Electrophoretic Display Partial Updates for Color Drift Correction
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Solution Overview
Problem
Electrophoretic displays suffer from color shifts and ghosting due to partial updates, which can be displeasing to users and affect image quality, particularly in multi-particle systems with complex color gamuts.
Innovation Solution
A method is introduced to reduce color drift by applying update waveforms specifically to identified matrices of pixels that remain in a first optical state after a partial update, using shorter waveforms for the first optical state and avoiding updates for other pixels, thereby minimizing unintended color transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If partial updates are performed to save power and reduce update time, then energy consumption and update time are reduced, but color drift and ghosting occur between updated and non-updated regions
Solution Approach 1:
The patent segments the display update process by identifying specific regions (M×N matrices) that require color drift correction. Instead of updating the entire display, only segmented regions with persistent color drift are targeted with correction waveforms, while other regions remain unchanged. This selective segmentation resolves the contradiction by maintaining color accuracy in critical areas without sacrificing the power-saving benefits of partial updates.
Solution Approach 2:
The patent applies different update strategies to different regions of the display based on their specific needs. Regions identified as having color drift (M×N matrices) receive correction waveforms, while other regions without color drift receive no update. This local differentiation allows the system to maintain color accuracy where needed while minimizing unnecessary updates elsewhere, thus resolving the contradiction between color accuracy and update efficiency.
2Manufacturing precision
If full screen updates are performed to remove color drift and ghosts, then color accuracy is improved, but energy consumption and update time increase significantly
Solution Approach 1:
The patent applies partial action by performing color drift correction only on specific M×N matrix regions that exhibit color drift, rather than updating the entire display screen. This selective partial updating consumes significantly less energy than a full screen update while still achieving the color accuracy benefits where needed. The principle resolves the contradiction by providing just enough correction action to eliminate color drift without the excessive energy cost of a complete screen refresh.
Solution Approach 2:
The system automatically identifies regions with color drift and applies correction waveforms only where necessary, making the correction process self-regulating and efficient. This self-service approach eliminates the need for manual full-screen updates by users, automatically maintaining color accuracy while minimizing power consumption through targeted rather than universal correction.
3Manufacturing precision
If update waveforms are applied to all pixels to maintain color accuracy, then color drift is reduced, but the complexity of the update process and computational overhead increase
Solution Approach 1:
The patent simplifies the update process by segmenting it into two distinct phases: identification of M×N matrices requiring correction, and application of correction waveforms only to those specific segments. This segmentation reduces computational overhead compared to processing all pixels uniformly, as the system only performs complex waveform operations on identified problem regions rather than the entire display.
Solution Approach 2:
The patent performs preliminary identification of M×N matrices that require color drift correction before applying update waveforms. This preliminary action allows the system to pre-determine which regions need correction, simplifying the subsequent update process by avoiding unnecessary waveform applications to regions that don't require correction, thus reducing overall computational complexity.
4Use of energy by stationary object
If no update waveform is sent to pixels remaining in the first optical state, then power consumption is minimized and unintended color transitions are avoided, but color drift may occur in those pixels over time
Solution Approach 1:
The patent applies local quality by differentiating between two types of pixels: those in M×N matrices that receive correction waveforms to prevent color drift, and those outside M×N matrices that receive no update to minimize power consumption. This local differentiation allows the system to optimize the trade-off between power savings and color accuracy on a pixel-by-pixel basis, applying corrections only where color drift is identified as a problem.
Solution Approach 2:
The system uses a self-service approach where pixels that are not part of identified M×N matrices automatically maintain their current state without receiving update waveforms, thereby consuming minimal power. The system only intervenes with correction waveforms in specific regions where color drift has been detected, allowing other regions to self-maintain without energy expenditure.
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
This approach effectively reduces color drift and ghosting, ensuring accurate color representation and maintaining image quality during partial updates, even in complex multi-particle electrophoretic displays.
Implementation Method 1
An electrophoretic display (EPD) changes color by modifying the position of a charged colored particle with respect to a light-transmissive viewing surface
Implementation Method 2
sending an update waveform for the first optical state to each pixel of the M×N matrix of pixels
Data Source
AI summary
Methods for using “P” type waveforms to reduce color drift, ghosting, and other transient color shifts. While the method is most useful for regulating white state drift, related techniques can be used to address color state drift in other multi-particle color platforms, as well as in color-filter-array (CFA) electrophoretic displays. The methods help to fix color drift that may accompany partial update methods, i.e., whereby only a portion of the display panel receives update instructions from the controller between a first and a second image.