Electrophoretic Display Driving Method for Ghost Image Reduction
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Solution Overview
Problem
Conventional methods of driving electrophoretic displays result in user discomfort due to ghost images and extreme black-and-white twinkling effects during frame switching, caused by the viscous dielectric solvent limiting the movement speed of charged pigment particles.
Innovation Solution
A method of driving electro-optic displays that involves displaying a first frame, determining the data for a second frame, displaying an eliminating frame at an intermediate gray level between the first and second frames, and then gradually transitioning to the second frame through a series of medium frames, ensuring the gray level at the transition time is close to the intended second frame level, thereby reducing the extreme twinkle effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the conventional method displays frames directly by moving charged pigment particles in viscous dielectric solvent, then the display structure is simple, but ghost images appear due to limited particle movement speed
Solution Approach 1:
The patent applies preliminary action by displaying an eliminating frame before the target frame to proactively remove residual image effects. The eliminating frame is calculated to counteract the ghost image formed by slow particle movement, thereby preventing the ghost image from appearing in the final display rather than trying to remove it afterward.
Solution Approach 2:
The patent introduces medium frames as intermediary elements between the eliminating frame and the target frame. These medium frames serve as transition states that gradually adjust the pigment particle distribution, acting as a mediator to smooth out the abrupt changes and reduce visual artifacts during the frame transition process.
2Illumination intensity
If the conventional method uses extreme black and white frames for switching, then the display contrast is high, but users experience uncomfortable extreme black-and-white twinkling effects
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gray level parameters of display frames. Instead of using fixed extreme black and white values, the system calculates intermediate gray levels for eliminating and medium frames based on the previous and target frames, thereby changing the brightness parameter progressively to avoid abrupt visual transitions while maintaining display contrast.
Solution Approach 2:
The patent uses preliminary action by preparing eliminating frames with calculated intermediate gray levels before displaying the target frame. This preliminary adjustment of brightness parameters prevents the sudden extreme black-and-white transitions that cause user discomfort, while still achieving the desired high contrast effect in the final display.
3Speed
If the dielectric solvent viscosity is reduced to increase particle movement speed, then frame switching speed improves, but the electrophoretic fluid stability deteriorates
Solution Approach 1:
The patent applies preliminary action by calculating and displaying eliminating frames before the target frame to proactively compensate for the slow particle movement caused by high viscosity. This allows the system to work with the inherent slow response of the electrophoretic fluid rather than trying to overcome it, maintaining fluid stability while improving effective frame switching speed through predictive frame generation.
Solution Approach 2:
The patent applies parameter changes by adjusting the timing and gray level parameters of displayed frames to match the slow response characteristics of the viscous electrophoretic fluid. The system modifies display parameters (frame sequence, gray levels, timing) to optimize performance within the constraints of high-viscosity fluid dynamics, rather than changing the fluid's physical properties.
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 significantly reduces user discomfort associated with frame switching by minimizing the visibility of ghost images and extreme gray level changes, providing a smoother transition between frames.
Implementation Method 1
the electrophoretic fluid 124 filling in each of the microcapsules 122 includes the dielectric solvent 124a and a plurality of charged pigment particles 124b dispersed in the dielectric solvent 124a. When the electrophoretic display 100 displays the first frame F11 or the second frame F12, part of the charged pigment particles 124b in each of the microcapsules 122 move to a side of the electrophoretic display 100
Data Source
AI summary
A method of driving an electro-optic display includes the following steps. First, a first frame is displayed on pixels at a first time. Next, data of a second frame predetermined to be displayed on the pixels at a second time later than the first time is determined. Next, an eliminating frame showing a first extreme gray level or a second extreme gray level is displayed on the pixels at a third time. Afterwards, a medium frame is displayed on the pixels at a fourth time later than the third time. The third and fourth times are between the first and second times. The gray level shown by each pixel at the fourth time is close to the gray level predetermined to be shown by the same pixel at the second time. Thereafter, the second frame is displayed on the pixels at the second time.