  We describe and show results of a photographic technique for continuously
monitoring the position, orientation, and shape of a thin-film muon stopping
target for the MEG II experiment. The measurement is complicated by the target
being located in a region with 1.3 T magnetic field, significant radiation and
having limited access. The technique achieves a measurement precision of 0.010
mm normal to and 0.030 mm parallel to the film surface, significantly better
than required for the MEG II experiment.

Instrumentation and Detectors