OLED Degradation Compensation Using Reference Pixel Brightness Ratios
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Solution Overview
Problem
Organic light emitting display devices face issues with maintaining uniform brightness due to OLED degradation over time, causing variations in light emission among pixels even when the same data signal is applied.
Innovation Solution
An organic light emitting display device incorporates a degradation compensator that determines the degree of degradation of pixels, selects a reference pixel based on operation modes (flat up or flat down), calculates coefficients for brightness modulation, and generates modulated data to adjust the brightness of pixels accordingly, ensuring uniformity by transforming the data into suitable voltages for storage and application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLEDs are used in display pixels, then the display device achieves fast response speed, low power consumption, and excellent brightness, but the OLEDs degrade over time causing brightness variation among pixels
Solution Approach 1:
The patent applies preliminary action by measuring the maximum emission brightness of each pixel in advance and storing this information. Based on these pre-measured values, compensation coefficients are calculated and stored before actual display operation. When displaying images, the pixel circuit uses these pre-calculated coefficients to compensate for degradation, thereby maintaining brightness uniformity without requiring real-time measurement or complex processing during operation.
2Reliability
If degradation compensation is implemented by measuring and calculating compensation coefficients for each pixel, then brightness uniformity is maintained, but the device complexity increases due to additional components and processing
Solution Approach 1:
The patent merges the degradation compensation function with the existing pixel circuit by integrating a compensation coefficient generator and a compensation coefficient storage unit directly into the pixel circuit. This allows the pixel circuit to not only receive display data but also generate and store its own compensation coefficients, eliminating the need for separate external compensation circuits and reducing overall system complexity.
Solution Approach 2:
The pixel circuit performs self-service by autonomously generating its own compensation coefficients based on its measured maximum emission brightness and autonomously storing these coefficients in its integrated storage unit. This self-contained approach eliminates the need for external control circuits to manage compensation, thereby simplifying the overall device architecture.
3Reliability
If compensation coefficients are calculated and stored for each pixel, then brightness degradation is compensated, but the storage area requirements and data processing increase
Solution Approach 1:
The patent applies local quality by calculating and storing compensation coefficients individually for each pixel based on its specific maximum emission brightness characteristics. Rather than using a global compensation value for the entire display, each pixel has its own tailored compensation coefficient, allowing precise local compensation while efficiently managing data storage requirements.
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 effectively maintains initial brightness levels by compensating for pixel degradation, ensuring consistent display quality by adjusting the brightness of pixels based on their degradation levels, thereby preventing significant brightness inconsistencies.
Implementation Method 1
Each OLED emits light from a corresponding pixel based on the recombination of electrons and holes in an emission layer
Data Source
AI summary
An organic light emitting display device includes a storage area, a degradation compensator, and a display driver. The storage area stores accumulated data for a plurality of pixels. The degradation compensator determines degrees of degradation of the pixels based on the accumulated data, selects a flat up mode or a flat down mode, selects a reference pixel based on the selected mode, generates ratios of a maximum emission brightness of the reference pixel to a maximum emission brightness of the pixels as first coefficients, and generates modulated data for the pixels using the first coefficients and margin ratios. The panel driver transforms the modulated data to data voltages for the pixels, adds the modulated data to the accumulated data, and stores the accumulated data in the storage area.