Method for transforming three colors input signals to four or more output signals for a color display

Abstract

A method for transforming three color input signals (R, G, B) corresponding to three gamut defining color primaries to four color output signals (R′, G′, B′, W) corresponding to the gamut defining color primaries and one additional color primary W for driving a display having emitters that emit light corresponding to the to the four color output signals including calculating a common signal value S as a function F1 of the three color input signals (R,G,B) for a current and neighboring pixels; determining a final common signal value S′ based upon the common signals for the current and neighboring pixels; calculating the three color signals (R′,G′,B′) by calculating a value of a function F2 of the final common signal value S′ and adding it to each of the three color input signals (R,G,B); and calculating the output signal W as a function F3 of the final common signal value S′.

Description

FIELD OF THE INVENTION [0001] The present invention relates to color processing three color image signals for display on a color OLED display having four or more color primaries. BACKGROUND OF THE INVENTION [0002] Additive color digital image display devices are well known and are based upon a variety of technologies such as cathode ray tubes, liquid crystal modulators, and solid-state light emitters such as Organic Light Emitting Diodes (OLEDs). In a common OLED color display device a pixel includes red, green, and blue colored OLEDs. These light emitting color primaries define a color gamut, and by additively combining the illumination from each of these three OLEDs, i.e. with the integrative capabilities of the human visual system, a wide variety of colors can be achieved. OLEDs may be used to generate color directly using organic materials that are doped to emit energy in desired portions of the electromagnetic spectrum, or alternatively, broadband emitting (apparently white) OL...

AI Technical Summary

Benefits of technology

[0012] The present invention has the advantage of providing an efficient method for transforming a three color input image signal that may have been sampled for display on a display with three spatially non-overlapping light emitting elements to a four or more color image signal in a way that preserves edge information in the OLED display system.

Problems solved by technology

These methods are complicated by image structure limitations because they typically involve non-continuous tone systems, but because the white of a subtractive CMYK image is determined by the substrate on which it is printed, these methods remain relatively simple with respect to color processing.

Attempting to apply analogous algorithms in continuous tone additive color systems would cause color errors if the additional primary is different in color from the display system white point.

The scaling is ostensibly to try to correct the color errors resulting from the brightness addition provided by the white, but simple correction by scaling will never restore, for all colors, all of the color saturation lost in the addition of white.

The lack of a subtraction step in this method ensures color errors in at least some colors.

Additionally, Morgan's disclosure describes a problem that arises if the white primary is different in color from the desired white point of a display device without adequately solving it.

The method simply accepts an average effective white point, which effectively limits the choice of white primary color to a narrow range around the white point of the device.

Because of its similarity to the CMYK algorithm, it suffers from the same problem cited above, namely that a white pixel having a color different from that of the display white point will cause color errors.

While this patent does mention providing sampling of the data for a display device having four different color light emitting elements, it does not provide a method for converting from a traditional three color image signal to an image signal that is appropriate for display on a display device having four different color light emitting elements.

While it is possible to resample data from one intended spatial arrangement to a logical display with spatially overlapping light emitting elements; performing a conversion from the image three color image signal to a four color OLED display, and then resampling the data to the spatial arrangement of the OLED display; is computationally intensive.

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