Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Patent
1995-07-07
1997-07-01
Issing, Gregory C.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
31536811, 31536817, 315370, G09G 128, H01J 2951
Patent
active
056441967
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a correction arrangement for correcting a beam landing location error in a cathode ray tube (CRT).
In some prior art projection television receivers, a correction signal such as a horizontal rate parabola signal is generated. The parabola is amplitude-modulated at a vertical rate sawtooth manner to produce a so-called bow-tie signal. The bow-tie signal is coupled via an amplifier to an auxiliary coil such as a vertical convergence auxiliary coil of a beam landing location error correction arrangement for correcting, for example, a vertical convergence error.
In the vicinity of the end of horizontal retrace, the slope of the current in the auxiliary coil changes its polarity. During a beginning portion of a horizontal trace, the rate of change or slope of the current in the auxiliary coil is, typically, at a maximum magnitude. During the immediately preceding retrace, inadequate or limited response time with respect to the horizontal rate parabola signal in the amplifier that drives the auxiliary coil may produce "bending" of horizontal scan lines that also produces a misconvergence error in the vertical direction at the extreme left side of the displayed image. The extent of "bending" increases close to the top and bottom ends of the displayed image.
In U.S. Pat. No. 5,218,275 in the name of Truskalo, entitled, Beam Landing Location Error Correction Arrangement, a horizontal rate parabolic voltage generator is responsive to a reset pulse at the horizontal rate for generating a horizontal rate parabolic voltage that includes a pulse portion in the vicinity of horizontal retrace. The parabolic voltage is coupled to an auxiliary coil mounted on a cathode ray tube to produce a vertical convergence error correction current. The pulse portion compensates for a slow response time in an amplifier that drives the auxiliary coil.
The pulse portion controls the response of the amplifier during a beginning portion of a trace interval of the deflection current. The pulse portion compensates for inadequate response time of the amplifier to provide a sufficiently large slope of the current in the auxiliary coil.
In the Truskalo arrangement, the pulse portion is produced by detecting zero crossing in a horizontal deflection current that occurs at the center of trace. The signal that is produced by the zero crossing detection is applied via a pair of one-shot multivibrators to produce the aforementioned pulse portion. Thus, the pulse portion is referenced to the detected trace, zero crossing portion.
It may be desirable to apply a retrace pulse for producing the aforementioned pulse portion, such that the need for detecting zero crossing in the trace portion is eliminated; thereby, the circuitry is advantageously simplified.
A video display deflection apparatus, embodying an aspect of the invention, includes a cathode ray tube including an evacuated glass envelope. A display screen is disposed at one end of the envelope and an electron gun assembly is disposed at a second end of the envelope. The electron gun assembly produces an electron beam that forms a raster at electron beam landing locations on the screen. A main horizontal deflection winding and a main vertical deflection winding are disposed on a neck of the cathode ray tube for producing a main deflection field in a beam path of the electron beam. The deflection field varies in a manner to vary the electron beam landing location. A horizontal deflection current is generated in the horizontal deflection winding and a first retrace pulse signal is generated during horizontal retrace. A correction signal is generated. The correction signal generating arrangement is responsive to the first retrace pulse signal for introducing a pulse portion in the correction signal. The first retrace pulse signal is utilized for controlling the pulse portion during an interval that is determined by the first retrace pulse signal. An amplifier is responsive to the correction signal for generating a current in an auxiliary deflection coil disposed on the neck t
REFERENCES:
patent: 3953760 (1976-04-01), Matsuura et al.
patent: 4318032 (1982-03-01), Kureha
patent: 4395662 (1983-07-01), Sexton, Jr.
patent: 4500816 (1985-02-01), Murphy
patent: 4560910 (1985-12-01), Midland
patent: 4675580 (1987-06-01), Dietz
patent: 4814671 (1989-03-01), Oguino
patent: 5034664 (1991-07-01), Fernsler et al.
patent: 5138238 (1992-08-01), Truskalo
patent: 5218275 (1993-06-01), Truskalo
Henig Sammy S.
Issing Gregory C.
Laks Joseph J.
Thomson Consumer Electronics Inc.
Tripoli Joseph S.
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