| 摘要 |
PURPOSE:To prevent heat generation and power consumption from going to large by combining a permanent magnet and electromagnet effectively as an external magnetic field generating device. CONSTITUTION:As external magnetic field is entirely unnecessary at the time of reproduction 31, assuming that intensity of a magnetic field generated by a permanent magnet 26 as H1, current is let flow in an electromagnet to generate a magnetic field of reverse direction and the magnetic field of the permanent magnet 26 is canceled. Consequently, intensity 34 of the magnetic field on a disk becomes zero. A laser power 35 produces power g necessary for reproduction. At the time of an erasing/recording mode, current 33E is applied to a coil 30 to generate a magnetic field of the same direction with the direction of the magnetic field of the permanent magnet 26. Consequently, magnetic field caused by the permanent magnet 26 and magnetic field caused by the electromagnet are added and intensity 34 of the magnetic field on the disk becomes F(Oe). The laser power supplies power G necessary for recording and erasing respectively. |
