Reducing sparkle artifacts with low brightness processing
AssigneeThomson Licensing
InventorsDonald Henry Willis, John Alan Hague
Life of this patent
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Abstract
A method for reducing sparkle artifacts in a liquid crystal imager, comprises the steps of: low pass filtering only a first lower brightness level signal component of a video signal; and, slew rate limiting only a second lower brightness level signal component of the video signal having the low pass filtered signal component, the video signal having the low pass filtered and the slew rate limited signal components being less likely to result in sparkle artifacts in the imager. Brightness thresholds for defining the lower brightness level signal components and slew rate limits can be selected in accordance with transitions between lower and higher level gain portions of a gamma table associated with the imager, for example an LCOS imager.
Claims24
A method for reducing sparkle artifacts due to non linearity in a transfer function of a liquid crystal imager comprising the steps of:
- decomposing an input video signal according to a first threshold to provide a first low brightness signal;
- low pass filtering said first low brightness signal to provide a low pass filtered low brightness signal;
- slew rate limiting said low pass filtered low brightness signal;
- and
- said providing an output video signal including said low pass filtered slew rate limited signal, said output video signal being less likely to result in sparkle artifacts in said imager.
An apparatus for reducing sparkle artifacts due to non linearity in a transfer function of a liquid crystal imager comprising:
- means for decomposing an input video signal according to a first threshold to provide a first low brightness signal;
- means for low pass filtering said first low brightness signal to provide a low pass filtered low brightness signal;
- means for slew rate limiting said low pass filtered low brightness signal;
- and
- means for providing an output video signal including said low pass filtered slew rate limited signal to said imager.
An apparatus for reducing sparkle artifacts due to non linearity in a transfer function of a liquid crystal imager comprising:
- a decomposer for providing a first low brightness signal in accordance with a first threshold;
- a low pass filter for filtering said first low brightness signal to provide a filtered low brightness signal;
- and,
- a slew rate limiter for processing said filtered low brightness signal to provide an output video signal less likely to result in sparkle artifacts in said imager.
Dependencies are inferred from the claim text.