ABSTRACT For photometric stereo in capsule endoscopy, calibration of light source is crucial for improving the precision of surface normal estimation. Therefore, this paper presents an improved planar-mirror-based light source position calibration method: from captured images of light source and detected poses of planar mirror, light paths are retraced from camera to light source, and position of light source is triangulated with least square method. The contribution of this paper is that a refraction model of the planar mirror is employed in the retracement of light paths, thus the bias of light paths caused by refraction can be compensated and the position of light source can be estimated more precisely. The results of simulation and experiment show that the proposed method provides higher calibration accuracy than the current planar mirror-based calibration method and can improve the precision of subsequent photometric stereo-based 3D reconstruction. GRAPHICAL ABSTRACT

中文翻译：

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胶囊内窥镜光度立体光源位置标定方法

摘要 对于胶囊内窥镜中的光度立体，光源的校准对于提高表面法线估计的精度至关重要。因此，本文提出了一种改进的基于平面镜的光源位置标定方法：从捕获的光源图像和检测到的平面镜位姿，将光路从相机回溯到光源，并用最少的三角形对光源位置进行三角测量。方法。本文的贡献在于在光路回退中采用了平面镜的折射模型，从而可以补偿折射引起的光路偏差，更准确地估计光源的位置。仿真和实验结果表明，该方法比目前基于平面镜的标定方法提供了更高的标定精度，并且可以提高后续光度立体3D重建的精度。图形概要