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Non-central refractive camera calibration using co-planarity constraints for a photogrammetric system with an optical sphere cover
Optics and Lasers in Engineering ( IF 3.5 ) Pub Date : 2021-04-01 , DOI: 10.1016/j.optlaseng.2020.106487
Wenjuan Yang , Xuhui Zhang , Hongwei Ma , Guangming Zhang , Gang Yang

Abstract Optical sphere covers are widely used in photogrammetric systems to protect camera systems from external conditions. The spherical refraction can cause severe non-linear distortion, resulting in imprecise and unreliable measurements. In particular the cameras with a relatively thick optical sphere cover (e.g. underground or underwater cameras). However, the conventional perspective camera model are not suitable for such spherical refraction calibration problem. This study presents a novel non-central refractive calibration technique for cameras with an optical sphere cover. Considering the general situation in which the camera optical axis could not pass through the spherical center, a universal spherical refraction geometric model was established with coplanarity constraints. The model introduces modified perspective center and enables the spherical refraction can be integrated into the equivalent collinearity equations, which make it possible to describe explicitly the correspondences between the image points and object coordinates. Moreover, a calibration technique is proposed to estimate relative orientation parameters. With no need to gain explicit knowledge of object space coordinates, the spherical refraction calibration can be performed with known refractive index as well as the radius of sphere cover. Numerical and experimental results demonstrated the proposed spherical refraction calibration model to be both effective and robust, which can achieve high levels of calibration accuracy.

中文翻译:

使用共面约束的非中心折射相机标定用于具有光学球盖的摄影测量系统

摘要 光学球罩广泛用于摄影测量系统,以保护相机系统免受外部条件的影响。球面折射会导致严重的非线性失真,导致测量不精确和不可靠。特别是具有相对较厚的光学球面罩的摄像机(例如地下或水下摄像机)。然而,传统的透视相机模型不适合这种球面折射标定问题。本研究提出了一种用于具有光学球面罩的相机的新型非中心折射校准技术。针对相机光轴无法通过球心的普遍情况,建立了具有共面性约束的万能球面折射几何模型。该模型引入了修正的透视中心,使球面折射可以整合到等效共线性方程中,从而可以明确地描述像点和物体坐标之间的对应关系。此外,提出了一种校准技术来估计相对方向参数。无需获得物体空间坐标的明确知识,球面折射校准可以在已知折射率和球面覆盖半径的情况下进行。数值和实验结果表明,所提出的球面折射校准模型既有效又稳健,可以实现高水平的校准精度。这使得可以明确描述图像点和对象坐标之间的对应关系。此外,提出了一种校准技术来估计相对方向参数。无需获得物体空间坐标的明确知识,可以使用已知的折射率和球体覆盖半径进行球面折射校准。数值和实验结果表明,所提出的球面折射校准模型既有效又稳健,可以实现高水平的校准精度。这使得可以明确描述图像点和对象坐标之间的对应关系。此外,提出了一种校准技术来估计相对方向参数。无需获得物体空间坐标的明确知识,球面折射校准可以在已知折射率和球面覆盖半径的情况下进行。数值和实验结果表明,所提出的球面折射校准模型既有效又稳健,可以实现高水平的校准精度。球面折射校准可以在已知的折射率以及球体覆盖半径的情况下进行。数值和实验结果表明,所提出的球面折射校准模型既有效又稳健,可以实现高水平的校准精度。球面折射校准可以在已知的折射率和球面覆盖半径的情况下进行。数值和实验结果表明,所提出的球面折射校准模型既有效又稳健,可以实现高水平的校准精度。
更新日期:2021-04-01
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