US4859902A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of changing the chromaticity of a cathodoluminescent phosphor, colour cathode ray tube incorporating the phosphor, and projection television using same
Assignee: US Philips Corp
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Filing: 1987-09-30
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Granted: 1989-08-22
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Expires: 2007-09-30
Abstract
Abstract Phosphors used in colour cathode ray tubes, particularly but not exclusively projection television tubes, have colour point standards or chromaticities modified to conform to European Broadcasting Union (EBU) standards by disposing an interference filter in the light-path from the phosphor, for example, between the phosphor and the faceplate, which has a peak gain greater than unity over a selected part of the frequency spectrum. As a result, an efficient broadband phosphor can be employed to obtain the desired chromaticity and thereby increase the white-D luminance of projection television systems.
Inventors
- 👤 Dagobert M. de Leeuw
- 👤 Dirk B. M. Klaassen
- 👤 Cornelis A. H. A. Mutsaers
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 17:12
CPC Classifications
H; H01; H01J; H01J29/00; H01J29/02; H01J29/10; H01J29/18; H01J29/28; H01J29/185
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
110 words
A method of changing the chromaticity without losing the white D-capability of the emission of a cathodoluminescent phosphor having a broadband emission spectrum, said emission spectrum having a chromaticity outside an acceptable range for color television, the method comprising disposing an interference filter in the light path from the phosphor, the gain of said interference filter being larger than unity over a narrow band around a wavelength of maximum gain, of order unity for wavelengths smaller than the narrow band and decreasing to zero for wavelengths larger than the narrow band, said narrow band being positioned so that the filtered broad band emission has a chromaticity acceptable for color television.
Claim 2
Independent Claim
110 words
A method of changing the chromaticity without losing the white D-capability of the emission of a cathodoluminescent phosphor having a broadband emission spectrum, said emission spectrum having a chromaticity outside an acceptable range for color television, the method comprising disposing an interference filter in the light path from the phosphor, the gain of said interference filter being larger than unity over a narrow band around a wavelength of maximum gain, of order unity for wavelengths smaller than the narrow band and decreasing to zero for wavelengths larger than the narrow band, said narrow band being positioned so that the filtered broad band emission has a chromaticity acceptable for color television.
Claim 3
Dependent Claim
18 words
A method as claimed in claim 1, characterized in that the cathodoluminescent phosphor is a blue emitting phosphor.
Claim 4
Dependent Claim
114 words
A cathode ray tube comprising an envelope including an optically transparent faceplate, a cathodoluminescent phosphor carried by the faceplate having a broadband emission spectrum around a wavelength of maximum emission, said emission spectrum having a chromaticity outside an acceptable range for color television, and an interference filter mounted in the lightpath from the phosphor, the gain of said interference filter being larger than unity over a narrow band around a wavelength of maximum gain, of order unity for wavelengths smaller than the narrow band and decreasing to zero for wavelengths larger than the narrow band, said narrow band being positioned so that the filtered broad band emission has a chromaticity acceptable for color television.
Claim 5
Dependent Claim
114 words
A cathode ray tube comprising an envelope including an optically transparent faceplate, a cathodoluminescent phosphor carried by the faceplate having a broadband emission spectrum around a wavelength of maximum emission, said emission spectrum having a chromaticity outside an acceptable range for color television, and an interference filter mounted in the lightpath from the phosphor, the gain of said interference filter being larger than unity over a narrow band around a wavelength of maximum gain, of order unity for wavelengths smaller than the narrow band and decreasing to zero for wavelengths larger than the narrow band, said narrow band being positioned so that the filtered broad band emission has a chromaticity acceptable for color television.
Claim 6
Dependent Claim
20 words
A cathode ray tube as claimed in claim 3, characterized in that the cathodoluminescent phosphor is a blue emitting phosphor.
Claim 7
Dependent Claim
29 words
A cathode ray tube as claimed in claim 4, characterized in that the phosphor is Y 2 SiO 5 :Ce and the wavelength of maximum gain is 500 nm.
Claim 8
Dependent Claim
27 words
A cathode ray tube as claimed in claim 4, characterized in that the phosphor is (Ca,Mg)SiO 3 :Ti and the wavelength of maximum gain is 485 nm.
Claim 9
Dependent Claim
29 words
A cathode ray tube as claimed in claim 4, characterized in that the phosphor is SrGa 2 S 4 :Ce and the wavelength of maximum gain is 480 nm.
Claim 10
Dependent Claim
74 words
A cathode ray tube as claimed in claim 3, characterized in that the interference filter comprises between 14 and 30 layers formed by alternating high and low refractive index layers, each individual layer having an optical thickness lying between 0.2λ f and 0.3λ f with an average optical thickness of 0.25λ f , where λ f is equal to p times the wavelengths of maximum gain, p being a number between 1.2 and 1.33.
References Cited (Backward Citations)
FR737223A
Cited
US3742277A
Cited
DE2920830A1
Cited
EP0170320A1
Cited
US4634926A
Cited
US4647812A
Cited
GB2176048A
Cited
US4683398A
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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) | 1992-08-21 | 1993-02-20 | 1993-08-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-21 | 1997-02-20 | 1997-08-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-21 | 2001-02-20 | 2001-08-22 | $7700.00 | Window Closed / Lapsed |