Adaptive Gamma Encoding for HDR Display Luminance Mapping
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Solution Overview
Problem
Conventional gamma-encoding curves become unsuitable for high brightness and high dynamic range (HDR) displays as they deviate from human visual system perception, especially at higher luminance levels, leading to inadequate luminance mapping and display response.
Innovation Solution
Implementing an alternate encoding curve derived from perceptual curves like the Digital Imaging and Communications in Medicine (DICOM) Grayscale Standard Display Curve, which maps just-noticeable difference values to output luminance values, and adjusting it based on display-specific calibration data to accommodate varying peak brightness across dual modulation displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gamma-encoding curves are used for HDR displays, then the encoding process remains simple and compatible with standard displays, but the luminance mapping becomes inaccurate and deviates from human visual perception at high brightness levels
Solution Approach 1:
The patent changes the encoding curve parameters from conventional gamma (γ=2.2) to perceptual curves (e.g., DICOM with γ≈1.8) that accurately represent human visual perception across the full luminance range. This parameter change enables accurate luminance mapping for HDR displays while maintaining the mathematical simplicity of power-law encoding functions.
2Reliability
If a fixed encoding curve is used for all luminance ranges, then the encoding process is computationally efficient, but the visual representation becomes inconsistent across different brightness levels on HDR displays
Solution Approach 1:
The patent implements adaptive gamma encoding where the encoding curve is dynamically selected or adjusted based on the peak luminance capability of the display device. The system determines the display's maximum luminance and selects an appropriate perceptual curve from a set of pre-defined curves, enabling consistent visual representation across varying brightness levels while maintaining computational efficiency through curve selection rather than continuous calculation.
3Adaptability or versatility
If gamma-encoding with γ=2.2 is applied to HDR displays with peak luminance up to 4000 cd/m², then compatibility with conventional displays is maintained, but the encoding becomes unsuitable for high brightness ranges and produces inadequate luminance mapping
Solution Approach 1:
The patent changes the encoding curve parameters from conventional gamma (γ=2.2) to perceptual curves (e.g., DICOM with γ≈1.8) that accurately represent human visual perception across the full luminance range. This parameter change enables accurate luminance mapping for HDR displays while maintaining the mathematical simplicity of power-law encoding functions.
Solution Approach 2:
The patent implements adaptive gamma encoding where the encoding curve is dynamically selected or adjusted based on the peak luminance capability of the display device. The system determines the display's maximum luminance and selects an appropriate perceptual curve from a set of pre-defined curves, enabling consistent visual representation across varying brightness levels while maintaining computational efficiency through curve selection rather than continuous calculation.
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3
AI summary
Systems and methods of image processing are provided for a display having a light source modulation layer and a display modulation layer. A section of a perceptual curve, such as a DICOM curve, is extracted for each frame of image data, based on a profile of expected luminance on the display modulation layer from light emitted by the light source modulation layer. The section of the perceptual curve may be used to determine a desired-total response curve which maps display modulation layer input control values to corresponding output luminance values. The desired-total response curve and a display modulator-specific response curve may be applied to image data to generate control values for driving the display modulation layer.