Optical pickup and disc player

Details Optical pickup and disc player Optical pickup and disc player

1998-01-09

2000-08-01

Edun, Muhammad

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 4415, 369 4437, G11B 712

Patent

active

06097690&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to an optical pick-up adapted for carrying out write and read operations of information signals with respect to disc-shaped optical recording media such as an optical disc or a magneto-optical disc.
Further, this invention relates to a disc player adapted for carrying out recording and reproduction of information signals with respect to disc-shaped recording media such as an optical disc or a magneto-optical disc.
2. Description of Related Art
Hitherto, as a recording medium for information signals, disc-shaped optical recording media such as optical discs or magneto-optical discs have been proposed. Further, optical pick-up devices for carrying out write and read operations of information signals with respect to such disc-shaped optical recording media have been proposed. In addition, disc players having optical pick-ups and adapted for carrying out recording and reproduction of information signals with respect to disc-shaped optical recording media as described above have been proposed.
Such a disc-shaped optical recording medium has a structure including a transparent base (substrate) consisting of transparent material such as polycarbonate, and a signal recording layer deposited and formed on one principal surface portion of the transparent base. The optical pick-up includes a semiconductor laser serving as a light source, an object lens (objective) to which light beams emitted from the semiconductor laser are incident, and a photo-detector.
The light beams incident to the object lens are irradiated, in converged state, onto the signal recording surface of the disc-shaped optical recording medium by the object lens. In this case, these light beams are irradiated from the transparent base (substrate) side of the disc-shaped optical recording medium onto the disc-shaped optical recording medium, and are converged onto the signal recording surface which is the surface portion of the signal recording layer after being transmitted through the transparent base. This object lens is caused to undergo movement operation in the state supported by the bi-axial actuator to thereby converge the light beams onto the portion where information signal is recorded on the signal recording surface, i.e., a predetermined recording track. Such recording tracks are formed so as to take spiral shape on the principal surface portion of the disc-shaped optical recording medium.
In the disc-shaped optical recording medium, light beams are irradiated in the state converged after being passed through the object lens, whereby write or read operations of the information signal are carried out at the portion to which such light beams has been converged.
The light beam converged on the signal recording surface is caused to undergo modulation in light quantity or light polarization direction in dependency upon the information signal recorded on the signal recording surface and is reflected by the signal recording surface. The reflected light thus obtained returns to the object lens.
The reflected light beam reflected by the signal recording surface is received by the photo-detector after passed through the object lens. This photo-detector is a light receiving element such as a photo-diode, and serves to receive the reflected light beam which has been passed through the object lens to convert it into an electric signal. On the basis of the electric signal outputted from the photo-detector, reproduction of an information signal recorded on the disc-shaped optical recording medium is carried out.
Moreover, on the basis of the electric signal outputted from the photo-detector, a focus error signal indicating distance in the optical axis direction of the object lens between the focal point of the light beam by the object lens and the signal recording surface, and a tracking error signal indicating distance in the radial direction of the disc-shaped optical recording medium between the focal point and the recording track on the signal recording surface are generate

REFERENCES:
patent: 5216534 (1993-06-01), Boardman et al.
patent: 5673247 (1997-09-01), Sekimoto et al.

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