| 摘要 |
PURPOSE:To attain the high density recording with the high density of a pit- shaped memory element by detecting a diffracted light from the pit-shaped memory element with a divided photo detector and controlling an objective lens driving means with an output signal. CONSTITUTION:When the relative positions relation of a pit-shaped memory element 16 and a converging spot 20 is deviated, at the light quantity of diffracted lights 21a, 21b, 22a and 22b made incident on a detecting device 18 in accordance with the deviated direction, an unbalance occurs. For example, when the converging spot 20 is deviated only at an (x) direction left side, the light quantity of a primary diffracted light 21a made incident on a light detecting device 18 is increased and the light quantity of the primary diffracted light 21b is reduced. At this time, the unbalance does not occur at the light quantity of the diffracted lights 22a and 22b. Thus, from the unbalance of the output of light detecting devices 18a-18d, the relative position relation of the pit-shaped memory element 16 and the converging spot 20 can be detected and the high density recording can be executed.
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