| 摘要 |
PURPOSE:To attain a bias magnetic field generating system having small power loss without using a mechanism which shifts coils by selecting optionally and electrically miniature coils set at plural positions and impressing a desired bias magnetic field at a desired area of a disk. CONSTITUTION:The light beam is irradiated on a disk 2 to form a spot from a pickup 7 containing the focusing and tracking functions for recording, etc. Then a bias magnetic field vertical to the disk surface is impressed to the area irradiated with said light beam to perform record or erasion of information. For this purpose, plural miniature coils 8 are arrayed on a substrate 9 on the surface opposite to the pickup 7 and centering on the disk 2. In this case, these coils 8 overlap properly with each other in the radius direction of the disk 2. A proper one of coils 8 is selected in response to the shift of the pickup 7, and a current is impressed to the selected coil 8. Thus a desired vertical bias field is generated. |
