Electrowetting Display Pixel Driving Scheme for Reflectance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrowetting display pixels exhibit hysteresis in oil movement, making it difficult to accurately predict and control reflectance, leading to degradations in image quality and image artifacts due to unpredictable changes in light transmission based on the pixel's initial state.
Innovation Solution
Implementing a driving scheme that first sets the pixel to a known condition using a specific driving voltage, and then adjusts the voltage to achieve predictable changes in reflectance, along with the use of dithering algorithms to avoid setting reflectance values that are difficult to predict, ensuring target reflectance levels are achieved across groups of pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple voltage-driven approach is used to control pixel reflectance, then the device complexity is reduced, but the measurement precision of reflectance becomes unpredictable due to hysteresis effects
Solution Approach 1:
The patent applies preliminary action by establishing a known initial state for each pixel before applying the reflectance control voltage. The system determines whether each pixel is currently in an open or closed state, and based on this preliminary knowledge, selects appropriate driving voltages from different voltage sets. This preliminary state determination resolves the hysteresis problem by ensuring we start from a known condition, thereby improving reflectance prediction accuracy without significantly increasing device complexity.
Solution Approach 2:
The patent implements parameter changes by using multiple voltage sets instead of a single voltage range. Different voltage sets are applied depending on the initial state of the pixel (open or closed). This parameter differentiation allows the system to achieve predictable reflectance values by selecting the appropriate voltage set based on the current state, thereby resolving the contradiction between simple driving schemes and accurate reflectance control.
2Manufacturing precision
If dithering algorithms are applied to avoid unpredictable reflectance values, then the manufacturing precision of reflectance control is improved, but the productivity of display updates is reduced
Solution Approach 1:
The system performs preliminary determination of pixel states before display update, organizing pixels into groups based on their open/closed status. This preliminary organization allows subsequent reflectance control to proceed efficiently with pre-determined voltage selections, minimizing the computational overhead of dithering algorithms while maintaining precision.
Solution Approach 2:
The patent segments the pixel population into different groups based on their initial states (open or closed). This segmentation allows the system to apply different voltage sets to different segments, improving reflectance control precision. The segmentation approach also optimizes productivity by enabling parallel processing of different pixel groups and reducing the computational complexity of individual pixel control.
3Reliability
If the pixel state is determined and driven to a known condition before setting reflectance, then the reliability of reflectance control is improved, but the loss of time in addressing cycles increases
Solution Approach 1:
The system performs preliminary state determination of pixels at the beginning of addressing cycles, establishing known initial conditions before reflectance control. This preliminary action improves reliability by ensuring predictable starting states. The patent optimizes time loss by performing this determination efficiently and using the state information throughout the entire addressing cycle, rather than requiring repeated state checks.
Solution Approach 2:
The patent maintains continuity of useful action by using the determined pixel states throughout the entire addressing cycle. Once pixels are segmented into groups based on their initial states, this segmentation information is continuously utilized for voltage selection and reflectance control across multiple display updates, eliminating the need for repeated state determination and reducing time loss in subsequent cycles.
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 minimizes reflectance uncertainty, allowing for precise control of pixel reflectance and improved image quality by ensuring predictable reflectance settings, even in the presence of hysteresis effects, without negatively affecting the display's contrast ratio.
Implementation Method 1
An electrowetting display includes an array of pixels individually bordered by pixel walls that retain liquid, such as an opaque oil, for example. Light transmission through each pixel is adjustable by electronically controlling a position of the liquid in the pixel.
Data Source
AI summary
A system and method of driving an electrowetting display device including a plurality of sub-pixels are presented. A sub-pixel in the plurality of sub-pixels is determined to be in an open state or a closed state and a target reflectance value is determined for the sub-pixel. For the sub-pixel in the open state, the target reflectance value is determined to be less than a first threshold value, and a reflectance value of the sub-pixel is set to either a minimum reflectance value or the first threshold value. For the sub-pixel in the closed state, the target reflectance value is determined to be less than a second threshold value, and the reflectance of the sub-pixel is set to either the minimum reflectance value or the second threshold value.