| 摘要 |
PURPOSE:To improve the stability in case of recording, reproduction and erasion by constituting a magnetic circuit by making the interval of a magnetic pole and a recording medium surface different in the diameter direction of a recording medium, so that the strength of an applied magnetic field goes to different between the innermost peripheral track and the outermost peripheral track of the medium, and also constituting it so that its polarity can be inverted in accordance with the time when information is recorded and the time when it is erased. CONSTITUTION:A magnetic field applying use magnetic circuit 12 is provided so that an interval (h) between a magnetic pole and a disk surface becomes different. Therefore, the applied bias magnetic field strength is corrected property in advance between the inside peripheral part track and the outside peripheral part track. Accordingly, in a state that the laser output remains constant and also the strength of a magnetic field of a magnetic circuit itself remains constant, a size of a recording pit can be made constant and recorded in both the inside and the outside peripheral parts of the disk. Also, by inverting the polarity of the magnetic circuit by a rotary solenoid 13, and executing an erasion of recorded information, the laser output can be erased in the almost same state as the time of recording.
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