Mixed Reality Display Waveguide Exit Pupil Expansion
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Solution Overview
Problem
Existing mixed reality near-eye displays face challenges in extending images to be clearly viewed from different directions due to the limited size of the near-eye display, which restricts the exit pupil expansion.
Innovation Solution
A mixed reality display device comprising a waveguide element, an image display device, an imaging lens, diffractive optical elements, and volume holographic optical elements, which work together to guide and expand the light field image, allowing for improved viewing angles and reduced vergence-accommodation conflict.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a near-eye display is used in mixed reality, then display convenience is improved, but the image incident area is limited which restricts exit pupil expansion
Solution Approach 1:
The patent employs a waveguide element that extends the image in the vertical dimension (from the small incident area on the display to a large exit area on the other side of the waveguide). The light field image is coupled into the waveguide through a first diffractive optical element, propagates through the waveguide, and is then coupled out through a second diffractive optical element, effectively expanding the image area from a small incident footprint to a large exit pupil area suitable for comfortable viewing.
Solution Approach 2:
The waveguide element acts as an intermediary between the small image incident area and the large image exit area. It receives the light field image from the near-eye display, guides it through its structure, and outputs an expanded version that can be viewed from different directions, thus resolving the area limitation while maintaining display convenience.
2Area of stationary object
If the image incident area is limited by the near-eye display size, then device compactness is improved, but the image exit area cannot be sufficiently expanded for multi-directional viewing
Solution Approach 1:
The waveguide element serves multiple functions: it acts as a light guide, an image expander, and a viewing angle controller. By integrating these functions into a single component, the patent avoids the need for separate optical elements for each function, thereby managing device complexity while achieving sufficient image exit area expansion for multi-directional viewing.
Solution Approach 2:
The optical system is segmented into distinct functional modules: the near-eye display generates the light field image, the first diffractive optical element couples it into the waveguide, the waveguide propagates and expands it, and the second diffractive optical element couples it out. This segmentation allows each component to be optimized independently while working together to achieve the overall goal of expanding the image exit area.
3Adaptability or versatility
If multiple optical elements are added to expand the image, then viewing angle is improved, but device complexity increases
Solution Approach 1:
The patent combines the waveguide element with diffractive optical elements at its input and output interfaces. The first diffractive optical element is integrated at the image incident side to couple light into the waveguide, while the second is integrated at the image exit side to couple light out. This merging of functions into integrated components achieves multi-directional viewing capability while managing the number of discrete optical elements.
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 enables clear viewing of 3D images from various angles, enhances the viewing experience by reducing dizziness caused by vergence-accommodation conflict, and improves image quality through effective exit pupil expansion.
Implementation Method 1
The imaging lens is located between the waveguide element and the image display device, and is configured to image the light field image at infinity, that is, transfer each signal pixel in the image display device into a plane wave at a corresponding angle
Implementation Method 2
The first diffractive optical element is located on a second side of the waveguide element opposite to the first side, and is configured to guide the light field image into the waveguide element
Implementation Method 3
The first volume holographic optical element is located on the second side of the waveguide element, and is configured to guide the light field image, wherein the first volume holographic optical element and the second volume holographic optical element have an angular selectivity, configured to extract a specific viewing angle
Data Source
AI summary
A mixed reality display device includes a waveguide element, an image display device, an imaging lens, a first diffractive optical element, a first volume holographic optical element, a second volume holographic optical element and a second diffractive optical element. The image display device is configured to emit a light field image. The imaging lens is configured to image an image at infinity. The first diffractive optical element is configured to guide the image into the waveguide element. The first volume holographic optical element and the second volume holographic optical element have an angle selectivity, configured to extract a specific field of view. The second volume holographic optical element has a lens array function to form a light field image source. The second diffractive optical element has a lens array function to transfer the light field image source into a three-dimensional image.