Mixed Reality Waveguide Exit Pupil Expansion Using Diffractive Lens Arrays
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Solution Overview
Problem
Existing mixed reality near-eye displays face challenges in extending the image exit pupil to allow clear viewing from different directions, due to the limited size of the near-eye display.
Innovation Solution
A mixed reality display device incorporating a waveguide element, an image light source, and two diffractive optical element lens arrays, where the first array converges light and the second array diverges or converges light, forming an afocal system to achieve exit pupil expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the near-eye display size is limited, then the device portability is improved, but the image exit pupil area is reduced
Solution Approach 1:
The patent uses a waveguide structure that extends the optical path in the z-dimension (depth), allowing the image to propagate through the waveguide thickness and emerge at multiple positions. This dimensional extension enables a larger effective exit pupil area without increasing the lateral footprint of the near-eye display, thus maintaining portability while expanding the viewing area.
Solution Approach 2:
The patent embeds multiple diffractive optical element lens arrays within the waveguide structure. These lens arrays are nested inside the waveguide thickness, with each array contributing to expanding the exit pupil in different directions. This nesting approach allows multiple optical functions to be packed into a compact form factor, achieving large exit pupil area without increasing device size.
2Adaptability or versatility
If the image exit area is extended for multi-directional viewing, then the viewing experience is improved, but the near-eye display size must increase
Solution Approach 1:
The waveguide structure utilizes the thickness dimension to enable multi-directional light extraction. By positioning diffractive optical element lens arrays at different depths within the waveguide, the system can direct light toward the eye from multiple angles and positions, achieving versatile multi-directional viewing without expanding the lateral display area.
Solution Approach 2:
The waveguide acts as an intermediary medium that receives the image from the near-eye display and redistributes it to multiple exit positions. The diffractive optical element lens arrays within the waveguide serve as intermediaries that manipulate light propagation directions, enabling multi-directional viewing capability while keeping the original display size compact.
3Area of stationary object
If diffractive optical element lens arrays are used to magnify field of view, then exit pupil expansion is achieved, but the device complexity increases
Solution Approach 1:
The patent combines multiple diffractive optical element lens arrays within a single waveguide structure, merging their functions to achieve cumulative exit pupil expansion. Rather than using separate optical systems for each expansion function, the arrays are integrated into one unified waveguide device, reducing overall system complexity while maintaining the benefits of multiple lens arrays.
Solution Approach 2:
The patent uses diffractive optical elements to replace traditional refractive or reflective optical systems. Diffractive elements can be fabricated directly into the waveguide using microfabrication techniques, eliminating the need for separate mechanical lens assemblies and reducing device complexity. The diffractive structures achieve the same optical functions with simpler integration.
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 effectively magnifies the field of view, achieving exit pupil dilation and enhancing the viewing experience in mixed reality displays by allowing the human eye to see the image from different angles.
Implementation Method 1
The image light source is located in the waveguide element, and is configured for total internal reflection to on an image to be transferred
Implementation Method 2
The first diffractive optical element lens array includes a plurality of diffractive optical element lenses. The diffractive optical element lenses are arranged in an array, and any of the diffractive optical element lenses is configured to converge a light. The second diffractive optical element lens array includes a plurality of diffractive optical element lenses. The diffractive optical element lenses are arranged in an array, and any of the diffractive optical element lenses is configured to diverge or converge a light.
Data Source
AI summary
A mixed reality display device includes a waveguide element, an image light source, a first diffractive optical element lens array and a second diffractive optical element lens array. The image light source is located in the waveguide element. The first diffractive optical element lens array is located on a first side of the waveguide element facing a human eye, the first diffractive optical element lens array includes a plurality of diffractive optical element lenses, and any of the diffractive optical element lenses is configured to converge a light. The second diffractive optical element lens array is located on a second side of the waveguide element opposite to the first side, the second diffractive optical element lens array includes a plurality of diffractive optical element lenses, and any of the diffractive optical element lenses is configured to diverge or converge a light.