| 摘要 |
PURPOSE:To achieve a high density and to increase a storage capacity by differing the width or the depth of fine recessed and projecting parts formed by convergence light according to the multiple-value information to be recorded. CONSTITUTION:A light reflection region is formed on a recording medium or a concentric or spiral information track O1 is formed on a recording region and signal information is recorded along the track O1. The signal information on the track O1 is recorded by fine recessed and projecting shapes and the recessed and projecting shapes are formed by a first plane 61 and a second plane 62 whose heights are different each other and a boundary region between them. An amount of step d between the first and second planes 61 and 62 is uniform everywhere and the amount of step d is close to lambda/d if the wavelength of reproduction light in a substrate of the recording medium is set to lambda. On the other hand, a width W of the second plane 62 in a direction at right angle to the direction along the information track O1 changes depending on the location and information is given to a value W of the width and the position where the width changes. The amount of reduction in the quantity of light to be detected due to the interference of reflected light from the planes 61 and 62 and the timing of the change in quantity of light to be detected are detected trough signals. |
