| 摘要 |
PURPOSE:To efficiently erase data by detecting data recorded in a medium and changing the intensity of beams corresponding to the signal. CONSTITUTION:A regeneration light source 3 emits regeneration beams of a semiconductor laser with relatively weak constant power, thereby to form a focus spot A onto a photochromic material 11 by an objective lens 2. The optical change of characteristics corresponding to the recording data is detected. The light projected from an erasure light source 4 forms a focus spot B on a recording layer of the medium 1 through a dichroic mirror 7 and the lens 2. The spot A is arranged precedent to the spot B on the same track. The time distance since a point, on the medium 1 passes A until the point reaches B agrees with the amount of time delay from a delay circuit 13. The intense erasure beam is cast only to a recording part on the medium 1, thereby ensuring efficient erasure and high reliability. |
