| 摘要 |
PURPOSE:To attain proper recording or erasure depending on the radial position of a recording medium by controlling variably the strength of a magnetic field in response to the position in the 1st direction of the recording position of an optical head. CONSTITUTION:An optical head 17 is driven in radial direction of a recording medium 1 by an actuator 27 and moved to a desired write position. The radial position of the optical head 17 is detected by a head position detection section 61 via a scale 29, converted into a digital signal by an A-D converter 63 and fed to a CPU 25. The CPU 25 forms an electromagnetic coil driving control signal in response to radial position information of the optical head 17 detected by a head position detection section 61. A control signal is converted into an analog signal via a D-A converter 23 and fed to a current driver 22, which flows an exciting current to the coil 9 in response to the radial position of the optical head 17 according to the control signal. As a result, the strength of the magnetic field generated from the coil 9 changes according to the radial position of the optical head 17.
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