Waveguide Display Leakage Reduction via Volume Grating
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Solution Overview
Problem
Waveguide-type display apparatuses face the challenge of image leakage, where light diffracted to higher order terms by diffractive optical elements is output to the outside, potentially invading privacy and causing noise emission.
Innovation Solution
Incorporating an optical element with a volume grating and a deflection element, configured to deflect leakage light at an angle greater than its incident angle, and a light absorber with high absorbance, to reduce leakage light output and prevent external observation of images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a diffractive optical element is used to direct image information in a waveguide display, then the display can be realized in a small volume with thin components, but light diffracted to higher order terms leaks out through the waveguide surface causing noise and privacy invasion
Solution Approach 1:
The patent extracts and removes the harmful higher-order diffracted light from the system by introducing a dedicated optical element (light absorber or secondary diffractive element) that selectively targets and eliminates only the unwanted higher-order terms, while preserving the useful zero-order and first-order diffracted light for normal display operation
Solution Approach 2:
The patent applies local quality by making the waveguide structure non-uniform - specifically, by creating a gradient in the refractive index or by varying the thickness of the waveguide layer in specific regions. This local variation in optical properties allows selective control of light propagation, enabling higher-order diffracted light to be directed toward absorption regions while maintaining normal waveguide functionality in other areas
2Productivity
If the waveguide transmits all light propagating through it, then the display function is maintained, but leakage light exits the waveguide surface without total internal reflection, enabling external observation and privacy invasion
Solution Approach 1:
The patent applies preliminary action by pre-configuring the waveguide structure with specific optical properties (refractive index gradient, varying thickness) before light enters, and by pre-positioning light absorbers or secondary diffractive elements at strategic locations. This preliminary setup ensures that higher-order diffracted light is automatically redirected toward absorption or eliminated before it can leak out and invade privacy
Solution Approach 2:
The patent introduces an intermediary optical element (such as a light absorber material or a secondary diffractive optical element) that acts as a mediator between the propagating light and the waveguide boundary. This intermediary selectively interacts with higher-order diffracted light, absorbing it or redirecting it, while allowing the main display light to pass through unaffected, thus preventing privacy invasion without compromising display function
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
Effectively minimizes image leakage by redirecting and absorbing diffracted light, ensuring privacy and reducing noise emission while allowing transmission of light from the real environment.
Implementation Method 1
an optical element comprising a volume grating configured to reduce leakage light, among the light propagating through the first waveguide, which exits the first waveguide without total internal reflection
Implementation Method 2
The deflection element may be configured to deflect light at an deflection angle greater than an incident angle of the leakage light by at least a portion of the volume grating based on the leakage light being incident on the volume grating
Implementation Method 3
light deflected from the deflection element may be totally internally reflected and propagated in the second waveguide
Implementation Method 4
The optical element may further comprise a light absorber provided on the second waveguide
Data Source
AI summary
A waveguide type display apparatus is provided. This waveguide type display apparatus includes a waveguide through which an image proceeds and a leakage image reducer configured to reduce emission of a leakage image leaked from the waveguide without total internal reflection in the waveguide, from among images, to the outside by a volume grating.