US5072437A
Expired / Lapsed
US
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Optical information reproducing apparatus
Assignee: Pioneer Corp
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Filing: 1990-02-23
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Granted: 1991-12-10
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Expires: 2010-02-23
Abstract
Abstract To prevent a drop in signal level at high spatial frequencies, an optical information reproducing apparatus retrieves the primary output of light reflected from the surface of a recording medium. In the different embodiments of the invention, either a shield plate with a pinhole in the path of the light is provided, or a photodetector having a plurality of light-receiving elements is provided, a selection circuit being connected to the elements and selecting the highest output thereof.
Inventors
- 👤 Kiyofumi Chikuma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:37
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/125; B; B82; B82Y; B82Y10/00; G11B7/13; G11B7/135; G11B7/1381
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
138 words
An optical information reproducing apparatus comprising: a photodetector; a light source; light wavelength converting means by which the light emitted from said light source is converted to light having one half the wavelength of said light from said light source; a first optical unit for converging light from said light wavelength converting means at a point on the recording surface of a recording medium, a second optical unit for directing light reflected from said recording medium to said photodetector; and a shield plate disposed between said first optical unit and said photodetector, wherein a small hole is provided in said shield plate in a path of light toward said photodetector in the vicinity of a point conjugative with the point at which the light from said light source is converged on the recording surface of said recording medium.
Claim 2
Dependent Claim
138 words
An optical information reproducing apparatus comprising: a photodetector; a light source; light wavelength converting means by which the light emitted from said light source is converted to light having one half the wavelength of said light from said light source; a first optical unit for converging light from said light wavelength converting means at a point on the recording surface of a recording medium, a second optical unit for directing light reflected from said recording medium to said photodetector; and a shield plate disposed between said first optical unit and said photodetector, wherein a small hole is provided in said shield plate in a path of light toward said photodetector in the vicinity of a point conjugative with the point at which the light from said light source is converged on the recording surface of said recording medium.
Claim 3
Dependent Claim
43 words
An optical information reproducing apparatus according to claim 1 wherein said light wavelength converting means is a second harmonics generating (SHG) element of a fiber type that is fabricated by crystallizing a nonlinear optical medium confined in the core of an optical fiber.
Claim 4
Dependent Claim
33 words
An optical information reproducing apparatus according to claim 8, wherein said first optical unit comprises an objective lens having a smaller light transmittance in a central portion thereof than in the remaining area.
Claim 5
Dependent Claim
26 words
An optical information reproducing apparatus according to claim 1, further comprising a collimation lens disposed between said light wavelength converting means and said second optical unit.
Claim 6
Dependent Claim
21 words
An optical information reproducing apparatus according to claim 4, wherein said collimation lens comprises a conical prism having a conical surface.
Claim 7
Dependent Claim
24 words
An optical information reproducing apparatus according to claim 1, further comprising a condenser lens disposed between said second optical unit and said shield plate.
Claim 8
Dependent Claim
18 words
An optical information reproducing apparatus according to claim 1, wherein said second optical unit comprises a beam splitter.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-12-09 | 1995-06-10 | 1995-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-12-09 | 1999-06-10 | 1999-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-12-09 | 2003-06-10 | 2003-12-10 | $7700.00 | Window Closed / Lapsed |