US3706905A
Expired / Lapsed
US
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Deflection compensation system
Assignee: Computer Terminal Corp
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Filing: 1970-05-14
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Granted: 1972-12-19
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Expires: 1990-05-14
Abstract
Abstract A system for correcting distortion in the deflection of the beam in a cathode ray tube used to display lines of alphanumeric characters as in a computer terminal unit. Characters are generated one at a time rather than in a TV type raster. This requires a horizontal deflection signal of sawtooth form to create lines, and two separate vertical deflection systems, a major vertical deflection to generate the desired number of lines on the screen, and a minor vertical deflection of much higher frequency to write the characters on a given line. Correction is applied to the horizontal deflection signal and to the minor vertical deflection signal to compensate for the distortion caused by using a short, flat screened tube. The correction signal for both horizontal and vertical may be derived from a single source.
Inventors
- 👤 Jack F Alexander
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 20:11
CPC Classifications
H; H03; H03K; H03K6/00; H03K6/04; G; G09; G09G; G09G1/00; G09G1/04
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
133 words
A system for correcting deflection of a beam in a cathode ray tube used to display lines of alphanumeric characters or the like, comprising horizontal deflection means for producing a repetitive horizontal sweep signal, first vertical deflection means for repetitively producing a first vertical deflection signal in the form of a stepped waveform providing a sequence of discrete levels corresponding to lines for writing of characters, second vertical deflection means for producing a second vertical deflection signal at a rate much higher than said period of persistance of said discrete levels produced by first vertical deflection means, and at an amplitude much smaller than that produced by the first vertical deflection means, and means for impressing upon said second vertical deflection signal an amplitude correction signal which varies during a horizontal sweep period.
Claim 2
Independent Claim
133 words
A system for correcting deflection of a beam in a cathode ray tube used to display lines of alphanumeric characters or the like, comprising horizontal deflection means for producing a repetitive horizontal sweep signal, first vertical deflection means for repetitively producing a first vertical deflection signal in the form of a stepped waveform providing a sequence of discrete levels corresponding to lines for writing of characters, second vertical deflection means for producing a second vertical deflection signal at a rate much higher than said period of persistance of said discrete levels produced by first vertical deflection means, and at an amplitude much smaller than that produced by the first vertical deflection means, and means for impressing upon said second vertical deflection signal an amplitude correction signal which varies during a horizontal sweep period.
Claim 3
Dependent Claim
49 words
A system according to claim 1 wherein means are provided for generating said amplitude correction signal such that it has a waveform which is at or near zero in the middle of a horizontal sweep period and is a maximum at the beginning and end of each such period.
Claim 4
Dependent Claim
30 words
A system according to claim 1 wherein the means for generating said amplitude correction signal receives as an input a signal derived from the output of the horizontal deflection means.
Claim 5
Dependent Claim
24 words
A system according to claim 1 wherein the horizontal deflection means includes a constant current source charging a capacitor to provide a sweep signal.
Claim 6
Dependent Claim
31 words
A system according to claim 1 wherein the repetition rate of the horizontal sweep signal corresponds to the period of persistance of said discrete levels of the first vertical deflection signal.
Claim 7
Dependent Claim
27 words
A system according to claim 1 wherein means are provided for imposing upon said horizontal sweep signal an amplitude correction which varies during the horizontal sweep period.
Claim 8
Dependent Claim
33 words
A system according to claim 6 wherein the amplitude correction signal for the second vertical deflection signal and the amplitude correction for the horizontal sweep signal are both derived from the same source.
Claim 9
Dependent Claim
44 words
A system according to claim 7 wherein said source includes means for generating a correction signal having a waveform which is a minimum in the middle of a horizontal sweep period and is a maximum at the beginning and end of each such period.
Claim 10
Dependent Claim
29 words
A system according to claim 8 wherein said means for generating said correction signal receives as an input a signal derived from the output of the horizontal deflection means.
