Patent EP0273356A2 successfully refreshed from Google Patents.
EP0273356A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
An optical head
Assignee: NEC Corp
•
Filing: 1987-12-22
•
Granted: —
•
Expires: 2007-12-22
Abstract
Abstract In an optical head a conventional beam splitter or polarizing beam splitter is replaced by a grating lens (30). The grating lens (30) is composed of a plurality of regions (30A-30D) having different focal lengths and diffraction directions so that the light beam is divided into a predetermined number of light beams (34A-34D).
Inventors
- 👤 Yuzo C/O Nec Corporation Ono
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 16:49
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1381; G11B7/08; G11B7/09; G11B7/0901; G11B7/0903; G11B7/0908; G11B7/0916; G11B7/094; G11B7/1353; G11B7/1372; G11B7/1378
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
150 words
An optical head comprising, a light source for radiating light beam, a 1/4 wavelength plate for converting said light beam into circularly polarized light beam and for converting said circularly polarized light beam in the direction opposite to said light beam into linearly polarized beam, an object lens for focusing said circularly polarized light beam on a recording medium, a polarizing beam splitter for separating light beam which is reflected from said recording medium to be received through said 1/4 wavelength plate, a grating lens having a plurality of regions of different properties in regard to at least one of focal length and diffraction direction for diffracting light beam separated by said polarizing beam splitter, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens including zero-order diffraction light beam are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 2
Dependent Claim
150 words
An optical head comprising, a light source for radiating light beam, a 1/4 wavelength plate for converting said light beam into circularly polarized light beam and for converting said circularly polarized light beam in the direction opposite to said light beam into linearly polarized beam, an object lens for focusing said circularly polarized light beam on a recording medium, a polarizing beam splitter for separating light beam which is reflected from said recording medium to be received through said 1/4 wavelength plate, a grating lens having a plurality of regions of different properties in regard to at least one of focal length and diffraction direction for diffracting light beam separated by said polarizing beam splitter, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens including zero-order diffraction light beam are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 3
Dependent Claim
131 words
An optical head comprising, a light source for radiating light beam, an object lens for focusing said light beam on a recording medium, a beam splitter for separating light beam which is reflected from said recording medium, a grating lens having a plurality of regions of different properties in regard to at least one of a focal length and diffraction direction for diffracting light beam separated by said beam splitter, a polarizing means for converting zero-order diffraction light beam received from said grating lens into two linearly polarized light beams having orthogonally polarized planes, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens and said two linearly polarized light beams are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 4
Dependent Claim
131 words
An optical head comprising, a light source for radiating light beam, an object lens for focusing said light beam on a recording medium, a beam splitter for separating light beam which is reflected from said recording medium, a grating lens having a plurality of regions of different properties in regard to at least one of a focal length and diffraction direction for diffracting light beam separated by said beam splitter, a polarizing means for converting zero-order diffraction light beam received from said grating lens into two linearly polarized light beams having orthogonally polarized planes, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens and said two linearly polarized light beams are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 5
Dependent Claim
152 words
An optical head comprising, a light source for radiating light beam, an object lens for focusing said light beam on a recording medium, a beam splitter for separating light beam which is reflected from said recording medium, a 1/2 wavelength plate for rotating light beam separated by said beam splitter in its polarized plane by ninety degrees, a grating lens having a plurality of regions of different properties in regard to at least one of a focal length and diffraction direction for diffracting light beam supplied from said 1/2 wavelength plate, a polarizing means for converting zero-order diffraction light beam received from said grating lens into two linearly polarized light beams having orthogonally polarized planes, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens and said two linearly polarized light beams are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 6
Dependent Claim
152 words
An optical head comprising, a light source for radiating light beam, an object lens for focusing said light beam on a recording medium, a beam splitter for separating light beam which is reflected from said recording medium, a 1/2 wavelength plate for rotating light beam separated by said beam splitter in its polarized plane by ninety degrees, a grating lens having a plurality of regions of different properties in regard to at least one of a focal length and diffraction direction for diffracting light beam supplied from said 1/2 wavelength plate, a polarizing means for converting zero-order diffraction light beam received from said grating lens into two linearly polarized light beams having orthogonally polarized planes, and an optical detector having a plurality of light receiving surfaces, wherein light beams diffracted by said grating lens and said two linearly polarized light beams are detected by said plurality of light receiving surfaces corresponding thereto.
Claim 7
Dependent Claim
120 words
An optical head according to claims 1 to 3, wherein said grating lens is composed of first and second regions divided by a line intersecting the light axis of said object lens and being parallel to a tracking error direction of said recording medium, and of third and fourth regions provided symmetrically on said line, said first and second regions being different in their focal lengths and diffraction directions from each other, and said third and fourth regions being different in their focal lengths and diffraction directions from said first and second regions, and said plurality of light receiving surfaces of said optical detector are positioned dependent upon the arrangement of said first to fourth regions of said grating lens.
Claim 8
Dependent Claim
122 words
An optical head according to claims 1 to 3, wherein said grating lens is composed of first and second regions divided by a line intersecting the light axis of said object lens and being parallel to a track of said recording medium, and of third and fourth regions provided symmetrically on the both sides of said line, said first and second regions being different in their focal lengths and diffraction directions from each other, and said third and fourth regions being different in their focal lengths and diffraction directions from said first and second regions, and said plurality of light receiving surfaces of said optical detector are positioned dependent upon the arrangement of said first to fourth regions of said grating lens.
Claim 9
Dependent Claim
109 words
An optical head according to claim 1 to 3, wherein said grating lens is composed of first to fourth regions divided by two lines each being intersected in the center thereof and being not parallel and perpendicular to a track of said recording medium, said first and second regions being different in their focal lengths and diffraction directions from each other, and said third and fourth regions being different in their focal lengths and diffraction directions from said first and second regions, and said plurality of light receiving surfaces of said optical detector are positioned dependent upon the arrangement of said first to fourth regions of said grating lens.
Claim 10
Dependent Claim
75 words
An optical head according to claim 3, wherein the ratio of a wavelength of said light beam in regard to a pitch of gratings of said grating lens is equal to or more than 1.5 when the ratio of a depth of said grating in regard to said pitch is 0.5, and said grating lens is arranged such that a polarization of said light beam is of p-polarization on the surface of said grating lens.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.