| 摘要 |
PROBLEM TO BE SOLVED: To discriminate kinds of two or more kinds of optical disks having same size of pits, thickness of disk substrates, and track pitches and having almost same length of data written on them, but having different optical disk formats. SOLUTION: The optical disk to be discriminated has information track meandered and formed in a track direction (a) of the track with a meandering frequency decided according to its kind. A laser beam is irradiated to the information track, while rotating this optical disk at predetermined velocity, and the reflected lights are detected with photodetectors divided in two in the direction (a) of the track. Push-pull detection which inputs two output currents of these half-divided photodetectors into an operational amplifier, and takes those differences is performed. An output signal of the operational amplifier obtained by push-pull detection is a meandering signal, and the kind of the optical disk can be discriminated by detecting the frequency (meandering frequency) of this meandering signal.
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