In order to achieve the high-precision,large-size,three-dimensional space and real-time measurement of mechanical components,a monocular vision measurement system with a light pen was established. The new technology,algorithm converting model,the optimization of camera focal length and the position calibration of the light pen probe were studied. First,a new type of light pen which was designed by using the photolithography process was proposed. Then,based on resection principle of single image space in the close-range photogrammetry,the new conversion relationship between the light pen coordinate system and the camera coordinate system was established. Optimal exterior orientation elements of single image space was solved by least squares adjustment method in the loop iteration,and basic parameters of the transformation model were determined. Finally,the impacts of focal length on the result of monocular vision measurement system were analyzed,and a method to determine the relatively accurate focus length and the position of light pen probe in the coordinate system of the light pen was proposed. Experimental results indicate that the stability errors in the xaxis,y-axis,z-axis directions of the camera coordinate system are 0. 042 733 mm,0. 048 513 mm and0. 066 39 mm,respectively,and the maximum measuring error is 0. 173 mm. These results meet the requirements of monocular vision measurement system with a light pen for stability and high accuracy.