Digital display unit of a computer system having an improved method and apparatus for sampling analog display signals

DETAILED DESCRIPTION The present invention is directed to a method and apparatus for generating a sampling clock signal for sampling an analog display signal received by a digital display unit.
The sampling clock is generated such that display artifacts caused by high frequency noise signals may be substantially reduced (or eliminated) in the display of successive image frames encoded in a wide bandwidth analog display signal.
In accordance with the present invention, a clock generator in a display unit first generates an intermediate clock signal synchronized with the synchronization signals in a received analog display signal.
Due to the synchronization, the analog display signal may be generally sampled in the samples duration if the intermediate clock signal were to be used as a sampling clock.
However, the sampling clock used for sampling the analog display signal is generated in accordance with the present invention by modulating the intermediate clock by different phase delay amounts for successive image frames (or horizontal lines).
Due to the different phase delays, samples are taken at different sampling points for successive image frames for the same pixel position.
The amount of phase delay is maintained to be small enough such that the samples are again taken in the samples duration.
The effect of displaying the sampled values on many digital display units (e.
g.
, flat panel monitors) is that the image for the pixel position is perceived as if the sampled values are passed through a low-pass filter.
This is because of at least one of two reasons--(1) the display units generally respond slowly to changes in image intensity, and (2) the human eye generally perceives an average intensity when a display is varied in quick succession.
It may be noted that the filtering action is temporal in nature, that is, the average of intensities across a few successive frames is perceived for each pixel position (point) on a digital display screen.
As a result of the low-pass filter action, each pixel position on a display screen is perceived to have been displayed with an average of the sampled data values for the pixel position