Computer graphics processing and selective visual display system – Plural display systems – Diverse systems
Patent
1996-04-10
1998-08-04
Hjerpe, Richard A.
Computer graphics processing and selective visual display system
Plural display systems
Diverse systems
345 58, 345 93, G09G 500
Patent
active
057900833
ABSTRACT:
A graphics controller drives a flat-panel display and simultaneously drives an external cathode-ray-tube (CRT) display. Horizontal clock pulses continue to be applied to the flat panel during the CRT's vertical blanking or re-trace period so that the flat panel is not left in a constant state during the entire re-trace period. Leaving the flat panel in a constant state for a long period of time can cause flicker or delayed response immediately after the re-trace period ends. Running the horizontal clocks during the re-trace period can lead to D.C. buildup or rolling flicker, believed to be caused by a polarity-inversion counter in the panel assembly which is not designed to receive additional horizontal clocks beyond the number of lines on the flat panel. D.C. buildup in the flat panel is reduced by adding a high-frequency burst of horizontal clock pulses to the flat panel during the CRT's vertical re-trace period. The burst of clock pulses adjusts the count in the polarity-inversion counter. The number of pulses in the burst is programmable so that the optimum number of pulses in the burst can be determined empirically and adjusted for different panel manufacturers.
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Auvinen Stuart T.
Hjerpe Richard A.
NeoMagic Corp.
Nguyen Francis N.
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