OLED White Chromaticity Compensation via Gain Adjustment
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Solution Overview
Problem
Conventional organic light emitting diode (OLED) displays using white OLEDs face challenges in maintaining uniform white chromaticity coordinates across different gray levels due to variations in driving voltage, leading to color balance shifts and a yellowish phenomenon at low gray levels.
Innovation Solution
An OLED display system that includes a data operation unit to extract a representative value from primary color data, a gain adjusting unit to generate a gain value for compensating white chromaticity coordinates, and a data conversion unit to produce color compensation data, ensuring white chromaticity coordinates align with target values by adjusting gain values for each gray level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If white OLED is used to generate white light through combination of emission layers, then device complexity is reduced and ease of manufacture is improved, but chromaticity coordinates shift at different gray levels causing color balance deterioration
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in a lookup table before actual display operation. The compensation values are computed based on measured chromaticity deviations at different gray levels, and these pre-computed values are then used to adjust input signals in real-time, preventing chromaticity shifts before they occur.
Solution Approach 2:
The patent implements feedback by measuring the actual chromaticity coordinates of the white OLED at different gray levels, comparing them against target values, and using the deviation information to generate compensation values. This closed-loop approach continuously corrects for material-specific variations in driving characteristics.
2Device complexity
If conventional deposition method using metal mask is used, then manufacturing process is simplified, but manufacturing precision deteriorates due to mask bending in large area substrates
Solution Approach 1:
The patent applies segmentation by dividing the emission layer formation process into multiple sequential deposition steps. Instead of attempting to deposit all emission layers simultaneously through a single large mask, the process is broken down into separate deposition operations, each handling specific layers or regions, thereby maintaining precision across large substrate areas.
Solution Approach 2:
The patent transitions from a planar mask-based deposition approach to a multi-layer sequential deposition method. By adding the dimension of time and process sequencing, the system achieves precise patterning across large areas without relying on a single large mask, effectively moving from a 2D mask problem to a 3D process solution.
3Measurement precision
If gain adjusting unit multiplies preset gain value by white data, then chromaticity coordinate compensation is achieved, but device complexity increases
Solution Approach 1:
The patent applies copying by using a lookup table that stores pre-computed compensation values derived from chromaticity measurements. Instead of implementing complex real-time calculation circuits, the system copies pre-determined correction values from the lookup table based on the current gray level, achieving precise chromaticity compensation through simple memory access and multiplication operations.
Data Source
AI summary
An organic light emitting diode display comprises a display panel, a data operation unit, a gain adjusting unit, and a data conversion unit. The display panel comprises an R sub-pixel, a G sub-pixel, a B sub-pixel, and a W sub-pixel. The data operation unit generates a data operation value. The gain adjusting unit generates a gain adjusting value of the three primary color data. The data conversion unit generates four color compensation data, whose white chromaticity coordinates are compensated for each pixel.