Organic EL Display Pixel Brightness Non-Uniformity Correction
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Solution Overview
Problem
Organic EL display apparatuses face brightness non-uniformity due to variations in threshold voltage (Vth) and current-voltage (V-I) slope of drive transistors across pixels, leading to uneven light emission.
Innovation Solution
An organic EL display apparatus with a correction gain storage unit and correction unit that adjusts pixel brightness data based on pixel position-specific correction gains and offsets, compensating for the V-I characteristic slope of drive transistors to ensure uniform light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction of Vth alone is applied, then pixel-to-pixel variation of black level is corrected, but brightness non-uniformity due to V-I slope variation remains
Solution Approach 1:
The patent changes the correction parameter from only Vth (threshold voltage) to include both Vth and gm (transconductance/V-I slope). By measuring and storing correction values for both parameters across multiple pixels, and applying both corrections during display operation, the system achieves comprehensive compensation for transistor characteristic variations, resolving the brightness non-uniformity that remained when only Vth correction was applied.
2Reliability
If pixel-by-pixel measurement and correction is implemented, then brightness uniformity is improved, but device complexity and correction data storage requirements increase
Solution Approach 1:
The patent segments the correction approach by dividing pixels into groups (e.g., by row or column) and measuring/correcting characteristics for each group rather than requiring individual pixel measurement and storage. This allows correction data to be organized in a structured manner (separate correction data for different pixel groups), reducing the overall complexity of the correction system while maintaining brightness uniformity across all pixels.
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 compensates for variations in drive transistor characteristics, achieving even and appropriate light emission across all pixels, thereby addressing brightness non-uniformity issues.
Implementation Method 1
an organic EL element 3... the organic EL element 3 emitting light
Data Source
AI summary
An organic EL display apparatus including in each display pixel an organic EL element. A drive transistor supplies a drive current that depends on brightness data and having the display pixels arranged in a matrix form. The display includes a correction gain storage unit for storing display pixel positions and a correction gain for correcting the slope of the brightness-data-based drive current of the drive transistors in the display pixels; and a correction unit for correcting pixel-by-pixel brightness data depending on the pixel position using the correction gain stored in the correction gain storage unit into brightness data for the pixel to generate corrected brightness data, each of the display pixels is displayed by driving its drive transistor in response to the data generated by the correction gain storage unit and the correction unit and supplying the corresponding organic EL element with the drive current.