LCD Gamma Correction for Brightness-Induced Transmittance Variation
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Solution Overview
Problem
Liquid crystal display (LCD) systems face variations in gamma response due to increased light intensity, leading to non-uniform and unpredictable light output, particularly in high brightness fields, as the response of liquid crystal materials is temperature-dependent and affected by localized energy increases, resulting in varying transmittance across the monitor.
Innovation Solution
A method and apparatus for compensating LCD response variations by estimating individual backlight power levels, determining combined backlight power, and correcting initial LCD code values based on changes in transmittance, using a model that describes the differential transmittance behavior of type 1 and type 2 LCD panels to achieve target transmittance levels, and an optical power measurement device coupled with a compensation module to adjust code values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high brightness backlight power levels are used to increase display brightness, then brightness is improved, but gamma response uniformity deteriorates due to temperature-dependent liquid crystal material variations
Solution Approach 1:
The system performs preliminary characterization of the LCD panel at multiple backlight power levels during manufacturing or setup. Gamma response data is collected and stored in a lookup table before actual operation, enabling real-time compensation without requiring complex calculations during display operation.
Solution Approach 2:
The system changes the operational parameters by using multiple backlight power levels (PL1, PL2, PL3) and characterizing gamma response at each level. The compensation mechanism adjusts the gamma correction based on the actual backlight power level being used, thereby maintaining uniformity across different brightness conditions.
2Power
If localized energy increases occur in high brightness fields, then brightness is improved, but transmittance uniformity deteriorates across the monitor
Solution Approach 1:
The backlight system is divided into multiple independent power levels (PL1, PL2, PL3) that can be individually characterized. The display area is segmented into regions that may have different transmittance characteristics, and compensation is applied locally based on the specific backlight power level and region.
Solution Approach 2:
The system uses measured gamma response data from the actual LCD panel to create compensation lookup tables. This feedback mechanism allows the system to adapt to the specific characteristics of each panel, compensating for manufacturing variations and maintaining uniform transmittance across different backlight power levels.
3Reliability
If gamma correction is applied to maintain response uniformity, then gamma response uniformity is improved, but device complexity increases due to multiple lookup tables and compensation algorithms
Solution Approach 1:
All complex characterization and calculation work is performed in advance during setup or manufacturing. Gamma response measurements are taken at multiple backlight power levels, and compensation lookup tables are pre-computed and stored. During normal operation, the system only needs to query these pre-computed tables, significantly reducing real-time computational complexity.
Solution Approach 2:
The system uses lookup tables with fixed-size data structures that can be easily stored in memory. Rather than implementing complex real-time calculation algorithms, the system uses pre-computed correction values that are simple to access and apply, trading off initial characterization effort for operational simplicity.
Data Source
AI summary
A method for compensation of liquid crystal display response variations in high brightness fields, comprising receiving an image signal having a set of initial liquid crystal display code values for a region, estimating individual backlight power levels for the region of the image signal, determining a combined backlight power level based on the individual backlight power levels of the region, determining at least one change in transmittance based on the combined backlight power level of the region and correcting the set of initial liquid crystal display code values based in the determined at least one change in transmittance.