A light source includes a light emitting semiconductor device. When data B is to be recorded in the region A beyond multiplex-recording number M, the recording control section multiplex-records page data B in the buffer region of the region A within the range of the maximum multiplex-recordable number N. The encoded entities each have a one-to-one mapping to their corresponding one of the entities in the temporal order. Instead, such an additional tilt position requires that there at least be a tilt component in a direction orthogonal to the tilt axis.