Variable Gamma Display Control for OLED Banding Reduction
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Solution Overview
Problem
Digital displays, such as OLED and LED displays, often exhibit banding due to perceivable changes in luminosity across grayscale values when calibrated to a fixed gamma value of 2.2, leading to suboptimal visual performance.
Innovation Solution
A display control system and method that calibrate the display to achieve gamma values higher than 2.2 at low grayscale values, gradually decreasing to 2.2 as grayscale values increase, using a lookup table to determine power magnitudes for each pixel, thereby minimizing perceivable luminance changes and preventing banding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the display is calibrated to a fixed gamma value of 2.2, then the display achieves standard luminance response, but banding appears due to perceivable changes in luminosity across grayscale values
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed gamma value of 2.2 to a variable gamma approach where the gamma value changes across different grayscale ranges. Specifically, the system uses gamma values greater than 2.2 (e.g., 2.5-2.8) for lower grayscale values and transitions to gamma of 2.2 for higher grayscale values, making the gamma characteristic dynamic rather than static to eliminate banding while maintaining standard response where needed
Solution Approach 2:
The patent implements parameter changes by modifying the gamma parameter across different operating conditions (grayscale ranges). The lookup table stores different gamma values corresponding to different grayscale input ranges, allowing the system to change the gamma parameter dynamically based on the input signal level, thereby resolving the banding issue while preserving standard luminance response characteristics
2Object-affected harmful factors
If gamma values greater than 2.2 are used for low grayscale values, then banding is minimized, but the display deviates from standard gamma 2.2 calibration
Solution Approach 1:
The patent applies local quality by applying different gamma values to different parts of the grayscale range. Specifically, gamma values greater than 2.2 are applied locally to the lower grayscale range (e.g., grayscale 0-63) where banding is most perceptible, while standard gamma 2.2 is maintained for the higher grayscale range, thus resolving banding locally without compromising overall standard calibration
Solution Approach 2:
The patent segments the grayscale range into multiple portions, each with its own gamma value. The lookup table divides the 256 grayscale values into segments (e.g., first portion for grayscale 0-63 with gamma > 2.2, second portion for grayscale 64-255 with gamma = 2.2), allowing different gamma characteristics to be applied to different segments to simultaneously eliminate banding and maintain standard calibration
Data Source
AI summary
A display control system includes: a display including a plurality of pixels; a lookup table including grayscale values and magnitudes of power corresponding to the grayscale values, respectively, where first ones of the grayscale values that are less than a predetermined grayscale value are calibrated based on the display achieving a gamma of greater than 2.2 and second ones of the grayscale values that are greater than the predetermined grayscale value are calibrated based on the display achieving a gamma of 2.2; a driver module configured to: based on a grayscale pixel map including a grayscale value for each pixel of the display, determine magnitudes of power to apply to pixels, respectively, using the lookup table; and apply power to the pixels of the display according to the determined magnitudes of power, respectively.