A semiconductor structure having a textured nitride-based layer. The system includes delivery apparatus remotely located from the care provider, wherein the apparatus stores a plurality of sealed unit dose packages that are delivered to a patient at a scheduled dosing time. The illumination system is configured so that light components in point-symmetrical relationship with each other, which are produced during use of the illumination system and which are only superposed in the object plane, have mutually orthogonal polarization states. In this manner, the timing signal has an expected quality level equal to or greater than the quality level of the reference clock signal.