Multi-pupil lightguide element for expanding AR display field of view
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Solution Overview
Problem
Existing diffractive display technologies for augmented reality near-to-eye displays (NEDs) or head-mounted displays (HMDs) face challenges in achieving a large field of view (FOV) while maintaining a small device size and ensuring full color reproduction.
Innovation Solution
The solution involves splitting the FOV of the total image into partial FOVs directed to a diffractive waveguide element through multiple pupils, using a multi-pupil lightguide element and projector. This design allows for the recombination of partial FOVs into a larger total image viewable by the user, using overlapping out-coupling gratings and spatially separated in-coupling gratings to prevent ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple lightguides with stacked in-coupling gratings are used to increase FOV, then the field of view expands, but the in-coupling process becomes difficult to control and ghost images occur
Solution Approach 1:
The invention divides the total FOV into multiple partial FOVs, with each lightguide responsible for a specific angular range. The in-coupling gratings are laterally displaced rather than stacked, creating spatial separation between different FOV segments. This segmentation approach allows independent optimization of each lightguide while avoiding the interference and ghost images that occur with stacked gratings.
2Adaptability or versatility
If conventional stacked in-coupling gratings are used, then multiple wavelength bands can be in-coupled, but the entire lightguide stack must be optimized as a whole which is cumbersome and time-consuming
Solution Approach 1:
By laterally displacing the in-coupling gratings in different lightguides, the invention enables independent optimization of each lightguide for its specific wavelength band and angular range. Each lightguide can be designed and optimized separately rather than requiring holistic optimization of the entire stack, significantly reducing design complexity and development time.
3Ease of manufacture
If three different light guides are used to obtain red, green and blue image channels, then color reproduction is achieved, but resolution and wavelength band are limited
Solution Approach 1:
Instead of using three separate light guides stacked vertically (z-dimension), the invention laterally displaces (x-dimension) the in-coupling gratings of multiple lightguides. This lateral arrangement allows multiple wavelength bands to be in-coupled simultaneously without the resolution and wavelength band limitations of vertical stacking, while maintaining color reproduction capability.
4Area of stationary object
If non-waveguide-based optical systems are used to achieve larger FOV, then field of view increases, but device size becomes too large for AR applications
Solution Approach 1:
The invention embeds multiple lightguides within a compact stacked arrangement, with each lightguide containing laterally displaced in-coupling gratings. This nested structure allows the system to achieve large FOV equivalent to non-waveguide systems while maintaining the compact form factor required for AR applications.
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 significantly increases the total FOV without splitting the wavelength band, allowing for a smaller projector size and easier lightguide optimization. It also enables full color reproduction and reduces the risk of ghost images, making the technology more efficient and effective.
Implementation Method 1
the in-coupling gratings of the lightguides are typically laterally coincident and stacked on top of each other
Implementation Method 2
lightguide element and projector therefor, and method for displaying image
Implementation Method 3
the diffractive out-coupling means of the multi-pupil lightguide element may comprise at least two out-coupling gratings laterally overlapping each other on the lightguide means
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
The invention concerns a multi-pupil lightguide element, a diffractive personal display, multi-pupil projector, a method for displaying an image and a use. The element comprises lightguide means (51, 55), diffractive in-coupling means (52, 56) for coupling an image directed to the in-coupling means (52, 56) into the lightguide means (51, 55), and diffractive out-coupling means (54, 58) for coupling said image out of the lightguide means (51, 55). According to the invention, the diffractive in-coupling means (52, 56) comprise at least two in-coupling gratings (52, 56) laterally displaced from each other on said lightguide means (51, 55) for receiving segments of said image, and the diffractive out-coupling means (54, 48) is optically associated with said at least two in-coupling gratings (52, 56) for reproducing said image from said image segments. The invention allowsfor expanding the field-of-view of near-to-eye displays, for example.