Bistable Display Driving Method Reducing Frame Count
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Solution Overview
Problem
Conventional bistable display devices require a high number of frames and a higher frame rate to switch images, especially when transitioning from high to low gray scales, due to the need for reset operations and complex voltage applications.
Innovation Solution
The method involves dividing the frame period into sub-frame periods, adjusting the ratio of sub-frame periods for different states, and applying specific voltages to maintain the light valve layer in the homeotropic state as the dark state, eliminating the need for reset operations by ensuring the light valve layer is in the planar state before displaying the next frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bistable display devices use reset operations to switch images from high to low gray scales, then the display can maintain stability, but the number of frames required increases and frame rate must be increased
Solution Approach 1:
The patent applies preliminary action by maintaining the light valve layer in the planar state during the entire frame period, including the second duration when no voltage is applied. This preliminary preparation ensures that the light valve layer is already in the correct state before the next frame begins, eliminating the need for reset operations and reducing the number of frames required.
Solution Approach 2:
The patent changes the voltage parameter application strategy by applying voltage only during the first duration to enter the homeotropic state, then maintaining the planar state during the second duration without voltage application. This parameter change approach allows the display to maintain stability while reducing frame count requirements.
2Reliability
If conventional bistable display devices perform reset operations to maintain planar state, then the display reliability is preserved, but the frame rate must be increased to achieve acceptable display performance
Solution Approach 1:
The patent ensures the light valve layer is maintained in the planar state throughout the entire frame period as a preliminary condition, so that when the next frame needs to be displayed, the light valve layer is already prepared in the correct state. This eliminates the need for additional reset operations and reduces the required frame rate.
Solution Approach 2:
The patent maintains the useful action of displaying images continuously without interruption for reset operations. By keeping the light valve layer in the planar state during the second duration when no voltage is applied, the display continues to show the image stable without needing to interrupt for reset, thereby maintaining productivity.
3Adaptability or versatility
If voltage is applied to maintain homeotropic state as dark state, then gray scale transitions are achieved, but complex voltage applications are required especially for high to low gray scale transitions
Solution Approach 1:
The patent segments the frame period into two distinct durations: first duration for applying voltage to enter homeotropic state, and second duration for maintaining planar state without voltage. This segmentation simplifies the voltage application pattern compared to continuous complex voltage sequences, while still achieving gray scale transitions.
Solution Approach 2:
Instead of continuously applying voltage to maintain the dark state and only reducing voltage for bright states, the patent inverts the approach by applying voltage only when needed to enter homeotropic state, then maintaining planar state during the second duration. This inversion simplifies the voltage control logic.
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 reduces the total number of frames required to display each image, minimizing the need for reset operations and achieving efficient gray scale transitions without increasing frame rate, thereby enhancing the display performance of bistable display devices.
Implementation Method 1
The cholesteric liquid crystal display device comprises characteristics of bistabiility, high contrast and high color saturation. The light valve layer CLCL comprises a plurality of liquid crystals CLC. The light L passes through the light valve layer CLCL via the first substrate S1, and is then absorbed by the light absorption layer LAL through the second substrate S2.
Implementation Method 2
In the planar state, the liquid crystals CLC in the light valve layer CLCL are aligned, which corresponds to highest reflectivity. In the focal conic state, the liquid crystals CLC in the light valve layer CLCL are arranged orderlessly, which scatters the injected light L.
Implementation Method 3
the black substance absorbs light to display the dark state, or the colored substance absorbs light to display a colored state
Implementation Method 4
The state of the light valve layer of the cholesteric liquid crystal display device can be altered according to an electrical field applied to the light valve layer. The light valve layer can be transformed to the focal conic state from the planar state by applying a relatively smaller electrical field
Data Source
AI summary
A driving method for a bistable display device includes setting a first duration and a second duration according to a frame period; applying a first voltage to a light valve layer in the first duration according to display data, so as to transform the light valve layer from a first state to a second state; and applying a second voltage in the second duration to the light valve layer in the second duration for the light valve layer to transform to the first state. Since the light valve layer of the bistable display device is already at the first state prior to displaying the next image, the light valve layer is not required to reset when switching displayed images, hence reducing the total number of frames required to display each image.