Event-Based Method for High-Speed 3D Deformation Measurement under Extreme Illumination Conditions
Authors: Banglei Guan, Yifei Bian, Zibin Liu, Haoyang Li, Xuanyu Bai, Taihang Lei, Bin Li, Yang Shang, Qifeng Yu
Organizations: College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China. · Hunan Provincial Key Laboratory of Image Measurement and Vision Navigation, Changsha 410073, China.
Background: Large engineering structures, such as space launch towers and suspension bridges, are subjected to extreme forces that cause high-speed 3D deformation and compromise safety. These structures typically operate under extreme illumination conditions. Traditional cameras often struggle to handle strong light intensity, leading to overexposure due to their limited dynamic range. Objective: Event cameras have emerged as a compelling alternative to traditional cameras in high dynamic range and low-latency applications. This paper presents an integrated method, from calibration to measurement, using a multi-event camera array for high-speed 3D deformation monitoring of structures in extreme illumination conditions. Methods: Firstly, the proposed method combines the characteristics of the asynchronous event stream and temporal correlation analysis to extract the corresponding marker center point. Subsequently, the method achieves rapid calibration by solving the Kruppa equations in conjunction with a parameter optimization framework. Finally, by employing a unified coordinate transformation and linear intersection, the method enables the measurement of 3D deformation of the target structure. Results: Experiments confirmed that the relative measurement error is below 0.08%. Field experiments under extreme illumination conditions, including self-calibration of a multi-event camera array and 3D deformation measurement, verified the performance of the proposed method. Conclusions: This paper addressed the critical limitation of traditional cameras in measuring high-speed 3D deformations under extreme illumination conditions. The experimental results demonstrate that, compared to other methods, the proposed method can accurately measure 3D deformations of structures under harsh lighting conditions, and the relative error of the measured deformation is less than 0.1%.
Figures & tables
Figure 1: Flow diagram of the event-based measurement method for high-speed 3D deformation under extreme illumination conditions.
Figure 2: Corresponding points extraction from event streams generated by various event cameras.
Input
Corresponding points for each camera P , Iteration count i , Initial value of camera projection matrix M
Output
Intrinsic parameters K , extrinsic parameters R,T
1
Calculate scale factor
2
Optimize the projection structure using the bundle adjustment method
3
Decompose the measurement matrix to obtain the projection reconstruction of the camera matrix and structure matrix
4
Perform Euclidean reconstruction to obtain camera parameters
5
By calculating the reprojection errors of polar geometry and dynamic landmark points, outlier projection points are eliminated
Table 1: Calibration algorithm.
Figure 3: Reference coordinate system transformation.
Figure 4: Experimental configuration.
Extrinsics
Event camera 1
Event camera 2
Event camera 3
(fx,fy)
(1778.5077, 1772.3397)
(1756.2173, 1757.6988)
(1816.1340, 1809.6153)
(Cx,Cy)
(639.5, 359.5)
(639.5, 359.5)
(639.5, 359.5)
(k1,k2)
(-0.05359, 0.33899)
(-0.09119, 0.38824)
(-0.11437, 0.91938)
(p1,p2)
(-0.00157, -0.00479)
(0.00149, -0.00318)
(-0.00144, 0.00497)
Table 2: Calibration results of each camera intrinsics.
Event-driven Perception for Robotics, Istituto Italiano di Tecnologia, Italy · Humanoid Sensing and Perception, Istituto Italiano di Tecnologia, Italy · University of Genoa, Genoa, Italy