Patent US6277139B1 successfully refreshed from Google Patents.
US4751566A
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US
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Method and device for gamma correction in multichrome cathode ray tubes
Assignee: Societe Francaise dEquipements pour la Navigation Aerienne SFENA SA
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Filing: 1987-03-26
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Granted: 1988-06-14
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Expires: 2007-03-26
Abstract
Abstract A gamma correction method and device are provided for multichrome cathode y tubes, including, for each of the n-1 electron guns of the tube, a correction circuit adapted for raising the cathode modulation of this gun to a power γref/γ i in which the term γ ref is the gamma exponent of the nth gun which is taken as reference and the term γ i is the gamma exponent of the gun considered. With this device the chromaticity of the colors displayed on the screen are conserved throughout the whole contrast dynamics of the tube.
Inventors
- 👤 Alain Pilot
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 17:44
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/68; H04N9/69
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
178 words
A gamma correction method for multichrome cathode ray tubes equipped with a contrast control circuit acting simultaneously on the cathode modulation signals of the electron guns of the tube, comprising: taking as reference the transfer function L ref =K ref (M ref ).sup.γ.sbsp.ref relative to one of the guns of the tube, L ref being the luminance generated by the reference gun, M ref being the modulation applied to the cathode of the reference gun, K ref being representative of a constant and the term γ ref representing the gamma exponent of the reference gun, and applying to the other guns a differential correction causing the cathode modulation M i of these other guns to pass to a value M i γ ref /γ i in which the exponent γ i is the gamma exponent of the gun considered so as to make the transfer functions of said other guns proportional to that of the gun taken as reference, and so that consequently the ratio of the luminances remains constant whatever the contrast control level of the tube.
Claim 2
Dependent Claim
178 words
A gamma correction method for multichrome cathode ray tubes equipped with a contrast control circuit acting simultaneously on the cathode modulation signals of the electron guns of the tube, comprising: taking as reference the transfer function L ref =K ref (M ref ).sup.γ.sbsp.ref relative to one of the guns of the tube, L ref being the luminance generated by the reference gun, M ref being the modulation applied to the cathode of the reference gun, K ref being representative of a constant and the term γ ref representing the gamma exponent of the reference gun, and applying to the other guns a differential correction causing the cathode modulation M i of these other guns to pass to a value M i γ ref /γ i in which the exponent γ i is the gamma exponent of the gun considered so as to make the transfer functions of said other guns proportional to that of the gun taken as reference, and so that consequently the ratio of the luminances remains constant whatever the contrast control level of the tube.
Claim 3
Dependent Claim
43 words
The method as claimed in claim 1, wherein said correction is carried out by creating, with straight line segments, a mathematical model of a correction curve defined by a relation y=M i γ ref /γ i y representing the amplitude of the correction.
Claim 4
Dependent Claim
28 words
The method as claimed in claim 1, which comprises the step of applying said correction in the video channel, to the cathode modulation signals of the electron guns.
Claim 5
Dependent Claim
19 words
The method as claimed in claim 1, which comprises the step of applying said correction to the contrast control.
Claim 6
Dependent Claim
89 words
The method as claimed in claim 1, wherein said correction includes for each of the electron guns considered the steps of: determining the curve of correction to be made to the cathode modulation signal of this gun, creating a mathematical model of this correction curve by means of straight line segments which each correspond to a range of variation of the modulation signal, amplifying the modulation signal in each of said ranges with a gain depending on the slope of the corresponding straight line segment of the model curve.
Claim 7
Independent Claim
83 words
A device for effecting a gamma correction for a multichrome cathode ray tube provided with n electrode guns, said device comprising for each of the n-1 electron guns of the tube a correction circuit adapted for raising the cathode modulation of this gun to a power γ ref /γ i , in which the term γ ref is the gamma exponent of the nth gun which is taken as reference and the term γ i is the gamma exponent of the gun considered.
Claim 8
Independent Claim
83 words
A device for effecting a gamma correction for a multichrome cathode ray tube provided with n electrode guns, said device comprising for each of the n-1 electron guns of the tube a correction circuit adapted for raising the cathode modulation of this gun to a power γ ref /γ i , in which the term γ ref is the gamma exponent of the nth gun which is taken as reference and the term γ i is the gamma exponent of the gun considered.
Claim 9
Dependent Claim
31 words
The device as claimed in claim 6, wherein said correction circuits are disposed in the red and green video circuits connecting the contrast variation circuits to the n-1 corresponding electron guns.
Claim 10
Dependent Claim
31 words
The device as claimed in claim 6 wherein said correction circuits are disposed in the circuits connecting the contrast adjustment device to the contrast variation circuits assigned to said n-1 guns.
Claim 11
Dependent Claim
16 words
The device as claimed in claim 6, wherein said correction circuit consists of slope switching circuit.
Claim 12
Dependent Claim
29 words
The device as claimed in claim 6, wherein said correction circuit includes an amplifier-summator circuit receiving the signal to be corrected directly and through at least one threshold device.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-14 | 1991-12-14 | 1992-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-14 | 1995-12-14 | 1996-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-14 | 1999-12-14 | 2000-06-14 | $7700.00 | Window Closed / Lapsed |