Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1996-08-23
1999-07-13
Huber, Paul W.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 94, 369 4437, G11B 700
Patent
active
059236329
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical pickup device for use in a recording and/or reproducing apparatus capable of recording an information signal on a so-called multi-layer optical disc having a plurality of information layers and/or reproducing the information signal from respective information storage layers of the multi-layer optical disc.
BACKGROUND ART
Optical pickup devices used in conventional recording and/or reproducing apparatuses in which an optical disc is used as a recording medium, includes a semiconductor laser as a light source for emitting a light beam, a collimator lens which is disposed between the semiconductor laser and the optical disc and whose optical axis is aligned with optical axes of the semiconductor laser and the optical disc, a diffraction grating, a polarizing beam splitter and an objective lens. The optical pickup device further includes a photodetector for receiving a light beam from the optical disc, and a focusing lens which is disposed between the photodetector and the polarizing beam splitter and whose optical axis is aligned with optical axes of the photodetector and the polarizing beam splitter.
In such conventional optical pickup devices, the light beam is emitted from the semiconductor laser and transmitted through the polarizing beam splitter and an objective lens so as to be radiated and focused onto an information signal storage layer of the optical disc. The light beam reflected from the optical disc is received by the photodetector.
The optical disc used as a recording medium for a recording and/or reproducing apparatus in which the afore-mentioned optical pick-up is incorporated and which is adapted to record an information signal thereon and/or reproduce the signal therefrom, generally includes a substrate made of a transparent synthetic resin material such as polycarbonate or polymethyl-methacrylate, an information signal layer formed on a main surface of the substrate, and a protecting layer formed over the information signal layer to protect the layer against chemical erosion or mechanical damage.
Such an optical disc has been produced by using various shaping methods such as a thermal pressure-molding method or a thermal casting method. When subjected to the shaping method, the optical disc is likely to suffer from undesired warpage or corrugation due to a thermal distortion generated therein. Consequently, a dislocation of the information signal storage layer occurs in the direction perpendicular to the main surface of the disc. Further, the circularity of tracks formed on the information signal layer is adversely affected. When the optical disc is rotated to reproduce the information signal stored on the information signal layer, the surface of the information signal layer and the tracks thereon suffer from undesirable oscillation and deflection.
Accordingly, in order to achieve an accurate read-out or reproduction of the information signal stored on a signal recording region of the optical disc without being adversely affected by the oscillation of the optical disc surface and the deflection of the tracks, the optical pickup device is provided with a focusing control function for conducting an adequate focusing adjustment of the objective lens in response to a degree of the eventual oscillation of the surface of the optical disc, and a tracking control function for performing an adequate tracking adjustment of the objective lens so as to follow the oscillation of a signal track formed on the signal recording region of the optical disc.
Meanwhile, there has been a demand for higher density information storage, so that proposals have been made to provide a multi-layer optical disc having a multiple of information signal layers arranged in an overlapped relation to each other. The multi-layer optical disc conventionally known is of a two-layer type having two overlapped information signal layers.
The two-layer type optical disc 5 includes, as shown in FIG. 1, a disc substrate 5C made of a transparent synthetic resin material su
REFERENCES:
patent: 5097464 (1992-03-01), Nishiuchi et al.
patent: 5563873 (1996-10-01), Ito et al.
Fukumoto Atsushi
Kato Yoshiaki
Huber Paul W.
Kananen Ronald P.
Sony Corporation
LandOfFree
Optical pick-up device for a multi-layer recording medium with a does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical pick-up device for a multi-layer recording medium with a, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical pick-up device for a multi-layer recording medium with a will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2283283