OLED Luminance Compensation via Pixel Sensing and Digital Adjustment
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Solution Overview
Problem
Conventional organic light emitting displays experience degradation over time, leading to inconsistent luminance due to changes in temperature and resistance, affecting the display's ability to maintain desired image brightness.
Innovation Solution
An organic light emitting display system that includes a sensing unit, data driver, and timing controller to extract degradation information from organic light emitting diodes, converting it into digital signals to adjust the voltage applied to the diodes, ensuring consistent luminance by compensating for degradation through a method involving multiple transistors and capacitors in the pixel circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic light emitting displays are used without degradation compensation, then the display structure remains simple and manufacturing cost is low, but the luminance becomes inconsistent over time due to OLED degradation
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a sensing unit that measures OLED characteristics, a compensation unit that calculates correction values, and a driving unit that applies compensated signals. This segmentation allows degradation compensation functionality to be added without completely redesigning the pixel circuit, thereby improving luminance consistency while managing complexity through modular architecture.
Solution Approach 2:
The sensing unit performs preliminary measurement of OLED characteristics (such as voltage at constant current) before the actual display operation. Based on these preliminary measurements, compensation values are calculated and stored, so that when degradation occurs, the pre-established compensation mechanism can immediately adjust the driving signals to maintain consistent luminance.
2Illumination intensity
If degradation compensation mechanisms are added to maintain luminance, then luminance uniformity improves, but the manufacturing cost and device complexity increase
Solution Approach 1:
The sensing unit and compensation unit are designed to serve multiple functions: they not only compensate for OLED degradation but also characterize OLED performance, monitor display quality, and provide data for lifetime prediction. This multi-functionality reduces the need for separate dedicated compensation circuits, thereby improving luminance uniformity while minimizing the increase in manufacturing complexity.
Solution Approach 2:
The display system performs self-diagnosis and self-compensation by using its own sensing units to measure OLED characteristics and automatically adjusting driving signals through integrated compensation algorithms. This self-service approach eliminates the need for external calibration equipment and manual adjustment mechanisms, improving luminance uniformity while keeping manufacturing processes straightforward.
3Measurement precision
If sensing units and compensation circuits are integrated into each pixel, then degradation compensation accuracy is improved, but the pixel area and device complexity increase
Solution Approach 1:
The sensing unit is integrated within the pixel circuit structure, sharing transistors and capacitors with the driving function. The same transistor that drives the OLED also serves as the sensing transistor during measurement periods. This merging allows high-precision degradation detection without requiring separate dedicated sensing transistors, thereby improving measurement precision while minimizing pixel area increase.
Solution Approach 2:
The sensing operation is performed periodically at specific time intervals (such as during blanking periods or at fixed refresh intervals) rather than continuously. This periodic sensing allows the pixel circuit to switch between measurement and display modes, enabling accurate degradation detection while keeping the pixel circuit simple and minimizing the impact on pixel area.
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 maintains uniform luminance across the display by compensating for organic light emitting diode degradation, ensuring consistent image brightness regardless of temperature and resistance changes, thereby improving the display's overall performance.
Implementation Method 1
the organic light emitting displays make use of organic light emitting diodes that emit light by re-combination of electrons and holes
Data Source
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AI summary
An organic light emitting display includes: a sensing unit (170) for extracting degradation information of an organic light emitting diode included in each of the pixels, and for transferring a first digital value and a second digital value corresponding to the extracted degradation information to a data driver; the data driver (120) for generating data signals corresponding to second data supplied from a timing controller during a normal driving period; a first analog-digital converter (180) for converting the voltage corresponding to the first digital value to a fourth digital value, and for converting the voltage corresponding to the second digital value to a fifth digital value; and the timing controller (150) for storing the fourth digital value and the fifth digital value, and for changing first data supplied from an exterior in accordance with the fourth digital value and the fifth digital value to generate the second data.