Accuracy analysis for triangulation and tracking based on time-multiplexed structured light

Type of publication:  Artikel
Zeitschrift: Medical Physics
Band: 41
Nummer: 8
Jahr: 2014
Monat: August
Seiten: 082701
Notiz: High-Accuracy Head Tracking
DOI: 10.1118/1.4890093
Abriss: Purpose: Our research group is currently developing a new optical head tracking system for in10 tracranial radiosurgery. This tracking system utilises infrared laser light to measure features of the soft tissue on the patient’s forehead. These features are intended to offer highly accurate registration with respect to the rigid skull structure by means of compensating for the soft tissue. In this context, the system also has to be able to quickly generate accurate reconstructions of the skin surface. For this purpose, we have developed a laser scanning device which uses time-multiplexed 15 structured light to triangulate surface points. Methods: The accuracy of our laser scanning device is analysed and compared for different triangulation methods. These methods are given by the Linear-Eigen method and a non-linear least squares method. Since Microsoft’s Kinect camera represents an alternative for fast surface reconstruction, our results are also compared to the triangulation accuracy of the Kinect device. Moreover, our laser 20 scanning device was used for tracking of a rigid object to determine how this process is influenced by the remaining triangulation errors. For this experiment, the scanning device was mounted to the end-effector of a robot to be able to calculate a ground truth for the tracking. Results: The analysis of the triangulation accuracy of our laser scanning device revealed an RMS error of 0.16 mm. In comparison, the analysis of the triangulation accuracy of the Kinect device 25 revealed an RMS error of 0.89 mm. It turned out that the remaining triangulation errors only cause small inaccuracies for the tracking of a rigid object. Here, the tracking accuracy was given by a RMS translational error of 0.33 mm and a RMS rotational error of 0.12 degrees. Conclusion: This paper shows that time-multiplexed structured light can be used to generate highly accurate reconstructions of surfaces. Furthermore, the reconstructed point sets can be used 30 for high-accuracy tracking of objects, meeting the strict requirements of intracranial radiosurgery.
Autoren: Wagner, Benjamin
Stüber, Patrick
Wissel, Tobias
Bruder, Ralf
Schweikard, Achim
Ernst, Floris