Single-Layer Light Guide Element for Wide Viewing Angle AR Displays
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Solution Overview
Problem
Current augmented reality (AR) and mixed reality (MR) headsets are heavy due to the need for high-resolution and wide viewing angle displays, leading to discomfort and limited user applications, while lightweight glasses-type displays have restricted functionality.
Innovation Solution
A light guide element with a single-layer substrate and a diffraction layer that includes a first diffraction grating for in-coupling and a second diffraction grating for out-coupling, allowing for a wide viewing angle and low weight, enabling a compact and lightweight display apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a heavy member is used for displaying ARMR images with high resolution and wide viewing angle, then the display quality is improved, but the weight of the headset increases and wearing comfort deteriorates
Solution Approach 1:
The patent combines multiple optical functions (diffraction grating, waveguide, and exit pupil expansion) into a single integrated light guide plate. This merging of functions eliminates the need for separate heavy optical components while maintaining ARMR display quality, directly resolving the contradiction between display performance and headset weight
Solution Approach 2:
The patent uses optical glass with specifically controlled refractive index (1.91 ≤ nd ≤ 2.05) to achieve the desired optical performance with a lighter weight material. By optimizing the refractive index parameter, the light guide plate can maintain high resolution and wide viewing angle while reducing weight compared to conventional optical materials
2Weight of moving object
If a single-layer light guide substrate is used, then the weight and complexity are reduced, but achieving wide viewing angle and high in-coupling efficiency becomes more difficult
Solution Approach 1:
The patent applies different diffraction grating structures at different locations on the single-layer light guide substrate. The input coupling grating is positioned at specific regions to capture light from the projector, while the exit pupil expansion grating is positioned at other regions to expand the viewing angle. This local differentiation of optical functions enables a single-layer structure to achieve wide viewing angle and high efficiency
Solution Approach 2:
The patent uses diffraction gratings to manipulate light in angular space, transforming the light propagation from a single direction to multiple directions. The exit pupil expansion grating specifically diffracts light to create an expanded exit pupil in the angular dimension, enabling wide viewing angle from a single-layer structure without adding physical layers
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 a lightweight and wide viewing angle display apparatus, expanding application fields and user ranges by optimizing the field of view for RGB wavelengths, enhancing visibility and reducing weight compared to conventional multi-layered optical elements.
Implementation Method 1
a first diffraction grating configured to in-couple light into the light guide substrate, the light being incident on the light guide substrate
Implementation Method 2
totally internally reflected light having propagated in the light guide substrate
Implementation Method 3
a second diffraction grating configured to outcouple totally internally reflected light having propagated in the light guide substrate out of the light guide substrate
Data Source
AI summary
A light guide element includes a light guide substrate that is a single-layer light guide substrate; and a diffraction layer formed on the light guide substrate. The diffraction layer includes a first diffraction grating configured to in-couple light into the light guide substrate; and a second diffraction grating configured to outcouple totally internally reflected light having propagated in the light guide substrate out of the light guide substrate. The first diffraction grating in-couples the incident light in a range of 60 degrees or more including a direction normal to substrate, for at least one of first wavelength of 450 nm±20 nm, second wavelength of 530 nm±20 nm, and third wavelength of 630 nm±20 nm. The second diffraction grating outcouples the totally internally reflected light in a range of 60 degrees or more including the direction normal to substrate, for at least one of the first, second, and third wavelengths.