RGBW Display Signal Processing for Luminance Efficiency
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Solution Overview
Problem
Conventional RGBW liquid crystal display devices face limitations in improving light use efficiency, especially when dealing with high saturation and varying gradation values, which restricts their ability to reduce backlight luminance and power consumption, particularly in transmissive panels.
Innovation Solution
A display device with a signal processing unit that performs color conversion on input video signals to increase luminance within allowable ranges of hue and saturation, generating additional color information that can be expressed by a fourth sub-pixel, thereby enhancing light use efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional RGBW display devices perform image extension by replacing common image data with white pixel data, then light use efficiency increases, but the ability to improve efficiency is limited when input RGB data has high saturation and/or brightness or significant gradation value differences
Solution Approach 1:
The patent converts input RGB data to an alternative color space (such as YCbCr or LMS) where luminance and chrominance are separated. By operating on luminance values independently and applying selective gamma correction or tone mapping, the system can enhance light use efficiency for luminance components while preserving chrominance information, thereby maintaining adaptability to high saturation and brightness data that limits conventional RGBW image extension methods
2Use of energy by stationary object
If conventional RGBW display devices replace common image data with white pixel data to increase transmitted light, then backlight luminance can be reduced, but power consumption reduction is limited in transmissive liquid crystal panels when there is less room for image extension
Solution Approach 1:
The patent applies different gamma correction parameters or tone mapping functions to luminance and chrominance components separately. By optimizing the luminance transfer function to maximize light transmission efficiency while maintaining perceptual quality, the system can achieve greater power consumption reduction in transmissive panels even when conventional image extension has limited room, as the parameter optimization works across all pixel types including high saturation regions
3Loss of energy
If conventional RGBW display devices use image extension to increase light transmitted through each pixel, then light use efficiency improves, but the method fails to provide sufficient efficiency improvement when gradation values of respective colors significantly differ
Solution Approach 1:
The patent separates luminance and chrominance processing by converting to an alternative color space. Luminance values undergo gamma correction or tone mapping optimized for light transmission efficiency, while chrominance values are processed separately to preserve color accuracy. This independent parameter optimization allows the system to achieve both improved light use efficiency and maintained color accuracy even when gradation values of respective colors significantly differ, overcoming the limitation of conventional RGBW image extension
Data Source
AI summary
According to an aspect, a display device includes: an image display unit in which pixels each including a plurality of sub-pixels are arranged in a matrix, the sub-pixels displaying a plurality of color components; and a signal processing unit that performs color conversion on an input video signal and outputs the resultant signal to a drive circuit that controls drive of the image display unit. The signal processing unit performs color conversion on first color information so as to increase luminance within an allowance range of a change in at least one of a hue and saturation, to generate second color information, the first color information being composed of three primary colors of red, green, and blue and derived based on the input video signal.