Parallel Pixel State Detection for OLED Brightness and Contrast
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Solution Overview
Problem
In self-emissive display devices like OLEDs, the internal resistance of light emitting elements increases over time, leading to reduced current flow and potential pixel burn-in, making it difficult to detect and correct pixel states efficiently during the blanking period without affecting light emission brightness or contrast.
Innovation Solution
A parallel detection system is implemented, dividing pixels into groups for simultaneous state detection in both horizontal and vertical directions, using separate power supplies and current sources to detect pixel states during the blanking period, and correcting variations between groups to maintain continuity and reduce detection time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a certain current is applied to the pixel during the blanking period for detection, then the pixel state can be detected, but the detection time is elongated due to high capacitances and internal resistance
Solution Approach 1:
The patent divides the detection process into two distinct phases: a first detection period during the blanking period where a first current is applied and a first voltage is detected, and a second detection period where a second current is applied and a second voltage is detected. This segmentation allows the system to overcome the limitation of slow detection caused by high capacitances and internal resistance by using two different measurement approaches rather than relying on a single lengthy measurement process.
Solution Approach 2:
The patent implements periodic detection by applying currents and detecting voltages at specific periodic intervals within the blanking period. The first detection occurs during a first period, and the second detection occurs during a second period, allowing the system to gather multiple measurement points efficiently. This periodic approach enables faster overall detection compared to continuous measurement while still capturing the necessary pixel state information.
2Speed
If a large amount of current is applied to the pixel during detection, then the detection speed increases, but the light emission brightness increases and contrast is reduced
Solution Approach 1:
The patent dynamically adjusts the current level based on the detection phase. During the first detection period, a first current is applied, and during the second detection period, a second current is applied. This dynamic current adjustment allows the system to optimize detection speed at different stages without causing excessive light emission that would reduce contrast, as the current is controlled and varied according to the specific detection requirements of each phase.
Solution Approach 2:
The patent performs preliminary detection during the blanking period before the display period begins. By detecting pixel states in advance during the first and second periods of the blanking period, the system obtains necessary measurement data without applying large currents during the actual light emission phase. This preliminary action ensures that detection is completed before contrast-critical display periods, maintaining image quality while enabling fast detection.
3Measurement precision
If the blanking period is used for detection, then no voltage is applied to the pixel for light emission, but the amount of current to be applied is limited
Solution Approach 1:
The patent changes the electrical parameters (current level and detection timing) to optimize the detection process during the blanking period. By applying a first current during the first period and a second current during the second period, the system adapts the current parameters to match the available time window and electrical characteristics of the pixel, enabling effective detection within the constraints of the blanking period without requiring excessive current that would be unavailable or harmful.
Data Source
AI summary
An image display device comprises a unit which divides one line into a plurality of blocks (blocks A, B, and C) in a horizontal direction and detects in parallel, a unit which collectively detects a plurality of lines (lines A and B) in a vertical direction in parallel. The unit detects a pixel state of a pixel of the block (for example, block A) and a pixel state of the same pixel as an adjacent block (for example, block B), and corrects a variation between the detection result of the block and the detection result of the adjacent block. The unit detects a pixel state of a pixel through the line (for example, line A) and a pixel state of the same pixel through a different line (for example, line B), and corrects a variation between the detection result of the line and the detection result of the different line.