Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-10-23
2001-09-18
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044230, C369S119000, C369S120000
Reexamination Certificate
active
06292447
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a head 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, by changing incident angle of a beam which is incident on the objective optical system is controlled (i.e., a fine tracking is performed), 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. In order to control the galvano mirror to accurately perform the fine tracking, it is necessary to detect the amount of rotation of the galvano mirror.
Specifically, in a disc drive described above, if the deflection mirror is rotated to a position out of a certain rotational range to adjust the position of the beam spot, optical performance of the disc drive may be significantly lowered. Thus, the rotation angle of the deflection mirror should be monitored and controlled so as not to exceed a predetermined rotational range.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved head for an optical disc drive having a rotatable deflector, in which a rotation amount detection system is provided so that the tracking operation is performed accurately.
For the object, according to the invention, there is provided a head of an optical data recording/reproducing device, which is provided with: a laser source that emits a parallel laser beam; an objective optical system; a deflector rotatably provided between the laser source and the objective lens system, the laser beam emitted by the laser source being incident on the deflector and directed towards the objective optical system; a relay optical system provided between the deflector and the objective optical system, the relay optical system placing a position in the vicinity of a rotation axis of the deflector and a front principal plane of the objective lens to have a conjugate relationship; a detector provided between the deflector and the relay optical system, the detector having a first and a second light receiving portions and an opening, the two light receiving portions being arranged in a first direction in which the laser beam is deflected by the deflector, a part of the laser beam incident on the detector being received by the first and second light receiving portions, another part of the laser beam which passes through the opening being directed towards the objective lens through the relay optical system; and a controller that determines an amount of rotation of the deflector in accordance with amounts of light received by the two light receiving portions.
In one case, the first and second light receiving portions respectively include a first light receiving area and a second light receiving area. The first and second light receiving area and the opening are arranged along the first direction.
It is preferable that, at least in the first direction, a width of the opening is smaller than a length of a cross section of the laser beam incident on the detector.
Optionally, the opening may have a substantially circular shape.
Further optionally, the cross section of the laser beam incident on the detector may have a substantially elliptical shape having a longer axis in the first direction and a shorter axis in a second direction which is perpendicular to the first direction.
The longer axis of the elliptical shape should be greater than a diameter of the circular shape. It is preferable that the shorter axis of the elliptical shape is substantially the same as the diameter of the circular shape.
Still optionally, when the deflector is located at a predetermined position, the two light receiving areas receive the same amount of light.
In another case, the first light receiving portion may be provided with a first and a second light receiving areas, and the second light receiving portion comprises a third and fourth light receiving areas. In this case, the first and third light receiving areas are arranged in the first direction and provided on one side, in a second direction that is perpendicular to the first direction, of the opening, and the second and fourth light receiving areas are arranged in the first direction and provided on an opposite side, in the second direction, of the opening.
Optionally, the opening has a substantially rectangular shape, and the laser beam incident on the detector may have a substantially elliptical cross section which has a shorter axis in the first direction and a longer axis in the second direction.
In the above case, a width of the rectangular shape in the second direction should be smaller than the longer axis of the elliptical cross section of the laser beam.
Optionally, the width of the rectangular shape in the second direction may be substantially the same as a length of the shorter axis of the elliptical cross section of the laser beam.
In the above case, it is preferable that, when the deflector is located at a predetermined position, the first and third light receiving areas receive the same amount of light, and the second and fourth light receiving areas receive the same amount of light.
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), Owida
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: 4891998 (1990-01-01), Tourville
patent: 4959824 (1990-09-01), Ueda
patent: 4968876 (1990-11-01), Iima
patent: 5125750 (1992-06-01), Corle et al.
patent: 5126899 (1992-06-01), Kanazawa et al.
patent: 5136559 (1992-08-01), Nakayama
patent: 5151890 (1992-09-01), Yonekubo
patent: 5220550 (1993-06-01), Nakayama
patent: 5254893 (1993-10-01), Ide
patent: 5365504 (1994-11-01), Noguchi
patent: 5420848 (1995-05-01), Date et al.
patent: 5422872 (1995-06-01), Hsu et al.
patent: 5444683 (1995-08-01), Ishikawa
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: 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: 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: 62262017 (1987-11-01), None
patent: 64-2015 (1989-01-01), None
patent: 5128561 (1993-05-01), None
patent: 8315404 (1996-11-01), None
patent: 90/08363 (1990-07-01), None
patent: 98/06095 (1998-02-01), None
patent: 98/49684 (1998-11-01), None
patent: 98/49675 (1998-11-01), None
Patent Abstracts of Japan, vol. 012, No. 140 (P-696), dated Apr. 18, 1988.
Patent Abstracts of Japan, vol. 017, No. 505 (P-1611), dated Sep. 10, 1993.
An article entitled “Optical Magnetic Disk Device OfU.S. TeraStor Succeeds Tracking Control—Track Pitch O
Nishikawa Hiroshi
Takishima Suguru
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Huber Paul W.
LandOfFree
Head 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 Head for optical disc drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Head for optical disc drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2496793