EP0180450A2
Expired / Lapsed
EP
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Television display apparatus having character generator with non-line-locked clock
Assignee: RCA Licensing Corp
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Filing: 1985-10-29
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Granted: —
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Expires: 2005-10-29
Abstract
Abstract A television display apparatus includes a character generator (36) for producing alphanumeric or graphic characters to be displayed along with, or in place of, the video information in a received video signal. An oscillator (18), asynchronous with a horizontal synchronizing component of the video signal (being a free-running oscillator or an oscillator locked to a multiple of the color subcarrier frequency of the video signal), supplies a clock signal to the character generator for controlling the timing of displayed character elements. A delay circuit (600), coupled in the clock signal input path to the character generator (36) or (Fig. 1) to the output of the character generator, imparts an effective delay to the character elements dependent on the time relationship between the clock signals as produced by the oscillator and the horizontal synchronizing component of the video signal. The delay compensates for temporal and spatial distortions of displayed characters which otherwise could occur.
Inventors
- 👤 Juri Tults
- 👤 Donald Henry Willis
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 21:18
CPC Classifications
G; G09; G09G; G09G5/00; G09G5/12; H; H04; H04N; H04N5/00; H04N5/44; H04N5/445; H04N5/44504
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
165 words
Television display apparatus comprising: video processing means (20) coupled to supply a video output signal to a display means (32), said video output signal having a horizontal synchronizing component; oscillator means (18;116/118) for providing a clock signal asynchronous with said horizontal synchronizing component; and character generating means (36;126) having an output coupled to said display means (32;124) for supplying a character signal thereto in raster scan form for display with said video signal in said display means, each line of said character signal comprising a plurality of character elements, said character generator means having a timing clock input coupled via a clock signal path to said oscillator means for controlling the timing of said character elements in accordance with a clock signal supplied to it through said clock signal path; characterized by synchronization means (40/22;600/22;140/150/160/122) for imparting a delay to the presentation of said character signal to said display means in response to the time relationship between said horizontal synchronization component and said clock signal.
Claim 2
Dependent Claim
165 words
Television display apparatus comprising: video processing means (20) coupled to supply a video output signal to a display means (32), said video output signal having a horizontal synchronizing component; oscillator means (18;116/118) for providing a clock signal asynchronous with said horizontal synchronizing component; and character generating means (36;126) having an output coupled to said display means (32;124) for supplying a character signal thereto in raster scan form for display with said video signal in said display means, each line of said character signal comprising a plurality of character elements, said character generator means having a timing clock input coupled via a clock signal path to said oscillator means for controlling the timing of said character elements in accordance with a clock signal supplied to it through said clock signal path; characterized by synchronization means (40/22;600/22;140/150/160/122) for imparting a delay to the presentation of said character signal to said display means in response to the time relationship between said horizontal synchronization component and said clock signal.
Claim 3
Dependent Claim
32 words
Television apparatus as recited in Claim 1, wherein said synchronization means (40/22) for imparting a delay is interposed in a path between said character generator means (36) and said display means (32).
Claim 4
Dependent Claim
69 words
Television apparatus as recited in claim 2, wherein said character generator means (36) is of a type providing R,G,B, and blanking output signals and said synchronization means (40/22) for imparting a delay comprises a respective delay means (402,404,406,408) for each of said R,G,B, and blanking output signals and circuit means (410) for applying a skew indicating signal (skew data BO-B4) to a control input each of said delay means.
Claim 5
Dependent Claim
53 words
Television apparatus as recited in claim 1, wherein said synchronization means (600/22;140/150/160/122) imparting a delay is interposed in a path between said oscillator means (18) and said character generator means (36) and produces a delayed clock signal which is applied to said character generator means for controlling the timing of said character elements.
Claim 6
Dependent Claim
42 words
Television apparatus as recited in any preceding claim, wherein said synchronization means comprises: delay means (201-208;508,510,512....N) having a plurality of taps; an output terminal; and selector means (211-238;502,506) for selectively coupling said taps to said output terminal dependent on said time relationship.
Claim 7
Dependent Claim
101 words
Television apparatus as recited in claim 1 wherein said oscillator means (116/118) comprises a free-running oscillator, and said synchronization means (130/140/150/122) is interposed in a path between said oscillator and said character generator means (126) and comprises: delay means (130:201-208) having a plurality of taps (Pl-P8); control means (140) coupled to said taps for detecting transitions of delayed clock signal phases with respect to said horizontal synchronizing component (HS) of said video output signal and providing a control signal (S8':Ql-Q8); an output terminal; and selector means (150) responsive to said control signal for selectively coupling said taps to said output terminal.
Claim 8
Dependent Claim
118 words
Television apparatus as recited in claim 6 wherein: said delay means (130:201-208) is coupled to said oscillator means (116/118) for providing a plurality of phases (P1-P8) of said clock signal (S2') at said taps: said control means (140) is coupled to said delay means (130) for providing an indicator signal (Q1-Q8) for identifying one of said phases having a specified timing relation to said horizontal synchronizing component (HS) of said video output signal; and said selector means (150:231-238) is coupled to said taps and is responsive to said indicator signal for coupling said one of said phases to said timing clock input of said character generator means (126) for reducing line-to-line variations in timing of said character elements.
References Cited (Backward Citations)
No citation records indexed.
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