Observer-Tracked Privacy Display for Off-Axis Luminance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing display devices suffer from non-uniform luminance across the display area, particularly in off-axis viewing conditions, which affects privacy and visibility, and existing switchable privacy displays do not adequately address this issue.
Innovation Solution
A display apparatus comprising a spatial light modulator, a display polariser, an additional polariser, and at least one polar control retarder with a switchable liquid crystal retarder and electrode arrangements to control the electric field perpendicular to the liquid crystal material, allowing for adjustable luminance control based on viewer location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switchable liquid crystal retarders and compensation retarders are used to control off-axis luminance, then privacy control capability is improved, but luminance uniformity across the display area deteriorates
Solution Approach 1:
The patent applies local quality by varying the tilt angle of liquid crystal molecules across different regions of the display. Specifically, the tilt angle is adjusted locally in off-axis regions to reduce luminance for snoopers while maintaining uniform luminance in the on-axis viewing region. This spatial variation in molecular orientation allows differential privacy control without compromising overall luminance uniformity.
Solution Approach 2:
The patent changes physical parameters of the liquid crystal layer, specifically the tilt angle distribution across the display area. By controlling the tilt angle parameter to be position-dependent (with maximum tilt in off-axis regions and minimal tilt in on-axis regions), the system achieves both privacy control and luminance uniformity simultaneously.
2Illumination intensity
If micro-louvre optical films are used to provide privacy function, then off-axis luminance reduction is improved, but switchability is lost
Solution Approach 1:
The patent replaces static micro-louvre films with dynamic liquid crystal structures that can change their optical properties on demand. The liquid crystal molecules can be electrically controlled to adopt different orientations, enabling the display to switch between privacy mode (with off-axis luminance reduction) and share mode (without reduction), thus providing both effective privacy control and switchability.
Solution Approach 2:
The patent substitutes the mechanical micro-louvre film structure with an electrically controlled liquid crystal system. Instead of relying on fixed physical structures to control light direction, the system uses electric fields to control liquid crystal molecular orientation, enabling dynamic and reversible privacy control.
3Object-generated harmful factors
If off-axis luminance reduction is applied to reduce stray light, then reflection reduction is improved, but luminance non-uniformity increases
Solution Approach 1:
The patent applies local quality by selectively reducing luminance only in off-axis regions where stray light and reflections occur. The liquid crystal tilt angle is maximized in these peripheral regions to redirect off-axis light, while the central on-axis region maintains uniform luminance for the primary viewer. This localized approach reduces reflections without creating noticeable luminance non-uniformity.
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 apparatus provides controllable luminance for desirable observer locations, increasing the size of the polar region for high image security and visibility, reducing luminance non-uniformity, and minimizing distractions for off-axis viewers.
Implementation Method 1
a switchable liquid crystal retarder comprising a layer of liquid crystal material
Implementation Method 2
first and second electrode arrangements disposed on opposite sides of the layer of liquid crystal material and arranged to provide an electric field perpendicular to the layer of liquid crystal material
Implementation Method 3
the surface alignment layers each being arranged to provide homogenous alignment in the adjacent liquid crystal material, the liquid crystal material being provided with a twist
Implementation Method 4
a display polariser arranged on a side of the spatial light modulator, the display polariser being a linear polariser; and an additional polariser arranged on the same side of the spatial light modulator as the display polariser, the additional polariser being a linear polariser
Data Source
AI summary
A display device comprising a spatial light modulator having a display polariser arranged on one side is provided with an additional polariser arranged on the same side as the display polariser and a polar control retarder between the additional polariser and the display polariser. The polar control retarder includes a liquid crystal retarder having two surface alignment layers disposed adjacent to a layer of liquid crystal material on opposite sides. The surface alignment layers provide alignment in the adjacent liquid crystal material with a twist. The out-of-plane orientation of the twisted layer of liquid crystal material is modified across at least one region of the display device to provide a transmission function in response to the measured location of an off-axis snooper, achieving increased size of polar region for which desired uniformity of security factor, or reduced distraction across the display to the driver in an automotive application is achieved.