Head-worn Display Holographic Optical Element for Expanded Eyebox
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Solution Overview
Problem
Current head-worn displays (HWDs) face challenges in expanding the eyebox while maintaining a compact and aesthetically pleasing form factor, as conventional methods for increasing the field of view often result in bulky optics and trade-offs in weight and optical bulk.
Innovation Solution
A method and apparatus using a scanning projection system with a small etendue source, such as a laser or LED, and a volume holographic optical element (HOE) as a transflector to create multiple small exit pupils that can be strategically placed for an enlarged effective eyebox, allowing ambient light to pass through while redirecting scanned light to the eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional methods are used to expand the field of view in head-worn displays, then the field of view increases, but the optical system becomes bulky and heavier
Solution Approach 1:
The patent divides the single exit pupil into multiple exit pupils (first exit pupil and second exit pupil) that are spatially separated. This segmentation allows the optical system to cover a larger effective eyebox area without requiring each individual pupil to be large, thereby avoiding the need for bulky optics while still achieving an expanded field of view.
Solution Approach 2:
The patent transitions from a single-point exit pupil to a distributed array of multiple exit pupils in different spatial locations. This dimensional change from one location to multiple locations allows the system to expand the effective viewing area without increasing the size of individual optical components.
2Adaptability or versatility
If the exit pupil is expanded to increase the eyebox, then the eyebox tolerance improves, but the optical system becomes more bulky
Solution Approach 1:
The patent segments the exit pupil into multiple distinct exit pupils located at different positions. This segmentation provides adaptability by allowing the eye to accommodate from multiple discrete locations, effectively increasing eyebox tolerance without requiring each individual exit pupil to be enlarged, thus avoiding increased optical bulk.
3Volume of stationary object
If a single exit pupil is used, then the optical system is compact, but the eyebox is limited and restricts field of view
Solution Approach 1:
The patent divides the single exit pupil into multiple exit pupils (first exit pupil and second exit pupil) that are spatially separated. This segmentation increases the effective eyebox area by providing multiple viewing locations without requiring each individual pupil to be large, thereby maintaining compact optics while expanding the usable eyebox area.
Solution Approach 2:
The patent combines multiple exit pupils into a unified optical system that works together to provide an expanded effective eyebox. By merging the functionality of multiple pupils into a single integrated system, the patent achieves a larger eyebox area while keeping the overall optical bulk compact.
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 enables an expanded eyebox with reduced optical bulk, allowing for a larger field of view while maintaining a lightweight and socially acceptable form factor, and can be used for both monocular and binocular implementations.
Implementation Method 1
a volume holographic optical element (HOE) as a transflector to create multiple small exit pupils
Implementation Method 2
redirecting scanned light to the eye
Data Source
Figure 0.1
Figure 1A~1B
Figure 2A~2B
AI summary
Head-worn display comprising a light source emitting a plurality of light beams, two of which having different wavelengths, a scanning mirror (212) to scan the plurality of light beams in two distinct axes to form an image, a holographic optical element (201) to receive the plurality of scanned light beams from the scanning mirror (212) and to redirect them to a plurality of spatially-separated exit pupils (212, 304) to project the image at the plurality of exit pupils, and a frame (1001) to hold the light source, the scanning mirror (212), and the holographic optical element (201) in fixed relation to one another, said frame (1001) being adapted to be worn on a user's head.