| 摘要 |
PURPOSE:To enable erasure of unnecessary information in the time required roughly for recording by disposing a means for generating an external magnetic field for erasure in accordance with a position where an erasing beam is irradiated and generating simultaneously a recording beam, erasing beam and tracking beam by separate generating means. CONSTITUTION:The direction of an external magnetic field 29 varies in the parts where light beam spots 21 and 22 are irradiated. The magnetic field 29 acts in an erasing direction in the part where the spot 21 is irradiated and in a recording direction in the part where the spot 22 is irradiated; at the same time rerecording of fresh information roughly simultaneously with erasing of the unnecessary information is made possible by using the spots 21, 22. The recording time is thus reduced without erasing the necessary region prior to recording as in the prior art. Since the min. required region is erased, such an accident of erasing erroneously the required information is prevented. |
