Multi-primary Conversion Luminance Matching for Display Readability
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Solution Overview
Problem
Existing sub-pixel rendering algorithms for multi-primary displays, such as RGBW, struggle to maintain readability of text and representation of fine details and graphic images due to limitations in reproducing luminance gradients.
Innovation Solution
A conversion method that constrains multi-primary conversion to match local display luminances with corresponding input luminances, using filtering operations with proportional filter coefficients to optimize the distribution of drive signals across sub-pixels, ensuring accurate reproduction of luminance gradients and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If existing sub-pixel rendering algorithms are used for multi-primary displays, then the display can show full color reproduction with increased brightness, but the readability of text and representation of fine details deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different regions in the display. Luminance points are classified into text regions and non-text regions, with different rendering strategies applied to each. Text regions use a rendering approach that prioritizes readability and edge sharpness, while non-text regions can utilize the full multi-primary capabilities for color reproduction and brightness enhancement.
Solution Approach 2:
The patent segments the display content into different types (text vs. non-text) and applies different sub-pixel rendering algorithms to each segment. This segmentation allows the system to optimize for readability in text areas while maintaining color accuracy and brightness in graphical areas, thereby resolving the contradiction between brightness and text readability.
2Device complexity
If multi-primary conversion is performed without luminance gradient constraint, then the conversion complexity is reduced, but the reproduction of luminance gradients and image quality deteriorates
Solution Approach 1:
The patent implements feedback by computing luminance gradients from the input image and using this information to constrain the multi-primary conversion process. The luminance gradient values are fed back into the conversion algorithm to guide the distribution of drive signals to sub-pixels, ensuring that the output luminance gradients match the input gradients. This feedback mechanism maintains image quality without requiring overly complex conversion processes.
Solution Approach 2:
The patent changes parameters by introducing luminance gradient values as additional constraints in the multi-primary conversion process. Instead of performing a simple color space transformation, the system adjusts the conversion parameters to account for luminance gradients, thereby improving luminance gradient reproduction accuracy while keeping the overall conversion framework manageable.
3Device complexity
If pixel resolution is reduced using multi-primary display, then the number of drivers can be reduced, but the resolution and detail representation deteriorates
Solution Approach 1:
The patent exploits another dimension by utilizing the temporal dimension through frame buffering and the spatial dimension through sub-pixel rendering. By distributing luminance information across multiple sub-pixels within the same pixel location and across neighboring pixels, the system achieves higher effective resolution without increasing the physical pixel count or driver complexity. The multi-primary sub-pixels (R, G, B, W) provide additional degrees of freedom for rendering high-resolution images with fewer drivers.
Data Source
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AI summary
A method converts an input image signal (IS) into a drive signal (DS) for driving sub-pixels (SP) of a display device (DD) comprising display pixels (DPI) having at least two sub-pixel groups (SGl, SG2) being able to contribute to luminance information displayed. The conversion comprises a multi-primary conversion (MPC) which receives the input image signal (IS) and which is performed under a constraint (CO). The constraint (CO) is determined (CD) by substantially matching local display luminances (DLl, DL2; DLD) associated with the at least two sub-pixel groups (SGl, SG2) with corresponding local input luminances (Ll, L2; LD) of input pixels (IP) of the input image signal (IS), thereby obtaining a display luminance pattern defined by the display pixels (DPI) corresponding to an input luminance pattern defined by the input pixels (IP) associated with the display pixels (DPI).