Pupillated Backlight with Prismatic Turning Film for Privacy Displays
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Solution Overview
Problem
Existing privacy displays face challenges in providing effective control over image visibility, with micro-louvre optical films causing high losses and Moiré artefacts, and existing solutions require user intervention or have unreliable attachment mechanisms.
Innovation Solution
An illumination apparatus featuring a waveguide arrangement and an optical turning film component with prismatic elements that deflect light uniformly across a plane, allowing for controlled light distribution and increased uniformity, and a control system to independently manage light sources for enhanced privacy and public modes.
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 illumination losses increase and Moiré artefacts occur
Solution Approach 1:
The optical film is segmented into multiple discrete microlouvre elements arranged in an array, where each element independently controls light transmission at different angles. This segmentation allows precise angular selectivity to reduce off-axis visibility while maintaining head-on illumination efficiency.
Solution Approach 2:
The microlouvre elements have locally optimized geometries with varying pitch, width, and orientation angles tailored to specific regions of the display. This local quality optimization ensures that each region provides appropriate privacy protection while minimizing illumination losses for its specific viewing direction.
2Manufacturing precision
If micro-louvre pitch is selected for panel resolution, then image quality is maintained, but inventory and cost increase
Solution Approach 1:
A single microlouvre optical film design with optimized pitch and geometry serves multiple functions: it provides privacy protection, maintains image quality across different panel resolutions, and reduces the need for multiple specialized films. This universal design approach decreases inventory requirements and manufacturing costs.
Solution Approach 2:
The microlouvre pitch and geometric parameters are optimized to a standard value that provides acceptable performance across a range of panel resolutions. This parameter standardization allows the same optical film to be used with different display panels, reducing inventory complexity and manufacturing costs.
3Object-affected harmful factors
If removable louver film is added for privacy mode, then privacy function is provided, but reliability of attachment decreases
Solution Approach 1:
The microlouvre optical film is permanently integrated into the display assembly during manufacturing, merging the privacy function with the display structure. This integration eliminates attachment and removal operations, ensuring reliable and consistent privacy protection without the risks of user handling errors or improper attachment.
Solution Approach 2:
The display assembly itself provides the privacy function through the integrated microlouvre film, eliminating the need for separate removable components that require user attachment. The privacy protection is self-contained within the display structure, ensuring reliable operation without user intervention.
4Ease of operation
If user intervention is required to activate privacy mode, then control is provided, but ease of operation decreases
Solution Approach 1:
The display assembly provides automatic privacy protection through its integrated microlouvre optical film, which inherently blocks off-axis viewing without requiring any user activation or intervention. The privacy function operates continuously as part of the display's basic operation, eliminating time loss and simplifying user interaction.
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 solution provides improved luminance uniformity and privacy control, reducing user intervention and attachment issues, while maintaining high efficiency and visibility for primary users while minimizing visibility for off-axis observers.
Implementation Method 1
first and second opposed light guiding surfaces arranged to guide light along the first waveguide, the second light guiding surface being arranged to guide light by total internal reflection
Implementation Method 2
an array of prismatic elements each comprising a pair of facets defining a ridge therebetween, wherein the prismatic elements are arranged to deflect the light exiting the first waveguide
Data Source
AI summary
A switchable backlight for a switchable privacy display apparatus comprises a collimated waveguide, first and second light sources and an optical turning film comprising elongate prismatic elements with facet orientations that pupillate the output of the waveguide in two orthogonal directions for each of first and second light sources. High luminance uniformity is achieved for a head-on user in privacy and public viewing modes and high uniformity of security factor is achieved for off-axis snoopers, with increased speed of privacy switch-on in privacy mode.