Privacy Display Control with Switchable Liquid Crystal Retarder
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Solution Overview
Problem
Existing privacy displays face issues such as high luminance loss for head-on illumination and Moiré artefacts due to micro-louvres, and user-dependent control mechanisms that are not reliably activated, leading to inconsistent privacy modes.
Innovation Solution
A privacy display apparatus with a control system that selectively operates in public or privacy modes based on ambient light levels, using switchable backlights and liquid crystal retarders to manage off-axis luminance and reflectivity, ensuring high visibility for on-axis users while reducing image visibility for off-axis viewers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If micro-louvre optical films are used to provide privacy function, then off-axis visibility is reduced, but head-on luminance is significantly lost
Solution Approach 1:
The patent employs switchable liquid crystal layers that can dynamically change their optical properties between different states. In the privacy mode, the liquid crystal layer modulates light to reduce off-axis visibility while maintaining head-on luminance. This dynamic switching capability allows the display to adapt to different viewing conditions without permanent optical losses.
Solution Approach 2:
The invention changes the optical parameters of the liquid crystal layer by applying different voltages to achieve different viewing angle characteristics. By controlling the liquid crystal orientation through voltage application, the system can switch between a state that allows broad viewing (public mode) and a state that restricts off-axis viewing (privacy mode), thereby adjusting the trade-off between head-on luminance and off-axis visibility dynamically.
2Object-affected harmful factors
If micro-louvre films are used for privacy control, then off-axis visibility is reduced, but Moiré artefacts occur due to beating with pixels
Solution Approach 1:
The patent replaces the mechanical micro-louvre structure with an electrically controllable liquid crystal layer. Instead of using physical louvres that create Moiré patterns when their periodic structure interferes with pixel structures, the invention uses liquid crystal molecules whose orientation can be controlled by applied voltage. This substitution eliminates the periodic mechanical structure that causes Moiré artefacts while achieving the same privacy function through optical anisotropy control.
3Object-affected harmful factors
If removable louver films are added for privacy mode, then privacy function is provided, but reliable attachment and consistent activation cannot be ensured
Solution Approach 1:
The system incorporates automatic detection of ambient light conditions and automatically activates privacy mode when appropriate conditions are detected. The control system monitors environmental factors and user behavior patterns, then autonomously switches the liquid crystal layer to privacy mode without requiring manual user intervention. This self-service approach ensures consistent activation of privacy function based on actual usage contexts.
Solution Approach 2:
The invention implements feedback mechanisms where sensors detect ambient light levels, viewing conditions, and potentially user presence or device usage patterns. Based on this feedback information, the control system automatically adjusts the liquid crystal layer state to provide privacy when needed. This closed-loop control ensures that privacy mode is activated reliably and consistently based on actual environmental and usage conditions rather than relying on manual user action.
4Ease of operation
If user-dependent control is used for privacy mode activation, then user autonomy is maintained, but privacy mode is not reliably activated
Solution Approach 1:
The system incorporates automatic detection of ambient light conditions and automatically activates privacy mode when appropriate conditions are detected. The control system monitors environmental factors and user behavior patterns, then autonomously switches the liquid crystal layer to privacy mode without requiring manual user intervention. This self-service approach ensures consistent activation of privacy function based on actual usage contexts.
Solution Approach 2:
The invention implements feedback mechanisms where sensors detect ambient light levels, viewing conditions, and potentially user presence or device usage patterns. Based on this feedback information, the control system automatically adjusts the liquid crystal layer state to provide privacy when needed. This closed-loop control ensures that privacy mode is activated reliably and consistently based on actual environmental and usage conditions rather than relying on manual user action.
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
The system provides consistent privacy control, maintaining high image visibility for intended users while ensuring off-axis viewers cannot perceive the image, adaptable to varying ambient conditions and user preferences.
Implementation Method 1
a switchable liquid crystal retarder arranged between the output polariser and the additional polariser
Implementation Method 2
an output polariser arranged on the output side of the spatial light modulator; an additional polariser arranged on the output side of the output polariser
Implementation Method 3
Display backlights in general employ waveguides and edge emitting sources
Implementation Method 4
counter-propagating light may be extracted by reflection off tilted facets
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A control system for a switchable privacy display apparatus comprises an ambient light sensor and a display luminance controller arranged to control the luminance of the display in response to measured illuminance. High image visibility is provided for public mode operation while in privacy mode visual security level above a perceived privacy threshold may be obtained by means of control of image luminance, in response to the output of the ambient light sensor.