An optical device provides optical routing functions, such as switching or redirecting of optical signals. When recording moving picture data on a rewritable recording medium, seamless presentation information, a part of navigation data, is recorded along with the picture data for seamless presentation of the recorded picture data. A magnetic induction sensor system adapted for magnetic induction inspection of at least one rail of the track is attached to the detector carriage. A blade for cutting various materials is attached to the closed of the inner sleeve.