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US4991937A
Expired / Lapsed
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Birefringence diffraction grating type polarizer
Assignee: NEC Corp
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Filing: 1989-06-27
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Granted: 1991-02-12
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Expires: 2009-06-27
Abstract
Abstract In a birefringence diffraction grating type polarizer, periodical proton ion-exchanged regions are provided on the principal plane of an optically anisotropic crystal substrate to provide an optical diffraction grating, and a dielectric layer is provided on each of the periodical proton ion-exchanged regions. The refractive index of the dielectric layer is proximate or equal to that of the crystal substrate, and the whole surface of the optical diffraction grating is covered by an anti-reflection layer of a single material having a uniform thickness.
Inventors
- 👤 Yutaka Urino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:22
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/18; G02B5/1833; G02B5/30; G02B5/3083
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
73 words
A birefringence diffraction grating type polarizer: comprising, an optically anisotropic sheet crystal substrate having periodical ion-exchanged regions to provide a birefringence diffraction grating which functions as a polarizer; dielectric layers each provided over each of said ion-exchange regions, and having a refractive index proximate or equal to that of said crystal substrate; and an anti-reflection layer of a uniform thickness provided over the whole surface of said crystal substrate and said dielectric layers.
Claim 2
Dependent Claim
73 words
A birefringence diffraction grating type polarizer: comprising, an optically anisotropic sheet crystal substrate having periodical ion-exchanged regions to provide a birefringence diffraction grating which functions as a polarizer; dielectric layers each provided over each of said ion-exchange regions, and having a refractive index proximate or equal to that of said crystal substrate; and an anti-reflection layer of a uniform thickness provided over the whole surface of said crystal substrate and said dielectric layers.
Claim 3
Dependent Claim
50 words
A birefringence diffraction grating type polarizer as defined in claim 1, wherein said dielectric layers are of a substance selected from lithium niobate, niobium pentoxide, zirconium oxide, zinc sulphide (ZnS), titanium dioxide (TiO 2 ), cerium dioxide (CeO 2 ), tantalum pentoxide (Ta 2 O 5 ) and tellurium oxide.
Claim 4
Dependent Claim
39 words
A birefringence diffraction grating type polarizer as defined in claim 1, wherein said anti-reflection layer is of a material of a refractive index nearly equal to the square root value of the refractive index of said sheet crystal substrate.
Claim 5
Dependent Claim
42 words
A birefringence diffraction grating type polarizer as defined in claim 3, wherein said anti-reflection layer is of a thickness determined in the calculation in which a light wavelength is divided by a value four times the refractive index of said anti-reflection layer.
Claim 6
Dependent Claim
46 words
A birefringence diffraction grating type polarizer as defined in claim 3, wherein said anti-reflection layer is of a material selected from silicon dioxide, calcium fluoride (CaF 2 ), aluminum fluoride (AlF 3 ), lanthanum fluoride (LaF 3 ), strontium fluoride (SrF 2 ) and magnesium fluoride.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-02-11 | 1994-08-13 | 1995-02-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-11 | 1998-08-13 | 1999-02-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-11 | 2002-08-13 | 2003-02-12 | $7700.00 | Window Closed / Lapsed |