| 摘要 |
PURPOSE:To attain simultaneous access on both sides of a photomagnetic medium by setting two pairs of double beam optical heads alternately and opposite to each other in the radius direction of the photomagnetic medium. CONSTITUTION:An external magnetic field generator 14 which is paired with objective lenses 13 and 23 is set at the tip part 11 of an arm 10 at one side on a straight line against the radius direction (arrow head C) of a photomagnetic medium 1. The lens 13 condenses a beam on the surface of the medium 1, and the lens 23 condenses a light beam on the rear side of the medium 1. While the lens 23 and an external magnetic field generator 24 are set at the tip part 21 of the other arm 20. Thus the lens 13 and the generator 24 and the lens 23 and the generator 14 are set oppositely to each other respectively centering on the medium 1. Then no error is produced in such the positional relation.
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