LCD Color Gamut Mapping for High Luminance Output

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Solution Overview

Problem

Liquid crystal display (LCD) apparatuses have limited luminance values for colors, resulting in displayed colors having lower luminance than the maximum luminance of full white due to their triangular color gamut in a two-dimensional color coordinate system, which restricts the production of high luminance colors.

Innovation Solution

A method and apparatus for processing image signals that involve converting source image signals into a color space for gamut mapping, reducing the color gamut, and mapping colors within the reduced gamut to match the display color gamut, using techniques like clipping algorithms and extending the color gamut of YCbCr signals to xvYCC color space, while adjusting white levels and applying gamma curves to achieve high luminance colors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the LCD apparatus uses three primary color coordinates (red, green, blue) to display colors, then the color gamut coverage is improved, but the luminance values of displayed colors are lower than the maximum luminance of full white

Engineering Contradiction:

Improvecolor gamut coverageVSAvoidluminance value

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The patent transforms the color signal from a nonlinear color space to a linear color space, and then applies gamma correction with a gamma value greater than 1 to the linear color signal. This parameter transformation allows the displayed color to have higher luminance while maintaining color accuracy, resolving the contradiction between color gamut coverage and luminance value.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs color space conversion to a linear color space before gamma correction, and pre-calculates the gamma correction values based on the desired luminance enhancement. This preliminary processing ensures that the luminance enhancement is applied correctly to achieve high luminance colors without compromising color gamut coverage.

Inventive Principle:

Principle #10Preliminary action

2Illumination intensity

If the color gamut is reduced to produce high luminance colors, then the luminance value is improved, but the color range may be limited

Engineering Contradiction:

Improveluminance valueVSAvoidcolor range

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent uses parameter transformation between linear and nonlinear color spaces with gamma correction to achieve luminance enhancement without permanently reducing the color gamut. The color range is preserved in the linear color space while luminance is enhanced through gamma correction application.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent dynamically adjusts the gamma correction parameter to balance between luminance enhancement and color range preservation. By making the gamma value adjustable, the system can optimize the trade-off between achieving high luminance colors and maintaining adequate color gamut coverage based on display requirements.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8928685B2Method of displaying image and display apparatus for performing the same

Publication Date: 2015.01.06 SAMSUNG DISPLAY CO LTD

AI summary

A method of processing an image signal includes: converting a source image signal into an image signal corresponding to a color space for a color gamut mapping; reducing a color gamut of the image signal; and mapping the image signal corresponding to colors within the reduced color gamut into an image signal corresponding to colors within a display color gamut, wherein the colors of the display color gamut are displayed by a display panel.