OLED Display Compensation for Luminance Uniformity
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Solution Overview
Problem
Conventional organic light emitting displays face issues with non-uniform luminance due to deterioration of organic light emitting diodes and variations in threshold voltage/mobility among driving transistors, leading to reduced image quality over time.
Innovation Solution
An organic light emitting display system that includes a sensing unit to detect and compensate for deterioration of organic light emitting diodes and threshold voltage/mobility variations among driving transistors, using a switching unit to selectively couple pixels with a current sink or source, and a timing controller to adjust data signals based on sensed voltages, ensuring uniform luminance across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pixel circuits without sensing units are used, then device complexity is reduced, but luminance uniformity deteriorates due to OLED deterioration and transistor parameter variations
Solution Approach 1:
The pixel circuit is segmented into multiple functional blocks: a sensing unit with current source/sink for measuring transistor parameters, a storage unit for storing threshold voltage and mobility data, and a driving unit for compensation. This segmentation allows the circuit to individually measure and compensate for each transistor's characteristics, achieving luminance uniformity while managing complexity through modular design.
Solution Approach 2:
The sensing unit measures the actual threshold voltage and mobility of each transistor, and this measured data is fed back to adjust the driving current. The feedback mechanism continuously compensates for transistor parameter variations and OLED deterioration, maintaining accurate luminance control despite component aging and manufacturing variations.
2Device complexity
If no compensation for OLED deterioration is implemented, then device complexity remains low, but luminance output deteriorates over time
Solution Approach 1:
The sensing unit performs preliminary measurement of transistor parameters (threshold voltage and mobility) before the OLED deteriorates significantly. This advance measurement allows the system to establish baseline compensation values that can be used to correct for future deterioration, maintaining luminance output over the display's operational lifetime.
Solution Approach 2:
The system changes the operating parameters of the pixel circuit based on measured transistor characteristics. By adjusting the driving current according to the stored threshold voltage and mobility data, the system compensates for OLED efficiency changes and maintains consistent luminance output despite component aging.
3Device complexity
If transistor parameter variations are not compensated, then device complexity is minimized, but image quality deteriorates due to non-uniform luminance
Solution Approach 1:
Each pixel circuit is equipped with its own sensing unit that measures the local characteristics of its specific transistor. This local measurement approach accounts for spatial variations in transistor parameters across the display, allowing each pixel to be individually compensated for its unique characteristics, thereby achieving uniform luminance across the entire display.
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
The system effectively compensates for diode deterioration and transistor mobility variations, maintaining consistent image luminance and improving overall display quality by adjusting data signals in real-time.
Implementation Method 1
An organic light emitting display displays an image using organic light emitting diodes that generate light through recombination of electrons and holes
Data Source
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AI summary
An organic light emitting display includes: scan lines for applying scan signals; control lines for applying control signals; and data lines for applying data signals. The organic light emitting display further includes: pixels coupled to the scan, control and data lines for displaying an image; power supply lines coupled to the pixels; and a data driver for supplying the data signals of the image to the data lines. The organic light emitting display also includes: a power supply driver for swinging a voltage at the power supply lines between a first level and a second level; a sensing unit including a current sink for sinking a first current from the pixels and a current source for supplying a second current to the pixels; and a switching unit for selectively electrically coupling the pixels to at least one of the data driver, the current source or the current sink.