Volume Holographic Waveguide for Wide-Field See-Through Displays
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Solution Overview
Problem
Existing VR and AR technologies suffer from inadequate field of view, with VR devices offering large views but no real-world visibility and AR devices providing smaller views with real-world integration.
Innovation Solution
An optical waveguide structure incorporating a volume holographic element and a liquid crystal element on opposite surfaces of an optical waveguide body, which modulates light to enhance the field of view beyond 80° while allowing real-world visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If VR devices use display screens to achieve large field of view, then field of view is improved, but real-world visibility is lost
Solution Approach 1:
The optical waveguide is divided into multiple functional zones: a first diffraction zone for coupling light into the waveguide, a second diffraction zone for coupling light out, and total internal reflection zones for guiding light. This segmentation allows different portions of the waveguide to perform different functions, enabling both large field of view and real-world visibility simultaneously.
Solution Approach 2:
Different regions of the optical waveguide have different optical properties. The first and second diffraction zones have specific diffraction grating structures for light coupling, while the total internal reflection zones have high refractive index for light guiding. This local differentiation of optical properties enables the waveguide to achieve both virtual image display and real-world visibility.
2Object-affected harmful factors
If AR devices use display screens to enable real-world visibility, then real-world visibility is improved, but field of view is reduced
Solution Approach 1:
The patent uses volume holographic elements that operate in three-dimensional space within the waveguide. By utilizing the vertical dimension (depth) of the waveguide structure, the system can achieve large field of view without increasing the lateral dimensions, thus maintaining real-world visibility while expanding the virtual image field of view to over 80 degrees.
Solution Approach 2:
The optical waveguide combines multiple materials with different optical properties: high refractive index materials for total internal reflection zones, diffraction grating materials for coupling zones, and volume holographic materials for selective light modulation. This composite structure enables simultaneous achievement of real-world visibility and large field of view.
3Area of moving object
If volume holographic element and liquid crystal element are added to optical waveguide, then field of view is improved, but device complexity increases
Solution Approach 1:
The volume holographic element and liquid crystal element are integrated into a single optical module that is coupled to the optical waveguide. This merging of components reduces the overall system complexity compared to having separate elements, while still achieving the dual functionality of polarization control and light coupling for large field of view.
Solution Approach 2:
The optical module containing both volume holographic and liquid crystal elements serves multiple functions: it controls polarization states, couples light into and out of the waveguide, and enables large field of view display. This multi-functionality reduces the need for additional separate components, thereby managing device complexity.
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 structure achieves a large field of view exceeding 80° and integrates real-world visibility, enhancing user experience by combining virtual and augmented reality imaging.
Implementation Method 1
the liquid crystal element is configured for selectively diffracting and transmitting light
Implementation Method 2
the volume holographic element is configured for rotating a polarization direction of the first circularly polarized light to form a second circularly polarized light
Implementation Method 3
the optical waveguide body includes a first surface and a second surface which are provided oppositely to each other
Data Source
AI summary
The present disclosure provides an optical waveguide structure and a head mounted display. The optical waveguide structure includes an optical waveguide body, a volume holographic element, and a liquid crystal element; the volume holographic element is provided on a first surface, and the liquid crystal element is provided on a second surface; the liquid crystal element is configured for selectively diffracting and transmitting light, the light includes a first circularly polarized light with a first polarization state which is diffracted towards the volume holographic element, the volume holographic element is configured for rotating a polarization direction of the first circularly polarized light to form a second circularly polarized light with a second polarization state which is then diffracted towards the liquid crystal element, and the second circularly polarized light is transmitted and then coupled out of the optical waveguide body.