AMOLED Luminance Uniformity Compensation via Digital Lookup Tables
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Solution Overview
Problem
Active-matrix organic light-emitting diode (AMOLED) displays experience non-uniform luminance due to degradation over time, caused by inefficiencies in thin film transistors (TFTs) and organic light-emitting diodes (OLEDs), leading to reduced image quality as pixels degrade at different rates.
Innovation Solution
A compensation system adjusts the digital inputs to pixel circuits based on measured or estimated degradation, using a compression factor to maintain uniform luminosity by incrementing digital signals and redistributing the remaining range to compensate for degraded pixels, without the need for costly light detectors integrated into each pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light detectors are integrated into each pixel to measure and compensate for degradation, then luminance uniformity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses a lookup table that stores pre-measured compensation values for different pixel locations and aging times. Instead of integrating light detectors into each pixel, the system creates a digital copy (lookup table) of the degradation characteristics and uses this copy to compensate for luminance non-uniformity, thereby avoiding the complexity and cost of physical light detectors in each pixel
Solution Approach 2:
The patent replaces the mechanical/optical system of integrated light detectors with an electronic/software-based solution. A controller executes algorithms that use stored compensation data to adjust pixel drive signals, substituting physical measurement hardware with computational methods to achieve the same luminance uniformity compensation
2Illumination intensity
If digital input range is compressed to allow compensation for degraded pixels, then luminance uniformity is improved, but the maximum brightness capability is reduced
Solution Approach 1:
The patent applies compression only to the portion of the digital input range that is needed for compensation, rather than compressing the entire range. The lookup table stores compensation values that are added to the compressed input, allowing the system to recover the effective brightness capability while still providing uniformity compensation across all pixels
Solution Approach 2:
The patent dynamically adjusts the compression factor and offset values based on the pixel's location, aging characteristics, and desired luminance uniformity. By changing these parameters adaptively rather than using fixed compression, the system can maintain maximum brightness capability for pixels that need it while providing compensation for degraded pixels
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures consistent luminance across the display by dynamically adjusting digital inputs, maintaining image quality and extending the lifespan of AMOLED displays by compensating for differential aging of pixels, thereby reducing power consumption and maintaining uniformity.
Implementation Method 1
The OLED 30 converts the current 28 into visible light 36
Data Source
AI summary
A display degradation compensation system and method for adjusting the operating conditions for pixels in an OLED display to compensate for non-uniformity or aging of the display. The system or method sets an initial value for at least one of peak luminance and an operating condition, calculates compensation values for the pixels in the display, determines the number of pixels having compensation values larger than a predetermined threshold compensation value, and if the determined number of pixels having compensation values larger than said predetermined threshold value is greater than a predetermined threshold number, adjusts the set value until said determined number of pixels is less than said predetermined threshold number.