Directional Backlight Friction Gradient for Waveguide Protection
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Solution Overview
Problem
Existing directional displays face challenges with high losses and Moiré artefacts due to micro-louvre optical films, which require high inventory and cost, and are prone to damage from compressive forces, leading to image artefacts and reduced lifetime.
Innovation Solution
A directional backlight with a stack of components including a directional waveguide and optical components, where the coefficient of friction at the waveguide interfaces is greater than at outer interfaces, reducing damage and scatter, and allowing for switchable operation between wide angle and directional modes with reduced stray light.
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 patent removes the micro-louvre optical film from the system entirely, replacing it with a directional waveguide that achieves privacy functionality without the harmful losses and artefacts caused by micro-louvre structures
Solution Approach 2:
The patent uses imaging directional waveguides that create virtual images of light sources in specific viewing windows, copying the light source appearance for authorized viewers while preventing off-axis viewing, thereby achieving privacy without micro-louvre films
2Reliability
If waveguide interfaces have high friction to prevent damage, then component translation is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies different surface treatments to different locations: the waveguide interfaces receive high-friction treatment while outer interfaces maintain low friction, optimizing each location for its specific function without requiring complex overall structure
Solution Approach 2:
The patent modifies the coefficient of friction parameter at specific interfaces through surface treatments, changing the physical property to achieve desired mechanical behavior without altering the fundamental structure
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 enhances the durability and optical quality of directional displays by minimizing damage and artefacts, increasing the lifetime of the backlight, and reducing costs while providing efficient switchable privacy and autostereoscopic 3D capabilities.
Implementation Method 1
opposed first and second guide surfaces extending across the stack from the input end for guiding light input at the input end along the waveguide, the waveguide being arranged to deflect input light guided through the waveguide to exit through the first guide surface
Implementation Method 2
the coefficient of friction at the waveguide interfaces is greater than the coefficient of friction at at least one outer interface on each side of the waveguide in the stack
Data Source
AI summary
A backlight includes a directional waveguide and a light source array, for providing large area directed illumination from localized light sources. Interfaces are provided between the directional waveguide and optical components adjacent the directional waveguide such that the coefficient of friction at the waveguide interfaces is greater than the coefficient of friction at least one outer interface on each side of the waveguide in the stack. Damage from compressive forces on the optical stack may be reduced, achieving improved optical performance and lifetime. Privacy display, low stray light display and autostereoscopic display may be provided with high uniformity, long lifetime and reduced cost mechanical components.