Cropped Collector Mirror for Compact AR/VR Headsets
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Solution Overview
Problem
Existing augmented reality (AR) and virtual reality (VR) head-mounted displays (HMDs) with reflective optical elements face a challenge in achieving a reduced form factor while maintaining superior optical characteristics and image quality, as larger reflective collector elements detract from immersion due to their noticeable presence on the user's face.
Innovation Solution
The design incorporates a cropped reflective collector element that intentionally discards peripheral light, matching the etendue at the primary collecting mirror with that at the eyebox, thereby reducing the form factor without sacrificing image clarity and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If reflective collector elements are used to maintain superior optical characteristics, then image quality and brightness are improved, but the form factor increases and immersion is reduced
Solution Approach 1:
The patent extracts only the necessary central portion of the light source that contributes to the useful field of view, discarding the peripheral portions that would require larger collector elements. This is achieved by cropping the light source to match the etendue requirements, thereby reducing the collector element size while maintaining image brightness for the intended viewing area.
Solution Approach 2:
The patent changes the etendue parameter of the optical system by cropping the light source to match the eyebox etendue. This parameter change allows the reflective collector elements to be smaller while still delivering sufficient light to the user's eye, resolving the contradiction between brightness and form factor.
2Manufacturing precision
If reflective collector elements are used to maintain superior optical characteristics, then image clarity is improved, but the device size increases and ergonomics worsen
Solution Approach 1:
The patent extracts only the essential light rays that contribute to the desired field of view and image clarity, removing the peripheral light that would necessitate larger optical elements. This extraction allows for smaller, more ergonomic device dimensions while preserving the superior image clarity provided by reflective optics.
3Illumination intensity
If all light from the source is collected to maximize brightness, then illumination intensity is improved, but the collector element size increases
Solution Approach 1:
The patent changes the etendue parameter by cropping the light source to match the eyebox requirements. This parameter change enables the collector element to be smaller while still providing sufficient brightness for the intended field of view, as the cropped source already limits the light angles to those needed for the user's eye position.
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
This approach results in a miniaturized HMD with reflective elements that maintains superior optical properties and image quality, providing a more ergonomic and immersive experience by minimizing the physical presence of the device on the user.
Implementation Method 1
a cropped reflective collector element that intentionally discards peripheral light, matching the etendue at the primary collecting mirror with that at the eyebox
Data Source
AI summary
A device in which one or more reflective collector elements receive image data from one or more light-emitting visual sources to be transmitted to an eyebox, which together form elements of a head mounted display (“HMD”) useful for augmented reality (“AR”) or virtual reality (“VR”) applications, and where the one or more reflective collector elements are cropped to receive a portion of the image data from the one or more light-emitting visual sources, such that the etendue product at the one or more reflective collector elements is about the same as the etendue product within the eyebox.