US5612942A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical head
Assignee: NEC Corp
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Filing: 1994-11-21
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Granted: 1997-03-18
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Expires: 2014-11-21
Abstract
Abstract A light radiated from a light source is focused to provide a light spot on an optical disc. A central portion of the radiated light is shielded, and a peripheral portion of the radiated light is modulated to have an intensity decreasing in an outer periphery direction, respectively, by a light intensity modulator. Consequently, a diameter of the light spot is reduced, and side-lobes are suppressed. In place of the light intensity modulator, a light source filter and a second filter are used. A secondary light source is formed by focusing the radiated light. At a point of the secondary light source, the light source filter having a central portion of 0% and a peripheral portion of 100%, respectively, in light transmission intensity is provided. On an output side of a collimator lens, the second filter having central portion of 100% and a peripheral portion of 0%, respectively, in light transmission intensity is provided.
Inventors
- 👤 Jun-ichi Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:51
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/125; G11B7/128; G11B7/135; G11B7/1381; G11B7/1372; G11B2007/13727
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
156 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; means for converting said first and second light beams to first and second electric signals; a light source filter for converting an intensity distribution of said radiated light beam to an intensity distribution of a disc having a circular aperture to provide an intensity distribution-converted light which is supplied to said collimator lens as said radiated light beam; and a second filter for converting an intensity distribution of said intensity distribution of said distribution-converted light dependently on said intensity distribution-converted light, said second filter being positioned at an output stage of said collimator.
Claim 2
Dependent Claim
156 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; means for converting said first and second light beams to first and second electric signals; a light source filter for converting an intensity distribution of said radiated light beam to an intensity distribution of a disc having a circular aperture to provide an intensity distribution-converted light which is supplied to said collimator lens as said radiated light beam; and a second filter for converting an intensity distribution of said intensity distribution of said distribution-converted light dependently on said intensity distribution-converted light, said second filter being positioned at an output stage of said collimator.
Claim 3
Dependent Claim
31 words
An optical head, according to claim 1, wherein: said light source is a semiconductor laser provided on a semiconductor chip; and said light source filter is provided on said semiconductor chip.
Claim 4
Dependent Claim
35 words
An optical head, according to claim 1, wherein: said light source filter is positioned between a condenser lens and said collimator lens, said condenser lens being provided on an output side of said light source.
Claim 5
Dependent Claim
64 words
An optical head, according to claim 1, wherein: said light source filter provides an intensity distribution O' (u,v) for suppressing a change of side-lobes of an image, and has a property in which an image plane intensity distribution I' (x,y) of light including information reproduced from said optical disc is represented by the equation, I'(x,y)=∫∫O'(u,v)·D'(x-u, y-v)du·dv where D' (x-u, y-v) is an impulse response.
Claim 6
Dependent Claim
113 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; means for converting said first and second light beams to first and second electric signals; and a light intensity modulator for reducing a diameter of said light spot and suppressing side-lobes generated around said light spot, said light intensity modulator being positioned between said collimator lens and said objective lens.
Claim 7
Dependent Claim
113 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; means for converting said first and second light beams to first and second electric signals; and a light intensity modulator for reducing a diameter of said light spot and suppressing side-lobes generated around said light spot, said light intensity modulator being positioned between said collimator lens and said objective lens.
Claim 8
Dependent Claim
38 words
An optical head, according to claim 5, wherein: said light intensity modulator, comprises: a central portion having a light transmission intensity of 0%; and a peripheral portion having a light transmission intensity decreasing in an outer peripheral direction.
Claim 9
Dependent Claim
37 words
An optical head, according to claim 5, wherein: said light intensity modulator, comprises: a central portion having a phase shift of π; and a peripheral portion having a light transmission intensity decreasing in an outer peripheral direction.
Claim 10
Dependent Claim
157 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; photoelectric converters to convert said first and second light beams to first and second electric signals; a light source filter for converting an intensity distribution of said radiated light beam to an intensity distribution of a disc having a circular aperture to provide an intensity distribution-converted light which is supplied to said collimator lens as said radiated light beam; and a second filter for converting an intensity distribution of said intensity distribution of said distribution-converted light dependently on said intensity distribution-converted light, said second filter being positioned at an output stage of said collimator.
Claim 11
Dependent Claim
157 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; photoelectric converters to convert said first and second light beams to first and second electric signals; a light source filter for converting an intensity distribution of said radiated light beam to an intensity distribution of a disc having a circular aperture to provide an intensity distribution-converted light which is supplied to said collimator lens as said radiated light beam; and a second filter for converting an intensity distribution of said intensity distribution of said distribution-converted light dependently on said intensity distribution-converted light, said second filter being positioned at an output stage of said collimator.
Claim 12
Dependent Claim
114 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; photoelectric converters to convert said first and second light beams to first and second electric signals; and a light intensity modulator for reducing a diameter of said light spot and suppressing side-lobes generated around said light spot, said light intensity modulator being positioned between said collimator lens and said objective lens.
Claim 13
Dependent Claim
114 words
An optical head, comprising: a light source for providing a radiated light beam; a collimator lens for collimating said radiated light beam to provide a collimated light; an objective lens for focusing said collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from said optical disc to first and second light beams; photoelectric converters to convert said first and second light beams to first and second electric signals; and a light intensity modulator for reducing a diameter of said light spot and suppressing side-lobes generated around said light spot, said light intensity modulator being positioned between said collimator lens and said objective lens.
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