US4812637A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical disc head with high signal-to-noise ratio
Assignee: Brother Industries Ltd
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Filing: 1987-06-24
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Granted: 1989-03-14
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Expires: 2007-06-24
Abstract
Abstract An optical head for an optical disc or for a magneto-optical disc for reading out information recorded thereon, including a light source for emitting a beam of linearly polarized light toward the disc, at least one Faraday rotator for passing the emitted beam and rotating a plane of polarization of the beam by a predetermined angle, at least one beam splitter for either passing or reflecting the incident light depending upon the plane of polarization, and a light sensor for sensing a light reflected by the splitter. Some combinations and configurations of these beam splitters and Faraday rotators are exemplified. This head is designed to be easily assembled and to effectively detect a light reflected by the optical disc, thereby providing reliable detection of data recorded thereon.
Inventors
- 👤 Kazunari Taki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 01:15
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1365
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
131 words
A disc head for an optical disc comprising: a light source for emitting a beam of light toward an optical disc; a Faraday rotator, which is disposed between the light source and the optical disc, for rotating a plane of polarization of the light beam emitted from the light source by 45°; a beam splitter, which is disposed between the Faraday rotator and the light source, for passing a component with a specific plane of polarization of the light beam emitted from the light source, and for reflecting a light beam with a plane of polarization perpendicular to the specific plane of polarization which has again passed the Faraday rotator after being reflected by the optical disc; and a light sensor for sensing a light beam reflected by the beam splitter.
Claim 2
Dependent Claim
131 words
A disc head for an optical disc comprising: a light source for emitting a beam of light toward an optical disc; a Faraday rotator, which is disposed between the light source and the optical disc, for rotating a plane of polarization of the light beam emitted from the light source by 45°; a beam splitter, which is disposed between the Faraday rotator and the light source, for passing a component with a specific plane of polarization of the light beam emitted from the light source, and for reflecting a light beam with a plane of polarization perpendicular to the specific plane of polarization which has again passed the Faraday rotator after being reflected by the optical disc; and a light sensor for sensing a light beam reflected by the beam splitter.
Claim 3
Dependent Claim
31 words
A disc head for an optical disc according to claim 1, wherein the optical disc stores information by means of a change in a reflectance of a surface of a disc.
Claim 4
Dependent Claim
193 words
A disc head for a magneto-optical disc comprising: a light source for emitting a beam of linearly polarized light toward a magneto-optical disc; a first beam splitter, which is disposed between the light source and the magneto-optical disc, for passing a component with a specific plane of polarization of the light beam emitted from the light source and for reflecting a light beam with a plane of polarization perpendicular to the specific plane of polarization; a first Faraday rotator, which is disposed between the first beam splitter and the magneto-optical disc, for rotating a plane of polarization of the light beam that has passed the first beam splitter by 45°; a second beam splitter, which is disposed between the first Faraday rotator and the magneto-optical disc, for passing the light beam that has passed the first Faraday rotator and for reflecting the light beam with a plane of polarization perpendicular to the plane of polarization of the light beam that has passed the first Faraday rotator; and first and second light sensors provided for sensing the light reflected from the first and second beam splitters respectively after being reflected by the optical disc.
Claim 5
Dependent Claim
193 words
A disc head for a magneto-optical disc comprising: a light source for emitting a beam of linearly polarized light toward a magneto-optical disc; a first beam splitter, which is disposed between the light source and the magneto-optical disc, for passing a component with a specific plane of polarization of the light beam emitted from the light source and for reflecting a light beam with a plane of polarization perpendicular to the specific plane of polarization; a first Faraday rotator, which is disposed between the first beam splitter and the magneto-optical disc, for rotating a plane of polarization of the light beam that has passed the first beam splitter by 45°; a second beam splitter, which is disposed between the first Faraday rotator and the magneto-optical disc, for passing the light beam that has passed the first Faraday rotator and for reflecting the light beam with a plane of polarization perpendicular to the plane of polarization of the light beam that has passed the first Faraday rotator; and first and second light sensors provided for sensing the light reflected from the first and second beam splitters respectively after being reflected by the optical disc.
Claim 6
Dependent Claim
18 words
A use of the disc head according to claim 3 for a disc head of an optical disc.
Claim 7
Dependent Claim
89 words
A disc head for a magneto-optical disc according to claim 3, wherein: the disc head further comprises a third beam splitter for splitting the light beam reflected by the first beam splitter after being reflected by the disc; the second light sensor receives the light beams from the second beam splitter and from the third beam splitter to generate a signal representative of information on the disc; and the first light sensor receives the light beam from the third beam splitter to generate a focusing and/or tracking control signal.
Claim 8
Dependent Claim
50 words
A disc head for a magneto-optical disc according to claim 3, wherein the disc head further comprises a second Faraday rotator disposed between the second beam splitter and the magneto-optical disc for rotating a plane of polarization of an incident light beam by 45° plus or minus a small angle.
Claim 9
Dependent Claim
56 words
A disc head for a magneto-optical disc according to claim 3, wherein the disc head further comprises a second Faraday rotator disposed between the second beam splitter and the magneto-optical disc for rotating a plane of polarization of an incident light beam by an angle selected from the group consisting of 22.5°, 67.5°, 112.5° and 157.5°.
Claim 10
Dependent Claim
37 words
A disc head for a magneto-optical disc according to claim 6, wherein the second light sensor generates a focusing and/or tracking control signal and the first light sensor generates a signal representative of information on the disc.
Claim 11
Dependent Claim
42 words
A disc head for a magneto-optical disc according to claim 7, wherein the disc head further comprises an adder by which signals generated by the first and second light sensors are added to generate a signal representative of information on the disc.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-13 | 1992-09-12 | 1993-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-13 | 1996-09-12 | 1997-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-13 | 2000-09-12 | 2001-03-14 | $7700.00 | Window Closed / Lapsed |