| 摘要 |
PURPOSE:To easily and surely rewrite only a part of a disc by moving an optical system accurately to specify the irradiated position of a laser light. CONSTITUTION:An erasing head 2, a recording and reproducing head 8, objective lens actuators 4 and 10, and bias coils 14 and 15 are fixed to a base, which can be moved in the radial direction of the disc, as a head block. Means (actuators 4 and 10) which read an address indicating the track position of a photomagnetic disc 1 recorded in accordance with the ruggedness of the presence/absence of a tracking groove 20 of the photomagnetic disc 1 and move respective beams of two optical systems to prescribed positions are provided to specify irradiated positions of beams 3 and 9 accurately. Thus, only a part of the disc is easily and surely rewritten.
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