| 摘要 |
PURPOSE:To set a tracking line without decreasing the area of a data storage area by providing a recessed part and a projecting part alternately in parallel to a data recording face of an optical recording medium and selecting a step between the recessed part and the projecting part shallower than the depth of focus of the optical system used for data write/read. CONSTITUTION:The optical recording medium is constituted by providing the recessed part 3a and the projecting part 3b alternately in parallel as a data storage area to the storage area 2 provided to the major face of a card type base 1. The recessed part 3a and the projecting part 3b are constituted by providing a step smaller than the depth of focus of the optical system in use, e.g., nearly 1mum to the upper face of the storage area 2. Since the recessed part 3a and the projecting part 3b have the step, when a light beam is radiated to the boundary E, the brightness of the reflected light of the projecting part closer to the light source is high and that of the recessed part is low. In this case, since the step is selected to be smaller than the depth of focus of the optical system used for read/write, the brightness distribution of the reflected light is unchanged even if focusing is applied to the light beam for read/write. |
