Birkfellner Wolfgang, Figl Michael, Huber Klaus, Watzinger Franz, Wanschitz Felix, Hummel Johann, Hanel Rudolf, Greimel Wolfgang, Homolka Peter, Ewers Rolf, Bergmann Helmar
CARCAS-Group at the Kantonsspital Basel, Switzerland.
IEEE Trans Med Imaging. 2002 Aug;21(8):991-7. doi: 10.1109/TMI.2002.803099.
Computer-aided surgery (CAS), the intraoperative application of biomedical visualization techniques, appears to be one of the most promising fields of application for augmented reality (AR), the display of additional computer-generated graphics over a real-world scene. Typically a device such as a head-mounted display (HMD) is used for AR. However, considerable technical problems connected with AR have limited the intraoperative application of HMDs up to now. One of the difficulties in using HMDs is the requirement for a common optical focal plane for both the realworld scene and the computer-generated image, and acceptance of the HMD by the user in a surgical environment. In order to increase the clinical acceptance of AR, we have adapted the Varioscope (Life Optics, Vienna), a miniature, cost-effective head-mounted operating binocular, for AR. In this paper, we present the basic design of the modified HMD, and the method and results of an extensive laboratory study for photogrammetric calibration of the Varioscope's computer displays to a real-world scene. In a series of 16 calibrations with varying zoom factors and object distances, mean calibration error was found to be 1.24 +/- 0.38 pixels or 0.12 +/- 0.05 mm for a 640 x 480 display. Maximum error accounted for 3.33 +/- 1.04 pixels or 0.33 +/- 0.12 mm. The location of a position measurement probe of an optical tracking system was transformed to the display with an error of less than 1 mm in the real world in 56% of all cases. For the remaining cases, error was below 2 mm. We conclude that the accuracy achieved in our experiments is sufficient for a wide range of CAS applications.
计算机辅助手术（CAS），即生物医学可视化技术在手术中的应用，似乎是增强现实（AR）最具前景的应用领域之一。AR是指在真实场景上显示额外的计算机生成图形。通常使用头戴式显示器（HMD）等设备来实现AR。然而，到目前为止，与AR相关的诸多技术问题限制了HMD在手术中的应用。使用HMD的困难之一在于，真实场景和计算机生成图像需要共同的光学焦平面，以及用户在手术环境中对HMD的接受度。为了提高AR在临床上的接受度，我们对一款小型、经济高效的头戴式手术双目镜Varioscope（维也纳生命光学公司）进行了改造，使其适用于AR。在本文中，我们介绍了改良后的HMD的基本设计，以及将Varioscope的计算机显示器与真实场景进行摄影测量校准的广泛实验室研究的方法和结果。在一系列16次不同变焦系数和物距的校准中，对于640×480的显示器，平均校准误差为1.24±0.38像素或0.12±0.05毫米。最大误差为3.33±1.04像素或0.33±0.12毫米。在所有情况中，56%的情况下，光学跟踪系统的位置测量探头在现实世界中的位置转换到显示器上的误差小于1毫米。其余情况下，误差低于2毫米。我们得出结论，我们实验中所达到的精度足以满足广泛的CAS应用。
