| 摘要 |
PURPOSE:To suppress the generation of an edge shift in the detection of a bit edge by forming a first spot at the center position of an optical axis on an information memory carrier and second and third spots on both the sides in a direction parallel with a track. CONSTITUTION:Three spots are formed on an information memory carrier 14. The first spot has the center thereof on an optical axis and the second and third spots are arranged in a direction (direction A) parallel with a track sandwiching the first spot. Then, the first spot is used to perform a recording on the carrier 14 and a detection of a control signal for an optical head. Reflected light from the carrier 14 to the second and third spots is detected with 2-split photo detectors 18-1 and 18-2 separately and a differential detection is performed with a differential amplifier 19 for use in the reproduction of information. This eliminates effect of transmission characteristic of an optical head or the like in the detection of a bit edge. |
