Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-11-05
2001-07-10
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044320
Reexamination Certificate
active
06259665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk recording/reproducing apparatus for recording and/or reproducing an information signal onto/from an optical information recording medium such as an optical disk and more particularly to an optical disk recording/reproducing apparatus with a tilt sensor for detecting a tilt between the optical information recording medium and an objective lens.
2. Description of the Related Art
In recent years, the demand for high density recording to handle a high precision still picture, a video and the like, by an optical information recording medium such as an optical disk and digital versatile disk (DVD) has increased in the information recording and reproducing field. To enable such high precision recording, an optical disk recording/reproducing apparatus capable of realizing a large capacity recording is desired.
Examples of methods to achieve this requirement, include selecting a laser source with a shorter wavelength equipped with an optical pickup unit, and reducing a diameter of a beam spot by increasing the numerical aperture (NA) of the objective lens.
However, if the beam spot diameter is reduced or when the disk track pitch is increased in density, the interference of information signal between a track presently accessed and the adjacent tracks increases, that is, the “crosstalk”, or an interference between adjacent signals in the same track increases. These interferences are generated due to a relative tilt between an optical axis of the objective lens of the optical pickup unit and the optical information recording medium (hereinafter referred to as “tilt”). As a result, accurate recording and reproducing of an information signal with respect to the optical information recording medium can not be obtained.
The relationship between an allowance value &thgr; relative to the tilt, a laser wavelength &lgr; and a numerical aperture NA is expressed as follows:
&thgr;∝&lgr;/(NA)
3
(Equation 1)
Therefore, it is necessary to achieve an accurate tilt servo for a high density recording of the disk. Also, the optical disk recording/reproducing apparatus must be provided with a tilt detector capable of detecting an accurate tilt amount while recording and reproducing the information.
SUMMARY OF THE INVENTION
The present invention solves the above problems. One purpose of the invention is to provide an optical disk recording/reproducing apparatus capable of detecting an accurate tilt amount while recording and/or reproducing.
To achieve the above object, the present invention provides an optical recording/reproducing apparatus for recording/reproducing information onto/from an optical recording medium, comprising an optical element for condensing a light beam onto the recording medium; and a detector coupled to the optical element for detecting a tilt condition between the recording medium and the optical element, wherein the detector irradiates a detection beam onto the recording medium through the optical element, and detects the detection beam reflected by the recording medium through the optical element. The optical recording/reproducing apparatus includes a driver for driving the optical element in a direction relative to a surface of the recording medium; and a controller for controlling the driver based on the reflected detection beam received by the detector.
According to the invention, a holder holds the optical element. The holder includes a first unit for holding the optical element and a second unit for holding the detector. The optical element has a first optical surface facing the recording medium and a second optical surface facing the detector.
In one embodiment of the invention, the optical element includes an objective lens. In another embodiment of the invention, the detector includes an optical sensor.
According to a preferred embodiment of the present invention, a first axis drawn along a direction of the irradiated detection beam, and a second axis drawn along a direction of the reflected direction beam are such that a plane parallel to the first axis and the second axis is perpendicular to a surface of the recording medium.
According to the present invention, the detector comprises of an emission element for emitting the irradiated detection beam, and a detection element for detecting the reflected detection beam. In the present invention, the emission element and the detection element face a peripheral region of an optical surface of the optical element.
In accordance with another aspect of the invention, a position on the recording medium where the light beam is condensed is a target position for the irradiated detection beam.
According to the invention, an electromagnetic element generates the electromagnetic force to drive the optical element.
In accordance with a further aspect of the invention, a third axis drawn between the emission element and the detection element is parallel to a radial direction of the recording medium.
In accordance with yet another aspect of the invention, the third axis drawn between the emission element and the detection element is perpendicular to a radial direction of the recording medium.
Another embodiment of the invention relates to, an optical recording/reproducing apparatus for recording/reproducing information onto/from an optical recording medium, comprising an optical element for condensing the light beam onto the recording medium; and a detector coupled to the optical element for detecting a tilt condition between the recording medium and the optical element, the detector emitting a detection beam onto a position on the recording medium having a target position of a condensed light beam, and receiving the detection beam reflected by the recording medium.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5206848 (1993-04-01), Kusano et al.
patent: 5216649 (1993-06-01), Koike et al.
patent: 5596557 (1997-01-01), Matsumoto
patent: 5978332 (1999-11-01), Itakura et al.
patent: 7-262585 (1995-10-01), None
patent: 7-272300 (1995-10-01), None
Foley & Lardner
Huber Paul W.
Kabushiki Kaisha Toshiba
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