DaSchlegel

Chair for Computer Aided Medical Procedures & Augmented Reality
Lehrstuhl für Informatikanwendungen in der Medizin & Augmented Reality

Predicting the Accuracy of Optical Tracking Systems

Student Project (Diplomarbeit)

There exist several optical tracking systems on the market that use infrared reflective balls as markert targets for six degree of freedom tracking. Examples are the dtrack system by A.R.T. and the optotrack or polaris system by Northern Digital. However, there is no possibility to estimate the quality of a specific marker configuration in advance only from the geometric layout of the marker balls.

The goal of this project is to build a geometrical accuracy and reliability model for such marker configurations and then evaluate the model by empirical measurements.

Error Covariances for Optical Marker Targets

Head Target, from A.R.T. homepage at www.ar-tracking.dehmd_pos.jpg hmd_rot.jpg

Error Covariances for a stereo camera system

This movie shows the calculated covariance ellipsoids in the xz plane for a testsetup. The covariances in the imageplane are supposed to 0.1 [mm] in both direction. The baseline of the two cameras is 10[mm] and the focal length is set to 1[mm]. The magnification of the covariance ellipses is set to factor 0.01.

cameras.jpg

The following screenshots show the accuracy tracking a single feature for a test setup with a 2-ocular and a 3-ocular optical tracking system. The colors visualize the estimated rms error.

Error Prediction for a monocular camera system

Monocular tracking systems are operating with only one sensor. Due to the lack of the second camera it is not possible to track a single spatial point because no triangulation is possible. By combining more than one feature point rigidly to a marker target the pose of the marker target can be determined if the model of the tracked target is known.

3D plots showing qualitative uncertainties with respect to two angles at a fixed distance. The left plot is visualizing the rms error of estimating the distance to the target and the right plot shows the rms error of estimating the orientation.

Documents


ProjectForm
Title: Predicting the Accuracy of Optical Tracking Systems
Abstract: There exist several optical tracking systems on the market that use infrared reflective balls as markert targets for six degree of freedom tracking. Examples are the dtrack system by A.R.T. and the optotrack or polaris system by Northern Digital. However, there is no possibility to estimate the quality of a specific marker configuration in advance only from the geometric layout of the marker balls.The goal of this project is to build a geometrical accuracy and reliability model for such marker configurations and then evaluate the model by empirical measurements.
Student: Michael Schlegel
Director: Gudrun Klinker
Supervisor: Martin Bauer
Type: Diploma Thesis
Status: finished
Start: 2005/12/15
Finish: 2006/07/15


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