Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-10-29
2001-12-25
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044190
Reexamination Certificate
active
06333910
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical system to be employed in an optical disc drive to read/write data from/to an optical disc.
Recently, technology in the field of magneto-optical disc drives has been greatly improved such that a data recording density on a magneto-optical disc has reached in excess of 10 Gbits/inch
2
.
In such an optical disc drive, an objective optical system is mounted on an arm which is movable in a transverse direction of tracks formed on an optical disc for rough tracking. Firstly, the rough tracking is performed to locate the optical head in the vicinity of the track. Then, an incident angle of a beam incident on the objective optical system is changed to locate a spot of beam formed by the objective optical system for fine tracking, with use of a galvano mirror or the like. During the fine tracking operation, the beam spot is accurately located on one of the tracks whose pitch is, for example, 0.34 &mgr;m. When the beam spot is moved on the disc surface, i.e., when the incident angle of the beam incident on the objective optical system is being changed, it is preferable that an intensity distribution of the beam does not vary on the disc surface. In other words, it is preferable that, in such an optical system, a coupling efficiency of a light beam traveling between the objective optical system and a light source applicable to the optical disc drive is relatively high.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved optical system, which is applicable to an optical disc drive having a rotatable deflection system, and has a relatively high coupling efficiency between a light source and an objective optical system.
According to an aspect of the invention, there is provided an optical system for an optical disc drive, which is provided with: a laser source that emits a laser beam; an objective lens that receives the laser beam and converges the laser beam on an optical disc; a deflection mirror provided between the laser source and the objective lens, the deflection mirror being rotatable about a rotation axis, the laser beam emitted by the laser source being reflected by the deflection mirror and directed toward the objective lens, the laser beam proceeding from the deflection mirror toward the objective lens proceeding in a direction parallel to an optical axis of the optical system when the deflection mirror is located at a neutral position; a first driver which rotates the deflection mirror; a rotation amount detecting system that detects a rotation angle of the deflection mirror with respect to the neutral position; and a second driver which moves the deflection mirror in a direction along which the laser beam is incident, from the laser source, onto the deflection mirror, the second driver moving the deflection mirror. With this construction, it becomes possible that the laser beam deflected by the deflection mirror is incident on the objective optical system substantially at the same position regardless of rotation amount of the deflection mirror.
In particular, the second driver moves the deflection mirror in accordance with the rotation angle of the deflection mirror.
Specifically, an amount (h) of movement of the deflection mirror is determined based on an equation below:
h=L tan(2&thgr;),
wherein, L represents a distance between the deflection mirror and the objective optical system, and &thgr; represents the rotation angle of the deflection mirror.
In one case, the objective optical system is movable in a transverse direction of tracks formed on the optical disc, and the distance between the laser source and the objective optical system may be changeable. Alternatively, the distance between the laser source and the objective optical system may be constant.
Optionally, the rotation axis of the deflection mirror extends perpendicular to a surface of the optical disc, and the second driver moves the deflection mirror in a direction parallel to the surface of the optical disc. Alternatively, the rotation axis of the deflection mirror extends in parallel with a surface of the optical disc, and wherein the second driver moves the deflection mirror in a direction perpendicular to the surface of the optical disc. Further alternatively, the rotation axis of the deflection mirror extends in parallel with a surface of the optical disc, and the second driver moves the deflection mirror in a direction parallel to the surface of the optical disc.
According to another aspect of the invention, there is provided a method of deflecting, by means of a deflection mirror, a light beam emitted by a light source towards an objective optical system of an optical head for an optical disc drive, which includes the steps of rotating the deflection mirror, and moving the deflection mirror in a direction along which the light beam emitted by the light source is incident on the deflection mirror such that the laser beam deflected by the deflection mirror is incident on the objective optical system substantially at the same position regardless of rotation amount of the deflection mirror.
Specifically, an amount (h) of movement of the deflection mirror is determined based on an equation below:
h=L tan(2&thgr;),
wherein, L represents a distance between the deflection mirror and the objective optical system, and &thgr; represents the rotation angle of the deflection mirror. In a particular case, the objective optical system is movable in a transverse direction of tracks formed on the optical disc, and the distance between the light source and the objective optical system may be changeable. Alternatively, the distance between the light source and the objective optical system may be constant.
REFERENCES:
patent: 2750461 (1956-06-01), Bunch
patent: 3244917 (1966-04-01), Gute
patent: 3354833 (1967-11-01), Laing
patent: 4088914 (1978-05-01), Aoki
patent: 4126796 (1978-11-01), Ito
patent: 4206379 (1980-06-01), Owda
patent: 4285566 (1981-08-01), Yamamoto
patent: 4297713 (1981-10-01), Ichikawa et al.
patent: 4351596 (1982-09-01), Ohniwa et al.
patent: 4466088 (1984-08-01), Trethewey
patent: 4744071 (1988-05-01), Bricot et al.
patent: 4891998 (1990-01-01), Tourville
patent: 4959824 (1990-09-01), Ueda et al.
patent: 4968876 (1990-11-01), Iima
patent: 5125750 (1992-06-01), Corle et al.
patent: 5126899 (1992-06-01), Kanazawa
patent: 5136559 (1992-08-01), Nakayama
patent: 5151890 (1992-09-01), Yonekubo
patent: 5220550 (1993-06-01), Nakayama
patent: 5253245 (1993-10-01), Rabedeau
patent: 5254893 (1993-10-01), Ide
patent: 5289444 (1994-02-01), Tanaka
patent: 5365504 (1994-11-01), Noguchi
patent: 5383174 (1995-01-01), Numata et al.
patent: 5420848 (1995-05-01), Date et al.
patent: 5422872 (1995-06-01), Hsu et al.
patent: 5444683 (1995-08-01), Ishikawa et al.
patent: 5461498 (1995-10-01), Iwao
patent: 5517474 (1996-05-01), Takamine
patent: 5532480 (1996-07-01), Scofield
patent: 5564585 (1996-10-01), Saitoh
patent: 5596446 (1997-01-01), Plesko
patent: 5608280 (1997-03-01), Tamemoto et al.
patent: 5610752 (1997-03-01), Hayakawa
patent: 5625244 (1997-04-01), Bradfield
patent: 5684762 (1997-11-01), Kubo
patent: 5705868 (1998-01-01), Cox et al.
patent: 5719834 (1998-02-01), Futagawa et al.
patent: 5764613 (1998-06-01), Yamamoto
patent: 5768241 (1998-06-01), Kanazawa et al.
patent: 5844676 (1998-12-01), Southam et al.
patent: 5886438 (1999-03-01), Kawanishi
patent: 5920140 (1999-07-01), Nakagishi et al.
patent: 6055221 (1999-03-01), Ikegame
patent: 0084727 (1983-08-01), None
patent: 0084728 (1983-08-01), None
patent: 0448362 (1991-09-01), None
patent: 0790512 (1997-08-01), None
patent: 0907163 (1999-04-01), None
patent: 907163 (1999-04-01), None
patent: 378922 (1932-08-01), None
patent: 1314002 (1973-04-01), None
patent: 1457995 (1976-12-01), None
patent: 2000604 (1979-01-01), None
patent: 2086092 (1982-05-01), None
patent: 2193341 (1988-02-01), None
patent: 62-262017 (1987-11-01), None
patent: 64-2015 (1989-01-01), None
patent: 5-128561 (1993-05-01), None
patent: 5128561 (1993-05-01), None
patent: 831540
Nishikawa Hiroshi
Takishima Suguru
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Hindi Nabil
LandOfFree
Optical system for optical disc drive 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 system for optical disc drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical system for optical disc drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561001