Image Processing Tone Conversion for HDR Signal Stability
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Solution Overview
Problem
HDR camera systems face image quality degradation due to amplitude level differences between luminance and color components during tone conversion, particularly when converting signals for HDR displays, leading to pseudo signals and impaired image quality.
Innovation Solution
An image processing apparatus that performs optimized tone conversion processing for both luminance and color systems, using separate conversion units to generate and combine color component data, and a correction unit to ensure non-negative values, thereby suppressing signal levels near 0 and preventing image quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optimized tone conversion processing is performed for luminance and color systems separately, then image quality can be improved, but signal level differences between luminance and color components are amplified
Solution Approach 1:
The patent divides the tone conversion process into separate luminance system processing and color system processing paths. The luminance component is processed through one conversion path while the color difference component is processed through another path, allowing independent optimization of each system's tone conversion characteristics.
Solution Approach 2:
The patent applies different tone conversion characteristics (parameters) to the luminance and color difference components. By changing the conversion parameters separately for each component type, the system optimizes image quality while the correction unit ensures signal level stability by adjusting for amplitude differences.
2Adaptability or versatility
If HDR tone conversion is applied, then color gamut and display luminance are improved, but pseudo signals are generated due to amplitude level differences
Solution Approach 1:
The patent separates luminance and color difference processing to apply appropriate HDR tone conversion characteristics to each component independently, enabling wider color gamut representation while preventing pseudo signal generation through proper component handling.
Solution Approach 2:
The correction unit acts as an intermediary that processes the tone-converted signals and corrects amplitude level differences between luminance and color components, preventing pseudo signal generation while maintaining HDR benefits.
3Illumination intensity
If gamma conversion with sharp rising edge is applied for HDR, then dark portion contrast is improved, but amplitude level differences between luminance and color components are enhanced
Solution Approach 1:
The patent applies the sharp rising edge gamma conversion characteristic specifically to the luminance component to improve dark portion contrast, while processing the color difference component separately to maintain amplitude level consistency between components.
Solution Approach 2:
The patent applies different tone conversion characteristics to different components: the luminance component receives the HDR-optimized sharp rising edge conversion for improved dark contrast, while the color difference component receives conversion that maintains amplitude consistency with luminance.
Data Source
AI summary
An apparatus has first and second generation units which generate, from input image data, color component data for luminance output and color component for color difference output, first and second convertors which converts tones of each piece of the color component data for luminance output and for color difference output, a combining unit combining each piece of the color component data obtained by the first and second convertors to generate respective pieces of combined color component data; a separation unit respectively separating luminance data and color difference data from the combined color component data; and a correction unit correcting a tone of each of the luminance data and color difference data. The second convertor has a characteristic for outputting a non-negative value in a range, of negative infinity to a positive threshold set in advance.