Liquid Crystal Display Gamma Curve Adjustment for External Light
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Solution Overview
Problem
Liquid crystal displays experience image quality distortion due to external light variations, as they maintain a fixed gamma curve regardless of environmental changes, leading to inconsistent relative brightness and linearity across gray levels.
Innovation Solution
A liquid crystal display system incorporating an external light sensing unit and a gamma curve adjusting circuit that modulates digital video data based on illuminance, adjusting gamma curves to maintain relative brightness at an original level and ensure linearity across all gray levels, using techniques such as data bit expansion and variable resistor adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed gamma curve is used for displaying images, then the display system maintains simplicity and consistent performance under standard conditions, but the image quality becomes distorted when external light conditions change
Solution Approach 1:
The patent implements dynamic gamma curve adjustment by sensing external light illuminance and automatically selecting appropriate gamma curves from multiple pre-stored options. The system transitions from a static fixed gamma curve to a dynamic adaptive gamma curve that changes based on environmental light conditions, resolving the contradiction between reliability and adaptability
Solution Approach 2:
The patent employs a feedback mechanism where an external light sensor continuously monitors the illuminance level and provides this information to the gamma curve selection circuit. This closed-loop feedback system enables automatic adaptation to changing light conditions, maintaining image quality consistency across different environments
2Reliability
If the gamma curve is adjusted to compensate for external light changes, then the relative brightness and linearity of gray levels are maintained, but the system complexity increases due to additional sensing and control circuits
Solution Approach 1:
The patent applies preliminary action by pre-storing multiple gamma curves corresponding to different illuminance levels in the gamma curve selection circuit. When external light conditions change, the system simply selects from these pre-prepared curves rather than calculating new curves in real-time, thereby maintaining image quality while minimizing the complexity of the adjustment circuit
Solution Approach 2:
The patent changes the parameter of gamma curve selection based on illuminance level rather than attempting to dynamically generate entirely new curves. This approach maintains brightness linearity across gray levels by selecting from a finite set of optimized curves, reducing the computational and circuit complexity compared to continuous gamma adjustment
Data Source
AI summary
A liquid crystal display and a method of driving the same are disclosed. The liquid crystal display includes a liquid crystal display panel for displaying an image, an external light sensing unit for sensing an illuminance of external light around the liquid crystal display panel, a backlight unit whose an output luminance is controlled by an adjustment dimming signal, and a gamma curve adjusting circuit for modulating digital video data or varying resistances of variable resistors constituting a gamma resistor string based on the illuminance of external light or according to a relative maximum white luminance based on the adjustment dimming signal, so as to uniformly keep a relative brightness of the input image a user perceives irrespective of changes in the illuminance of external light.