| 摘要 |
PROBLEM TO BE SOLVED: To properly discriminate disk sizes. SOLUTION: Disk physical information is read out of the optical disk recorded with the disk physical information on the disk surface of the optical disk, and the optical disk is discriminated in accordance with this disk physical information, while the optical disk is rotated at a standard rotating speed. The speed when the optical disk is rotated at a high speed, according to this discriminated optical disk is limited. The size, etc., of the disk are discriminated by utilizing the disk physical information recorded on the disk or measuring the inertia of the disk or the light reflectivity of the disk and the rotating speed of the disk is controlled to an adequate value or below in accordance with this discrimination output. The diameters and shapes of the mounted optical disks may be discriminated exactly, when the various optical disks, such as the optical disks, having a diameter (8 cm) smaller than those of the optical disks having a standard diameter (12 cm) in addition the optical disks, having a standard diameter or the optical disks having a rectangular shape, are mounted at the device.
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