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为测量系统的精确度,在工作距离500~1200 mm范围内,对半径为20.01 mm的标准球进行扫描重建。在视场内选取12个不同位置,分别计算出不加折射校正算法和加折射校正算法后标准球的测量半径。用R表示未加折射校正算法时水下的测量半径,表示加折射校正后的测量半径。经计算可得标准球半径,条纹提取结果如图11所示。实际测量的标准球半径如表1所示。
Figure 11. (a) Error experiment of underwater standard ball; (b) Fringe center extraction result of underwater standard
在视场内选取12个不同位置,用半径为20.01 mm的标准球作为被测物体进行测量,完成水下测量实验,通过计算可得标准球的测量半径R,详细测量结果如表1所示。
Distance/mm R/mm Error/mm ${R_c}$/mm ${\rm Error}{_c}$/mm 500 21.84 1.83 20.12 0.11 550 21.86 1.85 20.09 0.08 600 21.64 1.63 20.20 0.19 650 21.69 1.68 20.23 0.22 700 21.78 1.77 20.30 0.29 750 21.81 1.80 19.74 0.27 800 21.88 1.87 20.35 0.34 850 21.89 1.88 19.65 0.36 900 21.86 1.85 20.47 0.46 950 22.07 2.06 20.50 0.49 1000 21.98 1.97 20.58 0.57 1200 22.12 2.11 19.41 0.6 Average 21.87 1.86 20.14 0.13 Max 22.12 2.11 20.58 0.60 Table 1. Measurement result and error of standard ball
由表1可知,未加折射校正时,标准球的测量误差在2.2 mm范围内,最大测量误差为2.11 mm。加入折射校正后,重建的标准球半径误差范围在0.6 mm内。由此可知:加入了折射校正算法后,系统的重建精度得到了显著提高,证明文中提出的水密装置折射校正算法具有较好的准确性和有效性。
Research on the 3D laser reconstruction method of underwater targets
doi: 10.3788/IRLA20210693
- Received Date: 2021-09-18
- Rev Recd Date: 2021-12-09
- Available Online: 2022-08-31
- Publish Date: 2022-08-31
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Key words:
- underwater three-dimensional imaging /
- linear laser scanning /
- fringe center extraction /
- three-dimensional reconstruction /
- Delaunay triangulation
Abstract: A three-dimensional reconstruction system for underwater lasers is proposed, which is composed of a camera, green linear laser and turntable. The three-dimensional reconstruction of the target area is realized by analyzing and processing the image scanned by the system. In the aspect of point cloud processing, this paper combines the alpha shape boundary extraction algorithm and Delaunay triangulation to realize the filtering and reconstruction of point clouds. Aiming at the problem of viewing angle error caused by light refraction on different media surfaces in the experiment, a refraction correction algorithm is proposed, and the error experiment is carried out with a standard ball of known size. The results show that at a working distance of 500-1200 mm, the system can restore the three-dimensional morphology of underwater target objects and regions, and the reconstruction error is less than 0.6 mm, which meets the design requirements and provides a new reference for underwater three-dimensional reconstruction technology.