Display Device Degradation Compensation Using Pixel Variation Coefficients
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Solution Overview
Problem
In organic EL display devices, compensation processes that reference the average degree of degradation of all pixels can lead to accelerated degradation of significantly degraded pixels, resulting in a short compensable period and non-uniform luminance across the screen.
Innovation Solution
A display device and method that include a degree-of-degradation obtaining circuit, an index value calculating circuit, and a reference luminance or current setting circuit to determine and adjust the reference luminance or current based on the variation in degradation levels across pixels, thereby compensating for degradation and extending the compensable period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If compensation is performed by referencing the average degree of degradation of all pixels, then the compensable period is extended, but significantly degraded pixels experience accelerated degradation leading to non-uniform luminance
Solution Approach 1:
The patent segments the pixel population into multiple groups based on their degradation characteristics. Instead of applying uniform compensation to all pixels, the system divides pixels into groups (e.g., first group with lower degradation, second group with higher degradation) and applies different compensation strategies to each group. This segmentation allows the system to extend the compensable period for less degraded pixels while preventing accelerated degradation in significantly degraded pixels, thereby maintaining luminance uniformity across the display.
2Use of energy by stationary object
If constant current is supplied to the organic EL element, then power consumption is reduced, but luminance gradually decreases over time due to degradation
Solution Approach 1:
The patent implements dynamic compensation by continuously monitoring the degradation state of pixels and adjusting the drive current accordingly. The system periodically measures the luminance output of pixels under constant current conditions, calculates degradation factors, and updates compensation values. This dynamic adjustment allows the display to maintain constant luminance over time while managing power consumption, as the current is only increased when degradation is detected rather than being continuously elevated.
3Ease of manufacture
If threshold voltage of drive transistors varies due to degradation, then manufacturing simplicity is maintained, but display quality degrades due to luminance variations
Solution Approach 1:
The patent implements a feedback-based compensation system that periodically measures the actual luminance output of pixels and uses this information to adjust drive currents. The system includes monitoring circuits that measure pixel characteristics, calculate degradation factors, and generate corrected drive signals. This feedback mechanism compensates for threshold voltage variations in drive transistors without requiring higher manufacturing precision, thereby maintaining manufacturing simplicity while improving display quality and reducing luminance variations.
Data Source
AI summary
The display device is provided with a degree-of-degradation calculating circuit that determines a degree of degradation representing a level of degradation of a compensation-target circuit element included in each of K pixel circuits which are some or all of a plurality of pixel circuits; a variation coefficient calculating circuit that calculates, as a variation coefficient, a value depending on a deviation determined based on degrees of degradation of the K pixel circuits; a reference luminance setting circuit that sets, based on the variation coefficient, reference luminance for determining display luminance of each display element after degradation compensation; and a compensation computing circuit that compensates for degradation of the compensation-target circuit elements by correcting input video signals based on the reference luminance and the degree of degradation of each of the K pixel circuits, upon generating video signals to be supplied to the plurality of pixel circuits.