Yamaguchi Tetsuzo, Nakamoto Masahiko, Sato Yoshinobu, Konishi Kozo, Hashizume Makoto, Sugano Nobuhiko, Yoshikawa Hideki, Tamura Shinichi
Division of Interdisciplinary Image Analysis, Osaka University Graduate School of Medicine, Osaka, Japan.
Comput Aided Surg. 2004;9(5):203-14. doi: 10.3109/10929080500163505.
Oblique-viewing endoscopes (oblique scopes) are widely used in medical practice. They are essential for certain procedures such as laparoscopy, arthroscopy and sinus endoscopy. In an oblique scope the viewing directions are changeable by rotating the scope cylinder. Although a camera calibration method is necessary to apply augmented reality technologies to oblique endoscopic procedures, no method for oblique scope calibration has yet been developed. In the present paper, we formulate a camera model and a calibration procedure for oblique scopes. In the calibration procedure, Tsai's calibration is performed at zero rotation of the scope cylinder, then the variation of the external camera parameters corresponding to the rotation of the scope cylinder is modeled and estimated as a function of the rotation angle. Accurate estimation of the rotational axis is included in the procedure. The accuracy of this estimation was demonstrated to have a significant effect on overall calibration accuracy in the experimental evaluation, especially with large rotation angles. The projection error in the image plane was approximately two pixels. The proposed method was shown to be clinically applicable.
斜视内镜（斜镜）在医学实践中被广泛使用。它们对于某些手术至关重要，例如腹腔镜检查、关节镜检查和鼻窦内镜检查。在斜镜中，通过旋转镜筒可以改变观察方向。尽管将增强现实技术应用于斜视内镜手术需要一种相机校准方法，但尚未开发出用于斜镜校准的方法。在本文中，我们制定了一种用于斜镜的相机模型和校准程序。在校准程序中，在镜筒零旋转时执行蔡氏校准，然后将与镜筒旋转相对应的外部相机参数的变化建模并估计为旋转角度的函数。该程序包括对旋转轴的精确估计。在实验评估中，这种估计的准确性被证明对整体校准准确性有显著影响，尤其是在大旋转角度时。图像平面中的投影误差约为两个像素。所提出的方法被证明具有临床适用性。
