Method and apparatus for avoiding image flicker in an optical projection display
AssigneeHewlett-Packard Development Company, L.P.
InventorGregg S. Goyins
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Abstract
One embodiment of the invention is a digital filter that avoids image flicker in a projection display that has two operational modes. This digital filter avoids undesired intensity variations between successive frames by changing all the assigned pixel values by the same amount during either of the two modes. This digital filter typically only needs to correct some of the least significant bits (“LSB's”) of the pixel values during either operational mode. This is because the dynamic range of the flicker is often very limited (e.g., it is often less than 5%). In fact, some embodiments combine the flicker-filtering function with the dither-control function, if the correction of a LSB causes an over correction of the flicker problem.
Claims14
An optical projection display having a plurality of components, said components including:
- (a) a spatial light modulator,
- (b) a pixel-formatting circuit for driving the spatial light modulator in a first operational mode and a second operational mode, wherein at least one component of the projection display operates non-ideally during at least one of the modes, and
- (c) a digital filter (i) receiving assigned pixel values for driving the spatial light modulator during said operational modes, and (ii) avoiding image flicker due to the non-ideal operation of said component by changing the assigned pixels values by a uniform amount during the first operational mode and not changing the assigned pixel values during the second operational mode.
A method of avoiding flicker in images produced by an optical projection display that includes a spatial light modulator, the spatial light modulator driven in a first operational mode and a second operational mode, the method comprising:
- receiving assigned pixel values during the first and second operational modes, said pixel values for driving the spatial light modulator during the first and second operational modes, and
- changing the assigned pixels values by a uniform amount during the first operational mode and leaving unchanged the assigned pixel values during the second operational mode.
An optical projection display that has a plurality of components including a spatial light modulator, the spatial light modulator driven in an inversion mode and a non-inversion mode, wherein at least one component of the projection display operates non-ideally during at least one of the modes, a method for avoiding image flicker caused by the non-ideal operation of said component, said method comprising:
- receiving assigned pixel values during the inversion and non-inversion modes, said pixel values for generating signals to drive the spatial light modulator during the inversion and non-inversion modes, and
- changing the assigned pixels values by a uniform amount during the one of the inversion and non-inversion modes and leaving unchanged the assigned pixel values during the other one of the inversion and non-inversion modes.
An optical projection display having a plurality of components including a spatial light modulator with pixels, the projection display comprising:
- a pixel-formatting circuit operable to drive the spatial light modulator in a first operational mode and a second operational mode, wherein at least one component of said projection display operates non-ideally during at least one of said first operational mode and said second operational mode;
- and
- a digital filter (i) operable to receive assigned pixel values to drive the spatial light modulator during said first operational mode and said second operational mode, and (ii) operable to avoid image flicker due to non-ideal operation of said at least one component by modifying the assigned pixels values by a uniform amount only during said first operational mode.
Dependencies are inferred from the claim text.