| 摘要 |
PURPOSE:To improve position matching between a recording spot and a coil even if a very small coil is used by controlling the magnetic field generating coil so as to move as following the moving direction of a recording beam. CONSTITUTION:A photodetector 8 consists of two parts 8a, 8b, and when transmitted light is equally projected on both parts, i.e., when the position of an air core coil 3 united with the photodetector 8 by a coil supporting member 9 is exactly faced to the recording spot 7, because the detection signal levels of the both are equal, the output of a differential amplifier 11 is 0, and controlling action is not performed. If the recording spot 7 is dislocated in an arrow mark X-direction, the transmitted light 6b is dislocated in X-direction as well, and irradiated light to the photodetector 8 is increased, and the output level is increased by this portion, and the signal of the level proportional to this output difference is outputted from the differential amplifier 11, and a driving motor 12 is rotated, and a driving mechanism 13 is made to operate. Thus, in spite of the use of the very small air core coil 3, the recording spot and the position of the air core coil can be made to coincide exactly with each other. |
