Gamma Accuracy in Quantized Display Systems
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Solution Overview
Problem
Existing digital image processing systems face challenges in achieving accurate gamma correction and maintaining commercially reasonable bit depth representations, leading to issues like banding and contouring due to mismatched input and output gamma curves, especially in non-ideal display devices.
Innovation Solution
Implementing a system with matched input and output gamma curves that are exact inverses of each other, using scaled and interpolated versions of measured display gamma curves, and adjusting the starting slope of the gamma curve to ensure linearity and reduce errors, along with techniques like Catmul-Rom cubic interpolation and gamma Look Up Tables to control display output brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If matched input and output gamma curves that are exact inverses are implemented, then gamma accuracy is improved, but device complexity increases due to requiring precise curve matching and interpolation
Solution Approach 1:
The patent pre-calculates and stores gamma correction values in lookup tables before runtime processing. The system measures the actual display gamma curve in advance, then creates matched input and output gamma curves as exact inverses, storing them in LUTs for efficient retrieval during image processing, eliminating the need for complex real-time calculations
Solution Approach 2:
The patent introduces gamma lookup tables as intermediary structures that mediate between the input gamma curve and output gamma curve. These LUTs act as pre-computed translation layers that simplify the gamma correction process, allowing the system to achieve precise gamma accuracy without implementing complex real-time curve inversion algorithms
2Measurement precision
If scaled and interpolated versions of measured display gamma curves are used, then gamma accuracy is improved, but manufacturing precision requirements increase for curve measurement and interpolation
Solution Approach 1:
The system performs gamma curve measurement and interpolation in advance during system setup or calibration, storing the results in lookup tables. This preliminary action allows for careful, high-precision measurement without time constraints during actual image processing, and the interpolated values are pre-computed and stored for efficient retrieval
Solution Approach 2:
The patent creates idealized versions of the measured gamma curve through mathematical interpolation and scaling operations. Instead of relying on potentially noisy direct measurements, the system generates smooth, mathematically precise copies of the gamma curve using interpolation algorithms that eliminate measurement artifacts while preserving the essential characteristics
3Loss of information
If the starting slope of the gamma curve is adjusted to ensure linearity, then quantization error is reduced, but device complexity increases due to additional curve adjustment parameters
Solution Approach 1:
The patent modifies the gamma curve parameters, specifically adjusting the starting slope to ensure linearity in the critical low-brightness region. This parameter adjustment optimizes the distribution of quantization levels, ensuring that quantization error is minimized where the human eye is most sensitive to brightness differences, while the modified parameters are simply stored in the lookup table
Data Source
AI summary
Embodiments for providing increased gamma accuracy in quantized display systems are herein described. Both system and method embodiments are provided to enhance image quality in three primary and multiprimary display systems.