EP0612068A2
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EP
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Optical head device and birefringent diffraction grating polarizer and polarizing hologram element used therein
Assignee: NEC Corp
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Filing: 1994-02-16
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Granted: —
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Expires: 2014-02-16
Abstract
Abstract An optical head device uses a birefringent diffraction grating polarizer configured in a reflection type. The device includes a polarizing hologram element (216) which reflects the light from a light source (210) to a converging lens system and diffracts the polarized light returning from a recording medium. A total reflection film (203) is formed on a surface of a diffraction grating which is provided periodically by an ion exchange region and a dielectric film on a surface of a crystal plate (200) having optically anisotropic characteristics. A polarizing beam splitter film (218) formed on a surface of the polarizing hologram element has reflectivity and transmissivity having dependency on the polarization of the incident light. In another form, a polarizing hologram element includes a polarizing hologram which has diffractive efficiency having dependency on polarization of incident light and a polarizing beam splitter film (218) which has reflectivity and transmissivity having dependency on the polarization of the incident light. The diffracted light is received by multi-split photodetectors. The arrangements enable to make the optical head device compact, light in weight and low cost.
Inventors
- 👤 Yuzo C/O Nec Corporation Ono
- 👤 Akitomo C/O Nec Corporation Oba
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 08:50
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1353; G02; G02B; G02B27/00; G02B27/28; G02B5/00; G02B5/18; G02B5/1833; G02B5/32; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10541; G11B11/10543; G11B7/123; G11B7/13; G11B7/131
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
56 words
A birefringent diffraction grating polarizer comprising: a crystal plate (200) having optically anisotropic characteristics; an ion exchange region (201) and a dielectric film (202) which constitute a diffraction grating and which are formed periodically on a main surface of said crystal plate; and a total reflection film (203) Formed on a surface of said diffraction grating.
Claim 2
Dependent Claim
34 words
A birefringent diffraction grating polarizer according to claim 1, further comprising a polarizing beam splitter layer (218) on a partial region of a surface opposite to said main surface of said crystal plate (200).
Claim 3
Dependent Claim
34 words
A birefringent diffraction grating polarizer according to claim 1, further comprising a polarizing beam splitter layer (218) on an entire region of a surface opposite to said main surface of said crystal plate (200).
Claim 4
Dependent Claim
23 words
A polarizer according to claim 1, 2, or 3, in which said dielectric film (202) is arranged on said ion exchange region (201).
Claim 5
Dependent Claim
34 words
A polarizer according to any one of claims 1 to 4, in which said ion exchange region (201) and said dielectric film (202) are alternately arranged along the main surface of said crystal plate,
Claim 6
Dependent Claim
22 words
A polarizer according to any one of claims 1 to 5, in which said total reflection film (203) is a metal film.
Claim 7
Dependent Claim
121 words
An optical head device comprising: a light source (210); a converging means (211,212) for converging light beams emitted from said light source on a recording medium (214); a polarizing hologram element (216) obliquely disposed between said light source and said converging means, for reflecting a part of the light beams emitted from said light source to be incident on said converging means and for spatially dividing and diffracting a part of reflected light coming from said recording medium via said converging means, said polarizing hologram element having on its main surface a plurality of divided hologram regions; and a photodetector means (260) having a plurality of light receiving sections each of which receives the diffracted light from said polarizing hologram element.
Claim 8
Dependent Claim
30 words
An optical head device according to claim 7, in which said polarizing hologram element (216) has a polarizing beam splitter film (218) on a surface opposite to said main surface.
Claim 9
Dependent Claim
23 words
An optical head device according to claim 8, in which said converging means includes a collimating lens (211) and a convergent lens (212).
Claim 10
Dependent Claim
145 words
An optical head device comprising: a light source (210;221); a converging lens system (211,212) for converging light beams emitted from said light source on a recording medium (214); a quarter-wavelength plate (213) for causing polarized light returning from said recording medium to be orthogonal with respect to polarized light emitted from said light source; a hologram element (216) for reflecting the light from said light source to said converging lens system and for reflectively diffracting the light returning from said recording medium; and a photodetector means (230,231;223) for receiving said diffracted light, wherein said hologram element comprises a crystal plate (200) having optically anisotropic characteristics, an ion exchange region (201) and a dielectric film (202) constituting a diffraction grating and being formed periodically on a main surface of said crystal plate, and a total reflection film (203) formed on a surface of said diffraction grating.
Claim 11
Dependent Claim
26 words
An optical head device according to claim 10, in which said light source (221) and said photodetector means (223) are accommodated in an Integrated module (230).
Claim 12
Dependent Claim
34 words
An optical head device according to claim 10 or 11, in which said converging lens system includes a collimating lens (211) and an objective lens (212) with said quarter-wavelength plate (213) being arranged therebetween.
Claim 13
Dependent Claim
142 words
An optical head device comprising: a light source (210:241); a converging lens system (211,212) for converging light beams emitted from said light source on a recording medium (214): a hologram element (216) for reflecting the light from said light source to said converging lens system and for reflectively diffracting the light returning from said recording medium; and a photodetector means (232;243) for receiving said diffracted light, wherein said hologram element comprises a crystal plate (200) having optically anisotropic characteristics, an ion exchange region (201) and a dielectric film (202) constituting a diffraction grating and being formed periodically on a main surface of said crystal plate, a total reflection film (203) formed on a surface of said diffraction grating, and a polarizing beam splitter layer (218) formed on a partial region of a surface opposite to said main surface of said crystal plate.
Claim 14
Dependent Claim
26 words
An optical head device according to claim 13, in which said light source (241) and said photodetector means (243) are accommodated in an integrated module (240).
Claim 15
Dependent Claim
26 words
An optical head device according to claim 13 or 14, in which said converging lens system includes a collimating lens (211) and an objective lens (212).
References Cited (Backward Citations)
No citation records indexed.
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