Composite Prism Light Guide with Polarization Separator for Dual Image HMDs
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) face challenges in providing both infinity-focused and near-field focused virtual images using bulky designs and complex timing schemes, making it difficult to implement in lightweight, wearable devices that also allow visibility of the real-world scene.
Innovation Solution
The use of two or more light guides and a beam separator with a composite prism and polarization beam splitter to form virtual images at infinity and near-field focus, allowing a single image source to project dual image content with different focal lengths, using beam expanders and reflective surfaces to direct polarized light for image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bulky designs with multiple image-forming components are used to provide both near-field and infinity-focused images, then dual image content can be displayed, but the device weight and complexity increase significantly
Solution Approach 1:
The patent combines multiple image-forming functions into a single light guide component. The light guide simultaneously forms both near-field and infinity-focused virtual images using a single optical element with multiple exit surfaces, eliminating the need for separate image-forming components for each focal distance.
Solution Approach 2:
The light guide is designed as a multi-functional component that can form virtual images at different focal distances (near-field and infinity) and provide real-world scene visibility through the same optical element. This universal component replaces what would traditionally require multiple specialized components.
2Adaptability or versatility
If multiple image-forming components are used to provide both near-field and infinity-focused images, then dual image content can be displayed, but the device complexity increases
Solution Approach 1:
The patent merges multiple image-forming functions into a single light guide component. The light guide simultaneously forms both near-field and infinity-focused virtual images using a single optical element with multiple exit surfaces, eliminating the need for separate image-forming components for each focal distance.
Solution Approach 2:
The light guide is designed as a multi-functional component that can form virtual images at different focal distances (near-field and infinity) and provide real-world scene visibility through the same optical element. This universal component replaces what would traditionally require multiple specialized components.
3Reliability
If conventional light guides are used, then infinity-focused virtual images can be displayed, but near-field focused images cannot be formed
Solution Approach 1:
The light guide is segmented into multiple functional regions with different exit surfaces. Each exit surface is configured to form virtual images at different focal distances - one surface for infinity-focused images and another for near-field focused images, allowing both functions to coexist in a single component.
Solution Approach 2:
The patent adds the dimension of multiple exit surfaces to the conventional light guide structure. By creating different exit surfaces at different locations or orientations on the light guide, it enables formation of virtual images at different focal distances without compromising the reliability of infinity-focused image display.
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
Enables the creation of a compact HMD that can display both infinity-focused and near-field focused virtual images, while maintaining visibility of the real-world scene, using a single image source and reducing the need for multiple components, thereby enhancing the usability of head-mounted optical imaging apparatus.
Implementation Method 1
A first polarization beam splitter surface encased within the composite prism redirects, along a direction substantially orthogonal to the input face, light of a first polarization that reflects from the polarization beam splitter
Implementation Method 2
A first reflective surface is disposed to redirect, along a direction orthogonal to the input face, light of a first polarization that reflects from the polarization beam splitter
Implementation Method 3
Such diffractive optics can be formed as diffraction gratings, holographic optical elements or in other known ways
Data Source
AI summary
A beam separator has a composite prism having an external input face and an external output face co-planar to the input face. At least one polarization beam splitter surface is encased within the composite prism and has an edge that defines a boundary between the external input face and the external output face. A first reflective surface is disposed to redirect, along a direction orthogonal to the input face, light of a first polarization that reflects from the at least one polarization beam splitter.