Computer graphics processing and selective visual display system – Data responsive crt display control – Data responsive deflection and intensity control
Patent
1994-11-23
1997-05-06
Hjerpe, Richard
Computer graphics processing and selective visual display system
Data responsive crt display control
Data responsive deflection and intensity control
315370, G09G 104
Patent
active
056275552
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the suppression of line brightness flicker in video displays.
BACKGROUND OF THE INVENTION
In current broadcast television systems a picture or frame, is composed of two fields which are generated and transmitted sequentially in time. This method of image scanning and display is termed interlaced scanning. Interlaced scanning has various benefits, one of which is a reduction of large area image flicker which results from the presentation of each image twice per picture. However, since the two fields are off set in time, possibly by generation and certainly by transmission, artifacts are produced at vertical transitions within the displayed image. For example, an edge of a vertical transition will be portrayed by a line, or part thereof, from a single field. Thus the edge of the vertical transition is described by a signal which is present once per picture, or frame. Hence, due to the luminous decay of the display phosphor, the edge will diminish in brightness before re-illumination in the next frame. Thus, for the edge line, the interlacing process fails to raise the image display rate beyond that of human visual perception with the result that the edge defining line flickers in brightness at picture rate.
It is known that the visibility edge or line flicker may be reduced by adaptive modulation of the vertical deflection field. However, the deflection amplifier employed for such adaptive modulation requires the use two control signals. A first signal defines modulation magnitude and a second signal which controls a bridge configuration to determine deflection direction. It is desirable that an amplifier for adaptive modulation of the vertical deflection field be simplified to be responsive to a single control signal which is indicative of both magnitude and direction.
SUMMARY OF THE INVENTION
A video display comprises a CRT having a scanning electron beam describing a raster. The electron beam is deflected by a supplementary deflection means. Means coupled to a source of display video for detecting therein flicker causative signals and generating therefrom a shift signal of magnitude proportional to an amplitude of said flicker causative signals and direction signal indicative of a direction for required for flicker compensation. Means coupled to said shift signal and said direction signal for generating an analog signal. Means for coupling said analog signal to said supplementary deflection means for deflection of the electron beam by an amount related to the shift signal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of a system in accordance with an inventive arrangement.
FIG. 2 is a circuit diagram of the inventive embodiment.
FIGS. 3A and 3B illustrate constructional details of the auxiliary coil depicted in FIGS. 1 and 2, for modulation of the vertical deflection field .
DETAILED DESCRIPTION
In a video display edge or line flicker may be reduced by adaptive adjustment of the vertical deflection such that edge information is displaced on the tube face toward the object that the edge defines. In addition the adaptive adjustment or dynamic de-interlacing may be proportional to the video level or intensity of the edge, thus for a bright area the flickering edge is shifted to be adjacent to the area and effectively blend therewith. Areas with lower brightness require less edge placement shift to reduce the visibility of the flicker. The adaptive adjustment of the vertical deflection is achieved by supplementary modulation of the vertical deflection field. This supplementary modulation may be achieved by electrostatic or electromagnetic means, for example by auxiliary coils mounted on the tube neck.
FIG. 1 shows a block diagram of a line flicker reduction system in accordance with an inventive arrangement. Composite video signal V, is coupled an analog to digital converter 100. Converter 100 samples the composite video signal V, for example at 12.5 MHz. The samples are quantized into 8 bit words a+, which appear as a parallel signal at an output of con
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Line Flicker Reduction by Adaptive Adjustment of Vertical Deflection in TV Receivers, H.A. Pedersen et al. IEEE Consumer Electronics 1990, pp. 291-295.
Davenport Francis A.
Hjerpe Richard
Laks Joseph J.
Osorio Ricardo
RCA Thomson Licensing Corporation
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