Binocular Measurement System Research Articles

Accuracy evaluation for in-situ machining reference points binocular measurement based on credibility probability

Passive binocular measurement systems are being increasingly utilized in the in-situ industries of automobiles, aviation, and aerospace, etc. due to their excellent qualities of accuracy, efficiency, and cost performance. Whereas the barrier of evaluating the accuracy of measured objects resulted from the unequal equivalent focal length and quantization of pixels, has limited their further development and application of high requirements for in-situ machining, e.g., the measurement of machining reference points for the positioning of robotic drilling in aerospace manufacturing. In this paper, an accuracy evaluation method is proposed to address the problem. Firstly, the unequal equivalent focal length is considered to improve the accuracy of 3D reconstruction. Next, the credibility probability model is developed to calculate the probability of the observed error in the public view of the binocular measurement system and indicates the direction of improvement. Finally, the in-situ experiment is carried out to validate the method within the effective public view range of 300 mm × 300 mm. The experiment results show that the RMSs of observed errors are superior to 0.035 mm, and the credibility probabilities are all higher than 0.91; the maximum 3D reconstruction accuracy improvement is 60.3%, with the error reduced from 0.078 mm to 0.031 mm.

DETR-based binocular measurement system in road environment

DETR-based binocular measurement system in road environment

Research on Morphology Detection of Metal Additive Manufacturing Process Based on Fringe Projection and Binocular Vision

This paper considers the three-dimensional (3D) shape measurement of metal parts during an additive manufacturing process in a direct energy deposition (DED) printing system with high temperature and strong light; a binocular measurement system based on ultraviolet light source projection is built using fringe projection and Fourier analysis. Firstly, ultraviolet light projection and an optical filter are used to obtain high-quality fringe patterns in an environment with thermal radiation. Then, Fourier analysis is carried out by using a single deformed fringe, and a spatial phase unwrapping algorithm is applied to obtain an unambiguous unwrapping phase, which is used as the guiding basis for the binocular matching process and 3D shape reconstruction. Finally, the accuracy of the measuring system is evaluated using a standard ball-bar gauge and the measurement error of this system is within 0.05 mm @ 100 × 100 mm. The results show that the system can measure 3D shape changes of metal parts in the additive manufacturing process. The proposed method and system have the potential to be used for online inspection and quality control of additive manufacturing.

3D Reconstruction of Traditional Handicrafts Based on Binocular Vision

As an indispensable and essential material part of China's traditional culture, traditional handicrafts have played a more important role in modern life. It is not only the crystallization of the wisdom of the Chinese people of all nationalities but also an excellent platform to display China's long-standing culture. However, the protection and reconstruction of traditional handicrafts are relatively lagging. To realize the reconstruction of traditional handicrafts, this paper proposes an improved AD-Census stereo matching algorithm of a binocular measurement system for object positioning and three-dimensional reconstruction. Methods based on the principle of binocular vision measurement include firstly, histogram equalization, adaptive threshold Canny edge extraction, and expansion are used for image preprocessing; Secondly, the calibration method is used to complete camera calibration, remove camera distortion through stereo correction, and improve the AD-Census stereo matching algorithm based on gradient division of weak texture and edge area. Finally, the parallax map generated by the improved algorithm is used to realize three-dimensional reconstruction. The experimental results show that this method can control the error standard deviation within 0.5 mm, can realize the reconstruction of traditional handicrafts, have high accuracy, and can be widely used in practice.

Monocular gray code 3D shape measurement based on improved Siamese Network

As 3D information is widely used in more and more industries, simplification of 3D measurement operations and higher accuracy of measurement results are important development directions in the future. Compared with the binocular measurement system, simple equipment and convenient operation are the advantages of the monocular measurement; the disadvantage is that the measurement accuracy is low and it is greatly affected by the environment. This paper proposes a method that combines deep learning with traditional monocular Gray code 3D shape measurement technology. The space transformation network is used to improve the Siamese Network, and the single-view photos are taken through spatial transformation to obtain dual-view photos, and then matched through the Siamese Network. The purpose is to use monocular measurement equipment and methods to obtain the effect of binocular measurement. The deep learning network in this article has been pre-trained with a self-made data set before use. Compared with the original method, this method has higher accuracy in plane measurement, and has a significant improvement in depth measurement, successfully reducing the depth measurement error to less than 0.1mm.

