OLED Pixel Array Compensation for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting display devices face challenges in maintaining uniform luminance due to variations in threshold voltage/mobility of driving transistors and efficiency changes caused by degradation of organic light emitting diodes, leading to non-uniform image display.
Innovation Solution
A pixel array and organic light emitting display device design that includes a pixel circuit with transistors and a storage capacitor, a sensing unit for monitoring transistor mobility and OLED degradation, and a control block to adjust data signals based on sensed information, ensuring uniform luminance by compensating for variations and efficiency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional pixel circuit is used without compensation mechanisms, then the device structure remains simple, but luminance uniformity deteriorates due to transistor threshold voltage variations and OLED degradation
Solution Approach 1:
The patent implements sensing units that measure transistor threshold voltages and OLED characteristics before the actual display operation. Storage capacitors pre-store compensation values based on these measurements, enabling the pixel circuit to compensate for variations and degradation from the very first operation without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The patent establishes a feedback loop where sensing units continuously monitor transistor and OLED status, and the pixel circuit adjusts drive signals based on sensed threshold voltage variations and degradation levels. This feedback mechanism enables dynamic compensation that maintains luminance uniformity despite component variations and aging.
2Reliability
If sensing units and compensation circuits are added to each pixel, then luminance uniformity improves through compensation, but the pixel circuit complexity and manufacturing difficulty increase
Solution Approach 1:
The patent designs sensing units and pixel circuits that serve multiple functions: during normal operation, they display image data, and during sensing periods, they measure threshold voltages and OLED characteristics. This multi-functionality reduces the need for separate dedicated sensing circuits, thereby simplifying manufacturing while maintaining compensation capabilities.
Solution Approach 2:
The patent combines the sensing function and display function within the same pixel circuit structure. The data lines and pixel circuits are used for both displaying images and sensing transistor/OLED characteristics, eliminating the need for separate sensing pathways and reducing overall circuit complexity.
3Duration of action of stationary object
If real-time compensation for OLED degradation is implemented, then long-term image quality is maintained, but the processing complexity and power consumption increase
Solution Approach 1:
The patent implements degradation sensing and compensation at periodic intervals rather than continuously. The sensing unit measures OLED characteristics at specific times, and compensation values are updated periodically, reducing the processing load and power consumption compared to continuous real-time monitoring while still maintaining long-term image quality.
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 solution enables the display of images with uniform luminance by accurately compensating for transistor mobility and OLED degradation, thereby maintaining consistent image quality over time.
Implementation Method 1
the organic light emitting display device displays images using organic light emitting diodes (OLEDs) that emit light through recombination of electrons and holes
Data Source
AI summary
A pixel array and an organic light emitting display device including the same, can display an image with uniform luminance by compensating for a variation in threshold voltage/mobility of a driving transistor for each pixel and compensating for a change in efficiency due to degradation of an organic light emitting diode. A first pixel among the pixel array includes an organic light emitting diode; a pixel circuit positioned among an anode electrode of the organic light emitting diode, a first scan line and a first data line through which a data signal is supplied to the first pixel, and controlling current flowing in the organic light emitting diode; and a switching element controlling the coupling between a second data line through which a data signal is supplied to a second pixel of the plurality of pixels and the anode electrode of the organic light emitting diode.