| 摘要 |
PURPOSE:To reduce the size of a driving circuit by moving a magnetic field producing means so that the irradiation position of a light beam is within its magnetic field range, thus limiting the magnetic field production range and reducing the size and weight of the producing means, and reducing generated heat at the time of the use of an electromagnet. CONSTITUTION:A pit is formed or erased on an irradiated part in an effective magnetic field area with a bias magnetic field or erasing magnetic field produced by the electromagnet 7. An optical head 3 moves according to a track and when the irradiation position of the light beam is in the effective magnetic field area, the electromagnet 7 does not move, but when the irradiation position moves toward an end of the effective area, a control circuit 5 outputs a control signal to a driver 10 to drive a stepping motor 9, which moves the electromagnet 7 to make the magnetic field in the effective magnetic field area operate on the irradiation position. Consequently, the magnetic field producing means is reduced in size and weight to reduce the generated heat at the time of the use of the electromagnet, thereby reducing the size of the driving circuit. |
