[en] Novel semi-transparent optical position sensors ('ALMY sensors') have been developed for the alignment monitoring systems of modern large-area tracking detectors. The high transmittance of up to 90% allows to align more than 10 sensors along a collimated laser beam. A position resolution of 1 μm and an uncertainty in the deflection of the traversing laser beam of less than 3 μrad have been achieved for sensitive areas of several square centimeters. For the thin-film amorphous silicon sensors, the required laser intensity could be minimised such that the performance is not deteriorated by aging effects. (orig.)