Abstract
Laser triangulation sensors (LTS) are widely used to acquire depth information in industrial applications. However, the parameters of the components, e.g., the camera, of the off-the-shelf LTS are typically unknown. This makes it difficult to recalibrate the degenerated LTS devices during regular maintenance operations. In this paper, a novel one-dimensional target-based camera intrinsic matrix-free LTS calibration method is proposed. In contrast to conventional methods that calibrate the LTS based on the precise camera intrinsic matrix, we formulate the LTS calibration as an optimization problem taking all parameters of the LTS into account, simultaneously. In this way, many pairs of the camera intrinsic matrix and the equation of the laser plane can be solved and different pairs of parameters are equivalent for displacement measurement. A closed-form solution of the position of the one-dimensional target is proposed to make the parameters of the LTS optimizable. The results of simulations and experiments show that the proposed method can calibrate the LTS without knowing the camera intrinsic matrix. In addition, the proposed approach significantly improves the displacement measurement precision of the LTS after calibration. In conclusion, the proposed method proved that the precise camera intrinsic matrix is not the necessary condition for LTS displacement measurement.
Highlights
The laser triangulation sensor (LTS) is widely used to acquire depth information in industrial applications such as rail inspection [1], reverse engineering [2], and workpiece inspection [3]
The LTS calibration methods can be categorized as pattern-based methods, target geometry-based methods, and auxiliary device-facilitated methods according to their different calibration principles
The results show that the proposed approach significantly improves displacement measurement precision of the LTS after calibration
Summary
The laser triangulation sensor (LTS) is widely used to acquire depth information in industrial applications such as rail inspection [1], reverse engineering [2], and workpiece inspection [3]. Some camera intrinsic matrix-free methods are proposed [16,17,18,19,20], the auxiliary devices such as 3D chessboard boxes [16,17,18,19] and guide rails [20] that have to be fixed on the ground are used in the calibration process. In contrast to the traditional methods that rely on the precise camera intrinsic matrix [1,2,4,5,6,7,8,9,10,11,12,13,14,15] or methods that use auxiliary devices [16,17,18,19,20], we formulate the LTS calibration as an optimization problem without the need for either of them. After presenting the proposed method the results of several simulation and real-world experiments will be presented to verify the efficacy of the proposed method
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