Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1997-06-18
1999-10-19
Tran, Thang V.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 58, 369 4432, 369 4427, G11B 700, G11B 1920
Patent
active
059700351
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical disc driving device whereby plural sorts of the optical discs different in design formats, such as recording capacity, can be selectively employed.
BACKGROUND ART
Up to now, an optical disc enabling information signals to be recorded and/or reproduced using an optical beam has been used. Among the optical discs of this sort in use, there are a read-only compact disc (CD) having pre-recorded music data or information data to be processed by a computer, and a CD-ROM.
There have also been proposed a high-density (HD) disc or a high density (HD)-CD-ROM having the recording density twice or three times as high as that of the CD or CD-ROM having the standard recoding density.
There is also proposed a digital versatile disc/digital video disc (DVD) as an optical disc having the same size as but having the recording density seven to eight times as high as the CD or the CD-ROM.
Also in use is a magneto-optical disc which is a recording/reproducing optical disc having the same size as the CD or CD-ROM and capable of re-recording data signals.
An optical disc drive device, having the above optical discs as a recording medium, has a disc table which is run in rotation by a spindle motor and in which the optical disc is set in a horizontal position. The signal recording surface of the optical disc, thus rotated, is scanned across its inner and outer rims by a light beam radiated from an optical pickup for recording/reproducing data on or from the optical disc. The light beam radiated from the optical pickup is radiated perpendicularly on the signal recording surface of the optical disc as it is converged for being focused on the signal recording surface.
For recording and/or reproducing data on or from the optical disc with satisfactory recording/reproducing characteristics, it is desirable that the light beam radiated from the optical pickup be incident perpendicularly on the signal recording surface of the optical disc. With the light beam being incident perpendicularly on the signal recording surface of the optical disc, a beam spot of the light beam converged by the objective lens for being radiated on the signal recording surface of the optical disc becomes truly circular, as a result of which the beam spot can correctly scan a recording track formed on the signal recording surface of the optical disc for recording and/or reproducing data with good recording/reproducing characteristics.
Meanwhile, in consideration of warping of an optical disc and mounting accuracy of a spindle motor or an optical pickup, a pre-set allowance is provided in an optical disc driving device employing an optical disc as a recording medium by a standard with respect to a relative tilt between the signal recording surface of the optical disc and the optical axis of the objective lens converging and radiating the light beam on the optical disc.
For example, in an optical disc driving device employing an optical disc, such as a CD or CD-ROM 12 cm in diameter, as a recording medium, the allowance of the relative tilt between the optical axes of the optical disc and the objective lens is unified at 1.2.degree. or less. That is, the relative tilt of 1.2.degree. or less between the optical axis of the optical disc and that of the objective lens with respect to the optical axis of the objective lens perpendicular to the signal recording surface of the optical disc is allowed. Specifically, the allowance of the tilt of the objective lens is set to 0.6.degree. or less, while that of the spindle motor or of the objective lens on the device is set to 0.6.degree. or less.
On the other hand, with an optical disc, such as HD-CD or HD-CD-ROM, having a recording density higher than that of a CD or a CD-ROM having a standard recording density, not only the recording track for data recording is reduced in width, but also the track pitch is reduced for increasing the recording density per unit area for improving the recording density.
In an optical disc drive device employing the optical disc of such
REFERENCES:
patent: 4918678 (1990-04-01), Dolby
patent: 5056075 (1991-10-01), Maruta et al.
patent: 5729510 (1998-03-01), Kasahara et al.
Ohmori Kiyoshi
Seto Hidekazu
Sony Corporation
Tran Thang V.
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