Electrowetting Display Driving Scheme for Reflectance Hysteresis
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Solution Overview
Problem
Electrowetting display pixels exhibit hysteresis in oil movement, leading to unpredictable reflectance and difficulties in controlling image quality due to the dependence of reflectance on the pixel's initial state, resulting in degradations in overall image quality and appearance.
Innovation Solution
Implementing a driving scheme that first sets the pixel to a known condition using a specific driving voltage, followed by predictable changes to achieve target reflectance, and utilizing dithering algorithms to avoid uncertain reflectance values, ensuring accurate and predictable reflectance control across groups of pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct voltage control is applied to electrowetting pixels, then the display can operate with simple driving circuitry, but the reflectance becomes unpredictable due to hysteresis in oil movement
Solution Approach 1:
The patent applies preliminary action by establishing a known initial state for each pixel before applying the driving voltage. The controller tracks the state of each pixel (whether oil is in left or right chamber) and uses this information to determine the appropriate voltage to achieve the desired reflectance. This preliminary state knowledge eliminates the unpredictability caused by hysteresis while maintaining relatively simple driving circuitry.
Solution Approach 2:
The patent implements feedback by continuously tracking the state of each pixel and using this information to adjust subsequent driving voltages. The controller maintains state information for each pixel and uses feedback from this state tracking to predict and control the reflectance outcome, thereby resolving the hysteresis issue without requiring complex circuitry.
2Device complexity
If hysteresis in oil movement is ignored, then the driving scheme can be simplified, but image quality degrades due to unpredictable reflectance values
Solution Approach 1:
The patent applies preliminary action by establishing a known initial state for each pixel before applying the driving voltage. The controller tracks the state of each pixel (whether oil is in left or right chamber) and uses this information to determine the appropriate voltage to achieve the desired reflectance. This preliminary state knowledge eliminates the unpredictability caused by hysteresis while maintaining relatively simple driving circuitry.
Solution Approach 2:
The patent changes the approach from directly controlling reflectance through voltage to controlling the system state through sequential voltage applications. By changing the driving parameters to include state tracking and predictive voltage selection based on current state, the patent achieves both simplicity and image quality.
3Manufacturing precision
If state-dependent driving is implemented to achieve predictable reflectance, then image quality improves, but the control system becomes more complex
Solution Approach 1:
The patent implements feedback by continuously tracking the state of each pixel and using this information to adjust subsequent driving voltages. The controller maintains state information for each pixel and uses feedback from this state tracking to predict and control the reflectance outcome, thereby resolving the hysteresis issue without requiring complex circuitry.
Solution Approach 2:
The system serves itself by using its own state information to make control decisions. The controller tracks the state of each pixel and uses this self-generated information to determine the appropriate driving voltage, eliminating the need for external sensing or complex control mechanisms.
4Measurement precision
If dithering algorithms are used to achieve target reflectance, then reflectance precision improves, but processing time increases
Solution Approach 1:
The patent applies preliminary action by establishing a known initial state for each pixel before applying the driving voltage. The controller tracks the state of each pixel (whether oil is in left or right chamber) and uses this information to determine the appropriate voltage to achieve the desired reflectance. This preliminary state knowledge eliminates the unpredictability caused by hysteresis while maintaining relatively simple driving circuitry.
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, enhances image quality by allowing precise control over pixel reflectance, and maintains the display's contrast ratio without negative impacts.
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 target reflectance value for a sub-pixel in the plurality of sub-pixels is determined. A reflectance value of the sub-pixel is set to the target reflectance value by setting the reflectance value of the sub-pixel to a first reflectance value greater than a threshold value, and setting the reflectance value of the sub-pixel to the target reflectance value.