US3723801A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Measuring the beam landing characteristic of a shadow-mask cathode-ray tube
Assignee: US Philips Corp
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Filing: 1970-07-16
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Granted: 1973-03-27
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Expires: 1990-07-16
Abstract
Abstract A method of adjusting the electron beam landing in a color display tube on the screen of which phosphor dots are provided which are impinged upon by the electron beams so that they luminesce with different colors. One electron beam is activated while the picture to be displayed is a white raster. Alternating current and direct current fields are adjusted in such a manner that the spots of the electron beams are arranged symmetrically relative to the phosphor dots, which may be found with the aid of a detector arrangement, for example, a photomultiplier which is exclusively sensitive to the color corresponding to the active electron beam. The landing characteristic may be measured and the color purity may be adjusted.
Inventors
- 👤 J Oxenham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:25
CPC Classifications
H; H04; H04N; H04N17/00; H04N17/04
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
149 words
A method of adjusting the electron beam landing point of color display tube having at least two electron beams and groups luminescent dots of differing colors on a screen, said method comprising scanning one of said beams across at least a portion of said screen, periodically displacing the beam landing point between two points about at least one of said dots having a distance therebetween of the same order as the larger of the dot diameter and the electron beam spot diameter, whereby said two points defining a line extending in a first direction, displacing said beam in said first direction by generating a steady field, detecting the light output only from dots having the same color as said one dot, and causing the light emitted by said dot when said beam is at said two points to be substantially equal by adjusting the magnitude of said steady field.
Claim 2
Independent Claim
149 words
A method of adjusting the electron beam landing point of color display tube having at least two electron beams and groups luminescent dots of differing colors on a screen, said method comprising scanning one of said beams across at least a portion of said screen, periodically displacing the beam landing point between two points about at least one of said dots having a distance therebetween of the same order as the larger of the dot diameter and the electron beam spot diameter, whereby said two points defining a line extending in a first direction, displacing said beam in said first direction by generating a steady field, detecting the light output only from dots having the same color as said one dot, and causing the light emitted by said dot when said beam is at said two points to be substantially equal by adjusting the magnitude of said steady field.
Claim 3
Dependent Claim
19 words
A method as claimed in claim 1 further comprising periodically and steadily displacing said point in a second direction.
Claim 4
Dependent Claim
18 words
A method as claimed in claim 2 wherein said second direction is substantially perpendicular to said first direction.
Claim 5
Dependent Claim
28 words
A method as claimed in claim 1 further comprising determining the value of the initial error in said landing point by measuring the value of said steady field.
Claim 6
Dependent Claim
17 words
A method as claimed in claim 1 further comprising adjusting the color purity by varying said fields.
Claim 7
Dependent Claim
27 words
A method as claimed in claim 1 wherein said first recited displacing step comprises geneRating a periodic magnetic field and said steady field comprises a magnetic field.
Claim 8
Dependent Claim
161 words
A circuit for adjusting the electron beam landing point of color display tube having at least two electron beams and groups of luminescent dots of differing color on a screen, said circuit comprising means for scanning one of said beams across at least a portion of said screen, magnetic field generating means for periodically displacing the beam landing point between two points about at least one of said dots and having a distance therebetween of the same order as the larger of the dot diameter and the electron beam spot diameter, whereby said two points define a line extending in a first direction, magnetic field generating means for displacing said beam in said first direction, means for detecting the light output only from dots having the same color as said one dot, and means for substantially equalizing the light emitted by said dot when said beam is at said two points including means for adjusting the magnitude of said steady field.
Claim 9
Dependent Claim
161 words
A circuit for adjusting the electron beam landing point of color display tube having at least two electron beams and groups of luminescent dots of differing color on a screen, said circuit comprising means for scanning one of said beams across at least a portion of said screen, magnetic field generating means for periodically displacing the beam landing point between two points about at least one of said dots and having a distance therebetween of the same order as the larger of the dot diameter and the electron beam spot diameter, whereby said two points define a line extending in a first direction, magnetic field generating means for displacing said beam in said first direction, means for detecting the light output only from dots having the same color as said one dot, and means for substantially equalizing the light emitted by said dot when said beam is at said two points including means for adjusting the magnitude of said steady field.
Claim 10
Dependent Claim
109 words
A circuit as claimed in claim 7 wherein each of said magnetic field generating means comprises at least one coil disposed adjacent said tube, direct and alternating current sources coupled to said coil, switching means coupled between said alternating sources and said coil; said detecting means comprising a photomultiplier, a switching means coupled to said photo-multiplier and synchronized with both of said generating means switching means, first and second differential amplifiers each having two input means coupled to said detecting means switching means, said amplifiers receiving said light corresponding to the deflection caused by each of said generating means respectively, and two storage means coupled to said amplifiers respectively.
Claim 11
Dependent Claim
41 words
A circuit as claimed in claim 8 wherein each of said switching means comprise electronic switches controlled by a switching signal having a frequency equal to or an even multiple of one fourth of the field deflection frequency and synchronized therewith.
Claim 12
Dependent Claim
19 words
A circuit as claimed in claim 8 wherein said coils are disposed adjacent the neck of said display tube.
Claim 13
Dependent Claim
21 words
A circuit as claimed in claim 8 wherein said coils are disposed adjacent said tube screen for adjusting the color purity.
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) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |