| 摘要 |
PURPOSE:To always set automatically the light volume of laser beam suited to the characteristic of a photosensitive material of an optical disk, by storing previously the record/reproduction conditions peculiar to the optical disk on said optical disk and then reading said conditions automatically when the use of the optical disk starts. CONSTITUTION:Type marks 9a, 9b and 9c which can be detected optically or magnetically are provided at the fringe area of the data non-recording region 6 of an optical disk 11. a disk type discriminating circuit 16 produces a code which specifies the type on the basis of marks 9a, 9b, 9c- detected by a type mark sensor 15. A holding circuit 17 holds the produced type code while the disk 11 is in use, and then this type code is converted by a D/A converter 18 into an analog level corresponding to the light volume level at the base point of the disk 11. This converted code of an analog level is supplied to a laser diode 21 via a differential amplifier 19 and a driver 20. As a result, the output beam of a laser diode 21 is set at a light volume level suited to the photosensitive material of the disk 11 through a pickup head 13. |