An error reduction method of a binocular measurement system under vibrating conditions

To solve the problem of large measurement errors caused by vibrations of the surrounding environment, an error reduction method of a binocular measurement system is proposed. A light pen with a V-8 layout is designed to estimate the pose, and coded markers are used to establish a dynamic reference coordinate system to reduce the measurement error mainly caused by vibrations. The experimental results indicate that the light pen is highly accurate in pose estimation, and a root mean square error of the standard blocks and standard balls can be achieved within 0.02 mm when the measurement distance is 1.5 m. By measuring the straightness error of an ABB robot’s manipulator in a comparative experiment, the effective establishment of the dynamic reference coordinate system is preliminarily proven. The experiments are then conducted under vibrating conditions to calculate the standard deviations of the light pen probe center on the X-, Y-, and Z-axes with different quantities (3 and 4) of coded markers, which verify the high accuracy and real-time requirement of the method with a standard deviation below 0.040 mm and a processing speed above 45 frames per second when the measurement distance is 2 m.

3-D human pose measurement method based on deep learning and epipolar constraint

为了实现汽车座椅上三维人体姿态的高精度实时测量，基于现有二维人体关节点和三维人体关节点测量方法，提出了一种融合深度学习与外极线约束的三维人体姿态测量方法。该方法将二维人体关节点深度网络提取方法和双目测量系统相结合，采用双通道多阶段迭代网络分别提取左右相机图像中人体二维关节点，结合关节点位置的Brief特征和外极线约束，利用双目相机标定结果将匹配二维关节点信息转换到三维空间中，最终得到三维人体姿态。实验结果表明，文中提出方法在自采测试集中的检测精度可达到98%。通过得到三维关节点计算所得关键位姿角度的偏差小于10°。该文所提出的方法能够满足实际汽车座椅设计的数据采集要求。

Global Data Registration Technology Based on Dynamic Coded Points

Field measurement of large aviation components is important in many fields of study. In this paper, a global data registration method based on the dynamic coded points is proposed. The system used in this method contains the local and global control binocular measurement systems. The local binocular measurement system measures the data of each subdomain as the local measurement data by scanning. The dynamic coded points, which are encoded based on time parameter as their encoded values, are projected to the measured object’s surface using a projector. Two sets of systems acquire the dynamic coded points to calculate their encoded values and match them automatically. These systems calculate the transformation relations between the local coordinate system and the global control coordinate system, so the local measurement data coordinates are integrated into the global control coordinate system through the transformation relations, achieving the global data registration. Experimental results in the laboratory show that the process of matching of dynamic coded points is accurate and has high robustness, and the global registration method based on the coded points proposed by this paper can eliminate the accumulated error, reaching the precision of 0.0150%. Field experimental results show that the registration method proposed in this paper satisfies the measurement requirements of large-scale aviation components.

Pattern design and realization for calibrating near infrared camera in surgical navigation

A calibration board composed of 8 × 8 near-infrared surface-mounted diodes (NIR-SMDs) (940 nm) is designed. Meanwhile, a common binocular measurement system with the average error less than 0.1320 mm is used to obtain the geometric information of this board. A calibration method with the designed pattern is performed to obtain the parameters of the nearinfrared camera (NIRC). In the experiment, the average relative errors of focal length and principal point are 0.244% and 0.735%, respectively. The mean of image residuals is less than 0.01 pixel. The error of three-dimensional (3D) measurement is less than 0.3 mm. All those results indicate that the designed calibration board is suitable and accurate for calibrating NIRC.