Adaptive Gamma Control for Variable Refresh Rate Flicker
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Displays using variable refresh rates often experience luminance changes, leading to flicker effects that detract from the user experience due to the longer vertical blanking periods in LCDs and other display types.
Innovation Solution
The system employs plural gamma lookup tables stored in a display scalar, allowing for real-time gamma adjustment based on the selected refresh rate to maintain uniform luminance by switching between different gamma lookup tables during vertical blanking periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If variable refresh rate is used to synchronize display with rendering frame rate, then image tearing and stuttering are prevented, but luminance changes occur causing flicker effects
Solution Approach 1:
The patent applies parameter changes by adjusting the gamma value based on the refresh rate. Multiple gamma values are stored in a lookup table, and the appropriate gamma value is selected according to the current refresh rate. This compensates for the luminance changes caused by variable refresh rate, maintaining consistent perceived brightness while allowing refresh rate to vary for tear-free rendering.
Solution Approach 2:
The patent introduces gamma correction as an intermediary mechanism between the variable refresh rate control and the display output. The gamma lookup table acts as a mediator that translates refresh rate changes into corresponding gamma adjustments, thereby indirectly compensating for luminance variations without directly controlling the refresh rate itself.
2Stability of the object's composition
If longer vertical blanking period is used to hold charges at LCD pixels, then image hold is improved, but luminance change vulnerability increases causing flicker
Solution Approach 1:
The patent changes the gamma parameter in response to variations in vertical blanking period duration. When the vertical blanking period is longer, a different gamma value is selected to compensate for the increased vulnerability to luminance change, thereby maintaining stable perceived luminance despite the longer hold period.
3Illumination intensity
If gamma lookup table is changed in real-time during vertical blanking, then luminance uniformity is maintained, but additional processing complexity is introduced
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing multiple gamma values in a lookup table during manufacturing or initialization. These gamma values are predetermined for different refresh rates, eliminating the need for complex real-time calculations. The system only needs to lookup and apply the appropriate pre-computed gamma value based on the current refresh rate.
Solution Approach 2:
The patent replaces complex real-time gamma calculation mechanics with a simpler lookup table mechanism. Instead of performing computationally intensive gamma calculations during vertical blanking, the system substitutes this with a simple memory lookup and value assignment operation, significantly reducing processing complexity while maintaining luminance uniformity.
Data Source
AI summary
An information handling system presents visual images at a display through a scalar that adjusts the visual images with a gamma lookup table selected from plural gamma lookup tables based upon a refresh rate of the display. As a graphics processor commands variable refresh rates, a blanking period is used to adjust the refresh rates and a gamma lookup table selection is applied during the blanking period to encourage uniform luminance. Each gamma lookup table is stored in a separate SRAM and input to a multiplexor that uses the refresh rate to select which gamma adjusted visual image is presented at the display.