  The reconstruction of particle trajectories makes it possible to distinguish
between different types of charged particles. In high-energy physics, where
trajectories are rather long, large size trackers must be used to achieve
sufficient position resolution. However, in low-background experiments tracks
are rather short and three dimensional trajectories could only be resolved in
time-projection chambers so far. For detectors of large volume and therefore
large drift distances, which are inevitable for low-background experiments,
this technique is limited by diffusion of charge carriers. In this work we
present a "proof-of-principle" experiment for a new method for the three
dimensional tracking of charged particles by scintillation light: We used a
setup consisting of a scintillator, mirrors, lenses and a novel imaging device
(the hybrid photo detector) in order to image two projections of electron
tracks through the scintillator. We took data at the T-24 beam-line at DESY
with relativistic electrons with a kinetic energy of 5 GeV and from this data
successfully reconstructed their three dimensional propagetion path in the
scintillator. With our setup we achieved a position resolution of about 28 mum
in the best case.
