1. Field of the Invention
The present invention relates to a magnetic head drive device for driving a magnetic head by supplying a drive current thereto so as to record an information signal on a magneto-optical recording medium, and a magneto-optical recording apparatus using the same.
2. Related Background Art
Conventionally, as a magneto-optical recording apparatus for recording an information signal on a magneto-optical recording medium such as a magnetooptical disk or the like at high density, an apparatus using a magnetic field modulation scheme is known. A magnetic field modulation magneto-optical recording apparatus comprises an optical head, a magnetic head, a magnetic head drive device, and drive means for driving a magneto-optical recording medium. When an information signal is recorded on a magneto-optical recording medium using such a magneto-optical recording apparatus, the optical head irradiates a high-power laser beam focused to a small beam spot onto a magnetic layer of the magneto-optical recording medium while driving the magneto-optical recording medium relative to the optical head and magnetic head. At the same time, the magnetic head drive device supplies a current modulated by the information signal to the magnetic head, so that the magnetic head perpendicularly applies a magnetic field modulated according to the information signal to the portion irradiated with the laser beam of the magneto-optical recording medium. As a result, a magnetic domain, the direction of magnetization of which changes in correspondence with the direction of magnetic field applied, is formed in the magnetic layer, thus recording the information signal. Using such a magnetic field modulation scheme, an information signal can be recorded at a very high density.
When the information signal recorded in this way is to be reproduced, the magneto-optical recording medium is driven, and at the same time, the optical head irradiates a lower-power laser beam than that upon recording, which is focused to a small beam spot, onto the magnetic layer of the magneto-optical recording medium. In this case, since the plane of polarization of the laser beam reflected by the magnetic layer rotates in correspondence with the direction of magnetization of the magnetic domain, it is detected by a photosensor provided to the optical head, and the information signal is reproduced based on the detection signal.
Superresolution reproduction is conventionally known. This technique uses a magneto-optical recording medium, a magnetic layer of which is comprised of a plurality of layers including at least a recording layer and reproduction layer, and transfers magnetization formed in the recording layer to the reproduction layer. Up on reproduction of an information signal, a laser beam is irradiated onto the magnetic layer, and at the same time, a magnetic field applying means applies a given magnetic field, so that the magnetization in a local region of the reproduction layer, which has reached high temperature upon irradiation of the laser beam, is switched in the direction of the applied magnetic field, irrespective of the magnetization formed in the recording layer, thus detecting a magnetic domain smaller than the beam spot size.
Especially, Japanese Patent Laid-Open Application No. 3-242845 has proposed a recording/reproduction scheme in which an information signal is recorded by magnetic field modulation, and the recorded information signal is reproduced by superresolution reproduction. With this scheme, an information signal can be recorded at a very high density, and the recorded information signal can be reproduced with high resolution.
However, conventionally, inorder to attain superresolution reproduction, a means for applying a given magnetic field is required in addition to a magnetic field applying means for magnetic field modulation recording, even though superresolution reproduction is possible to attain. For this reason, magnetic heads for magnetic field modulation and superresolution reproduction, and their drive devices must be independently equipped, and an expensive apparatus with a complicated arrangement is required.