RGBW Display Filter Processing for Moire Suppression
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Solution Overview
Problem
In display devices using four colors of sub-pixels, existing technologies face challenges in maintaining image quality due to band limitations that result in information loss and moire and false color issues.
Innovation Solution
An image processing device with specific filter processing sections that limit frequency bands based on the arrangement of sub-pixels, including a first filter processing section for white sub-pixels and separate sections for red, green, and blue sub-pixels, allowing phase inversion in certain bands to suppress moire and false colors, while enhancing resolution based on sub-pixel characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the band of the image signal is limited for each of the colors independently, then the moire caused by alias is suppressed, but the information lost from the original image increases
Solution Approach 1:
The patent applies different filter characteristics to different color channels based on their specific requirements. The green channel uses a filter with wider passband and higher cutoff frequency to preserve spatial frequency information, while red and blue channels use filters with narrower passbands. This local differentiation of filter quality allows each color channel to be optimized independently, suppressing moire where needed while preserving information where the human eye is less sensitive.
Solution Approach 2:
The patent changes the filter parameters (cutoff frequency, passband width) differently for each color channel. Specifically, the green channel filter has a cutoff frequency of 0.5 or higher in the vertical direction and 0.4 or higher in the horizontal direction, while red and blue channel filters have lower cutoff frequencies. This parameter differentiation allows the system to maintain higher resolution for green channels while still suppressing moire effects across all channels.
2Object-affected harmful factors
If the frequency band is limited to a half in both vertical and lateral directions for R and B image signals, then the moire caused by high-frequency component is prevented, but the resolution of the displayed image decreases
Solution Approach 1:
The patent segments the filter processing into separate channels (red, green, blue) with different filter characteristics. Instead of applying a uniform half-frequency limitation to all channels, the system segments the frequency limitation strategy: green channel maintains higher frequency content while red and blue channels receive more aggressive filtering. This segmentation allows the system to optimize for both moire prevention and resolution preservation.
Solution Approach 2:
The patent implements different frequency limit parameters for different color channels. The green channel filter allows frequencies up to 0.5 or higher in the vertical direction and 0.4 or higher in the horizontal direction, while red and blue channel filters limit frequencies more aggressively. This parameter change strategy enables the system to maintain resolution where the human eye is less sensitive to aliasing artifacts.
3Illumination intensity
If four colors of sub-pixels are used for color display, then the color reproducibility and brightness are improved, but the complexity of the image processing system increases
Solution Approach 1:
The patent applies different filter processing to different color channels based on their specific characteristics and the human eye's sensitivity. The green channel receives different filtering treatment compared to red and blue channels, allowing each channel to be optimized for its specific role in the RGBW display system. This local quality approach manages the complexity by treating each channel according to its unique requirements rather than applying a uniform processing strategy.
Data Source
AI summary
An image processing device supplies an image signal to a display device having pixels being composed mainly of four sub-pixels arranged two by two in a first direction and a second direction. The image processing device includes a first filter processing section adapted to perform a filter process of limiting frequency bands in the first direction and the second direction of the image signal adapted to display a first sub-pixel corresponding to white in a manner corresponding to an arrangement of both of the first sub-pixel and a second sub-pixel located in a diagonal direction with respect to the first sub-pixel, and a second filter processing section adapted to perform a filter process of limiting frequency bands in the first direction and the second direction of the image signal adapted to display the second sub-pixel in a manner corresponding to an arrangement of the first sub-pixel and the second sub-pixel.