Claim 11
Independent Claim
161 words
A system for correcting deflection of a beam in a cathode ray tube and to display lines of alphanumeric characters or the like, comprising horizontal deflection means for producing a repetitive horizontal sweep signal, including a constant current source charging a capacitor to provide such sweep signal, first vertical deflection means for producing a repetitive vertical deflection signal in the form of a stepped waveform providing a sequence of discrete levels corresponding to lines for writing of characters, the repetition rate of the horizontal sweep signal corresponding to the period of persistence of said discrete levels, second vertical deflection means for producing a vertical deflection signal at a rate much higher than said period of persistance of said discrete levels produced by first vertical deflection means, and at an amplitude much smaller than that produced by the first vertical deflection means, and means for impressing upon said horizontal deflection sweep signal an amplitude correction signal which varies during the sweep period.
Claim 12
Independent Claim
161 words
A system for correcting deflection of a beam in a cathode ray tube and to display lines of alphanumeric characters or the like, comprising horizontal deflection means for producing a repetitive horizontal sweep signal, including a constant current source charging a capacitor to provide such sweep signal, first vertical deflection means for producing a repetitive vertical deflection signal in the form of a stepped waveform providing a sequence of discrete levels corresponding to lines for writing of characters, the repetition rate of the horizontal sweep signal corresponding to the period of persistence of said discrete levels, second vertical deflection means for producing a vertical deflection signal at a rate much higher than said period of persistance of said discrete levels produced by first vertical deflection means, and at an amplitude much smaller than that produced by the first vertical deflection means, and means for impressing upon said horizontal deflection sweep signal an amplitude correction signal which varies during the sweep period.
Claim 13
Dependent Claim
57 words
A system according to claim 10 wherein means are provided for generating a correction signal having a waveform which is at or near zero in the middle of a horizontal sweep period and is at a maximum at the beginning and end of each such period, and said correction signal is used to generate said amplitude correction.
Claim 14
Dependent Claim
26 words
A system according to claim 11 wherein the correction signal is coupled to said constant current source to alter the rate of charging of the capacitor.
Claim 15
Dependent Claim
29 words
A system according to claim 12 wherein the means for generating a correction signal is controlled by a feedback signal derived from the output of the horizontal deflection means.
Claim 16
Dependent Claim
41 words
A system according to claim 13 wherein the constant current source includes a transistor having a fixed base bias and an emitter bias which is a fixed level altered by the correction signal, with the capacitor being in the collector circuit.
Claim 17
Dependent Claim
46 words
A system aCcording to claim 14 wherein the means for generating a correction signal includes a pair of transistors connected as an opposing pair with a single output, the input to the transistors being said feedback signal, the output of the transistors being said correction signal.
Claim 18
Independent Claim
108 words
A method of correcting deflection of a beam in a cathode ray tube used to display lines of alphanumeric characters or the like, comprising the steps of: repetitively charging a capacitor from a constant current source to generate a horizontal deflection sweep signal, generating a correction signal in time synchronization with said horizontal deflection sweep signal, the correction signal being shaped to exhibit a waveform which is at a minimum in the middle of a horizontal sweep period and is a maximum at the beginning and end of such sweep period, and controlling the magnitude of output of the constant current source in accordance with said correction signal.
Claim 19
Independent Claim
108 words
A method of correcting deflection of a beam in a cathode ray tube used to display lines of alphanumeric characters or the like, comprising the steps of: repetitively charging a capacitor from a constant current source to generate a horizontal deflection sweep signal, generating a correction signal in time synchronization with said horizontal deflection sweep signal, the correction signal being shaped to exhibit a waveform which is at a minimum in the middle of a horizontal sweep period and is a maximum at the beginning and end of such sweep period, and controlling the magnitude of output of the constant current source in accordance with said correction signal.
Claim 20
Dependent Claim
50 words
A method according to claim 16 including the steps of generating a first vertical deflection signal to create lines and a second vertical deflection signal to generate characters on the face of the tube, and controlling the magnitude of the second vertical deflection signal in accordance with said correction signal.
Claim 21
Dependent Claim
30 words
A method according to claim 17 wherein the correction signal is generated by using as an input a signal related to current in the horizontal deflection yoke of the tube.
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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) | 1975-12-19 | 1976-06-19 | 1976-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-19 | 1980-06-19 | 1980-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-19 | 1984-06-19 | 1984-12-19 | $7700.00 | Window Closed / Lapsed |