EP0305169A2
Expired / Lapsed
EP
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Optical pickup apparatus and optical grating assembly therefor
Assignee: Sharp Corp
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Filing: 1988-08-24
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Granted: —
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Expires: 2008-08-24
Abstract
Abstract An optical pickup apparatus for optically reading the data stored in a flat information carrier disc (7) in the form of tiny pits. The pickup apparatus directs a beam of light from a light source (1) to the disc surface. The impinging beam is modulated by the data pits and reflected back to a photodetector (8). A novel optical grating assembly (2) is disposed between the light source (1) and the information disc (7), and comprises a diffraction grating (4a) for the light beam from the source and a holographic grating (3) for directing part of the light beam reflected by the disc to the photodetector (8). The diffraction and holographic grating (4a, 3) are formed integral with each other into the grating assembly(2).
Inventors
- 👤 Yukio Kurata
- 👤 Hiroshi Ogata
- 👤 Hikaru Nishihara
- 👤 Mitsuharu Tomura
- 👤 Shigeki Tsuji
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 00:58
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1353; G11B7/08; G11B7/09; G11B7/0901; G11B7/0903; G11B7/0908; G11B7/0909; G11B7/0916; G11B7/1381
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
119 words
An optical pickup apparatus for reading data pits held in a disc, which converges a light beam from a source of light into a light spot on said disc and directs the light reflected by said disc to a photodetector for producing a tracking error signal, comprising: first grating means for distributing the light beam from said source of light into a main beam for reading said data pits on said disc and a pair of sub-beams for sensing tracking error of said main beam; and second grating means for orienting part of the light beam reflected by said disc to said photodetector, said first and second grating means being formed integral with each other into a grating assembly.
Claim 2
Dependent Claim
119 words
An optical pickup apparatus for reading data pits held in a disc, which converges a light beam from a source of light into a light spot on said disc and directs the light reflected by said disc to a photodetector for producing a tracking error signal, comprising: first grating means for distributing the light beam from said source of light into a main beam for reading said data pits on said disc and a pair of sub-beams for sensing tracking error of said main beam; and second grating means for orienting part of the light beam reflected by said disc to said photodetector, said first and second grating means being formed integral with each other into a grating assembly.
Claim 3
Dependent Claim
26 words
An optical pickup apparatus according to claim 1, wherein said oriented beam is detected by said photodetector through the astigmatic method to produce focusing error signals.
Claim 4
Dependent Claim
31 words
An optical pickup apparatus according to claim 1, wherein said oriented beam from said grating assembly is detected by said photodetector through the wedge prism method to produce focusing error signals.
Claim 5
Dependent Claim
47 words
An optical pickup apparatus according to claim 1, wherein said optical grating assembly comprises a first surface portion facing to said source of light and provided with said first grating means, and a second surface portion facing to said disc and provided with said second grating means.
Claim 6
Dependent Claim
17 words
An optical pickup apparatus according to claim 1, wherein said first grating means comprises a diffraction grating.
Claim 7
Dependent Claim
17 words
An optical pickup apparatus according to claim 1, wherein said second grating means comprises a holographic grating.
Claim 8
Dependent Claim
17 words
An optical pickup apparatus according to claim 1, wherein said optical grating assembly is made of glass.
Claim 9
Dependent Claim
17 words
An optical pickup apparatus according to claim 1, wherein said optical grating assembly is made of plastics.
Claim 10
Dependent Claim
42 words
An optical pickup apparatus according to claim 4, wherein said optical grating assembly is provided with lens means for enhancing astigmatism in its first surface portion in an area where the light beam oriented by said grating means to said photodetector passes.
Claim 11
Dependent Claim
20 words
An optical pickup apparatus according to claim 9, wherein said lens means for enhancing astigmatism comprises a cylindrical lens surface.
Claim 12
Dependent Claim
44 words
An optical pickup apparatus according to claim 4, wherein said optical grating assembly is provided with lens means for magnifying light spots in said first surface portion in an area where the light beam oriented by said second grating means to said photodetector passes.
Claim 13
Dependent Claim
22 words
An optical pickup apparatus according to claim 11, wherein said lens means for magnifying said light spots comprises a concave lens surface.
Claim 14
Dependent Claim
29 words
An optical pickup apparatus according to claim 6, wherein said holographic grating is divided into two sections in order to obtain focusing error signals through the wedge prism method.
Claim 15
Dependent Claim
37 words
An optical pickup apparatus according to claim 6, wherein said holographic grating has an additional function of relieving influence of astigmatism or coma in the light beam reflected by said disc and transmitted through said grating assembly.
Claim 16
Dependent Claim
25 words
An optical pickup apparatus according to claim 6, wherein said holographic grating has an additional function of magnifying the light spots formed on said photodetector.
Claim 17
Dependent Claim
33 words
An optical pickup apparatus according to claim 6, wherein said holographic grating has an additional function of enhancing astigmatism in the light beam reflected by said disc and transmitted through said grating assembly.
Claim 18
Dependent Claim
39 words
An optical pickup apparatus according to claim 13, wherein said holographic grating is divided into two sections along a line which extends parallel to the grating lines of said diffraction grating provided in one face of said grating assembly.
Claim 19
Dependent Claim
105 words
An optical grating assembly to be disposed between a source of light and an information carrying disc for orienting part of the light beam reflected by the disc to a photodetector comprising: a first surface portion facing to said source of light; a second surface portion facing to said information carrying disc; first grating means provided on said first surface portion for diffracting a light beam from said light source into a zero-order beam and a pair of first order beams; and second grating means provided on said second surface portion for orienting part of the light beam reflected by said disc to said photodetector.
Claim 20
Dependent Claim
105 words
An optical grating assembly to be disposed between a source of light and an information carrying disc for orienting part of the light beam reflected by the disc to a photodetector comprising: a first surface portion facing to said source of light; a second surface portion facing to said information carrying disc; first grating means provided on said first surface portion for diffracting a light beam from said light source into a zero-order beam and a pair of first order beams; and second grating means provided on said second surface portion for orienting part of the light beam reflected by said disc to said photodetector.
Claim 21
Dependent Claim
17 words
An optical grating assembly according to claim 18, wherein said first grating means comprises a diffraction grating.
Claim 22
Dependent Claim
17 words
An optical grating assembly according to claim 18, wherein said second grating means comprises a holographic grating.
Claim 23
Dependent Claim
17 words
An optical grating assembly according to claim 18, wherein said optical grating assembly is made of glass.
Claim 24
Dependent Claim
17 words
An optical grating assembly according to claim 18, wherein said optical grating assembly is made of plastics.
Claim 25
Dependent Claim
40 words
An optical grating assembly according to claim 18, wherein said lens means for enhancing astigmatism is provided in said first surface portion and in an area where the light beam oriented by said second grating means to said photodetector passes.
Claim 26
Dependent Claim
20 words
An optical grating assembly according to claim 23, wherein said lens means for enhancing astigmatism comprises a cylindrical lens surface.
Claim 27
Dependent Claim
44 words
An optical grating assembly according to claim 18, further comprising lens means for magnifying the light spots formed on said photodetector provided in said first surface portion in an area where the light beam oriented by said second grating means to said photodetector passes.
Claim 28
Dependent Claim
22 words
An optical grating assembly according to claim 25, wherein said lens means for magnifying the light spots comprises a concave lens surface.
Claim 29
Dependent Claim
39 words
An optical grating assembly according to claim 20, wherein said holographic grating is divided into two sections in order to divide the light beam reflected by said disc and impinging on said holographic grating into two first-order diffracted beams.
Claim 30
Dependent Claim
36 words
An optical grating assembly according to claim 20, wherein said holographic grating has an additional function of relieving influence of astigmatism or coma in the light beam reflected by said disc and transmitted through said grating.
Claim 31
Dependent Claim
25 words
An optical grating assembly according to claim 20, wherein said holographic grating has an additional function of magnifying the light spots formed on said photodetector.
Claim 32
Dependent Claim
31 words
An optical grating assembly according to claim20, wherein said holographic grating has an additional function of enhancing astigmatism in the light beam reflected by said disc and transmitted through said grating.
Claim 33
Dependent Claim
42 words
An optical grating assembly according to claim 27, wherein said holographic grating is divided into two sections along a line which extends parallel to the grating lines of said diffraction grating provided in said first surface portion of said optical grating assembly.
Claim 34
Dependent Claim
123 words
An optical apparatus for reading information recorded on a track or tracks on a recording medium (7) by causing a focussed light spot (9b) to scan along said track or tracks and detecting light from the medium, first grating means (4a) being provided for deriving from a source light beam (9) a main beam (9a) which is focussed to form said focussed light spot, and a pair of sub-beams (10a, 11a) which are focussed onto the recording medium for use in detecting tracking error of the mainbeam, and second grating means (3) being provided for directing light reflected from the recording medium toward a photodetector (8), characterised in that said first and second grating means are integrally formed into a grating assembly (2).
Claim 35
Dependent Claim
123 words
An optical apparatus for reading information recorded on a track or tracks on a recording medium (7) by causing a focussed light spot (9b) to scan along said track or tracks and detecting light from the medium, first grating means (4a) being provided for deriving from a source light beam (9) a main beam (9a) which is focussed to form said focussed light spot, and a pair of sub-beams (10a, 11a) which are focussed onto the recording medium for use in detecting tracking error of the mainbeam, and second grating means (3) being provided for directing light reflected from the recording medium toward a photodetector (8), characterised in that said first and second grating means are integrally formed into a grating assembly (2).
References Cited (Backward Citations)
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