Amorphous Silicon TFT EL Display Brightness Uniformity Correction
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Solution Overview
Problem
Active-matrix electroluminescent displays employing amorphous silicon thin-film transistors face issues with brightness variations and voltage threshold shifts, leading to decreased dynamic range and image artifacts, due to non-uniformity and low mobility of amorphous silicon TFTs, which existing methods struggle to address effectively.
Innovation Solution
A method is introduced to reduce brightness uniformity variations by dividing light-emitting elements into groups, selecting representative elements, measuring total currents, and deriving correction values to compensate image signals, thereby maintaining consistent brightness and improving display uniformity and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon thin-film transistors are used in active-matrix EL displays, then manufacturing cost is reduced and large-format displays can be produced, but brightness uniformity deteriorates due to spatial variation in TFT characteristics
Solution Approach 1:
The display is divided into multiple blocks, with each block containing multiple pixels. Representative pixels are selected from each block to measure current characteristics. This segmentation allows the patent to reduce the number of measurements needed while still achieving uniformity correction across the entire display, resolving the contradiction between manufacturing simplicity and brightness uniformity.
Solution Approach 2:
The patent uses representative pixels as copies of the actual pixels they represent. By measuring the current characteristics of these representative pixels and applying the correction factors to all pixels in their respective blocks, the patent achieves uniformity correction without needing to measure every individual pixel, thus maintaining ease of manufacture while improving brightness uniformity.
2Manufacturing precision
If individual pixel current measurement is performed for all light-emitting elements, then brightness uniformity is improved through accurate correction, but measurement time and device complexity increase
Solution Approach 1:
The patent segments the display into blocks with representative pixels, reducing the total number of measurements required. This segmentation strategy maintains brightness uniformity correction accuracy while significantly reducing measurement time compared to measuring every individual pixel.
Solution Approach 2:
Instead of measuring all pixels (excessive action), the patent measures only representative pixels from each block (partial action). This partial measurement approach is sufficient to achieve the desired brightness uniformity correction while reducing measurement time and complexity.
3Productivity
If representative pixels are measured to reduce measurement time, then productivity is improved, but measurement precision may deteriorate due to sampling error
Solution Approach 1:
The display is segmented into blocks with strategically selected representative pixels. This segmentation ensures that the representative pixels adequately reflect the characteristics of all pixels in their blocks, maintaining measurement precision while improving productivity by reducing the total number of measurements required.
Solution Approach 2:
The patent applies local quality by selecting representative pixels that are representative of their respective blocks' characteristics. Each representative pixel is chosen to accurately reflect the current characteristics of its block, ensuring that measurements taken from these representative pixels maintain high precision for correcting brightness uniformity across the entire display.
Data Source
AI summary
A method for reducing brightness uniformity variations in an active-matrix electroluminescent (EL) display employing amorphous silicon thin-film transistors, by providing an active-matrix EL display having amorphous silicon thin-film transistors; and deriving a first correction value from a measured or estimated value of light-emitting element performance. Subsequently groups of light-emitting elements are identified, whereupon one or more representative light-emitting elements are selected. Remaining steps include measuring total representative current used by the representative light-emitting elements for each predetermined group of light-emitting element; deriving an estimated second correction value from the first correction value, or the measured or estimated value of light-emitting element performance, and the measured total representative currents for each individual light-emitting elements; and employing the estimated second correction value to correct image signals for the changes in the output of the light-emitting elements and produce compensated image signals.