Waveguide Reflector Surface for Compact Optical Function
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Solution Overview
Problem
Existing waveguide displays in personal display devices, such as HMDs and HUDs, face challenges in efficiently modifying the light field due to limited surface area, which restricts the performance of optical functions like exit pupil expansion and out-coupling.
Innovation Solution
The introduction of a curved reflector surface within the waveguide plane or perpendicular to it allows for the redirection of propagating rays without the need for extensive in-plane gratings, thereby optimizing space usage and enhancing optical functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If in-plane gratings are used to perform optical functions inside the waveguide, then optical functions such as exit pupil expansion and out-coupling can be achieved, but the surface area required on the waveguide becomes excessively large
Solution Approach 1:
The patent transitions from using grating structures that operate within the waveguide's main plane to a reflector surface that utilizes the third dimension (depth/thickness of the waveguide). By positioning the reflector at an angle within the waveguide's thickness, the solution moves the optical function from the two-dimensional surface to a three-dimensional configuration, thereby achieving optical functionality without consuming valuable in-plane surface area.
Solution Approach 2:
The reflector surface acts as an intermediary element that redirects light paths within the waveguide. Instead of using gratings that directly couple light in or out of the waveguide, the reflector serves as a mediating structure that redirects propagating rays to achieve optical functions like exit pupil expansion and out-coupling, thereby reducing the need for large grating surfaces.
2Area of stationary object
If the waveguide surface area is reduced to fit practical display devices, then the device becomes more compact and suitable for near-to-the-eye applications, but the optical functions become too limited
Solution Approach 1:
By utilizing the third dimension (waveguide thickness) for the reflector surface, the patent achieves optical functionality without requiring large in-plane surface area. This dimensional transition allows the waveguide to maintain a compact footprint while still providing sophisticated optical functions such as light field compression, decompression, and out-coupling.
Solution Approach 2:
The reflector surface is positioned at a specific location and orientation within the waveguide (at an angle to the waveguide plane), creating a localized optical function that does not require extensive surface coverage. This localized approach allows complex optical functions to be achieved in a compact space, improving the waveguide's adaptability without increasing its overall size.
3Adaptability or versatility
If additional optical components are integrated into the waveguide to enhance functionality, then the optical performance improves, but the surface area consumption increases
Solution Approach 1:
The patent merges the reflector surface with the waveguide structure itself, integrating the optical function directly into the waveguide's existing geometry rather than adding separate external components. This integration allows multiple optical functions (light field compression, decompression, out-coupling) to be achieved within the waveguide's inherent structure, avoiding additional surface area consumption.
Solution Approach 2:
By positioning the reflector in the third dimension (within the waveguide thickness) rather than on the surface, the patent enables integration of additional optical functionality without increasing the waveguide's in-plane footprint. This spatial arrangement allows multiple optical components to be integrated vertically rather than horizontally, preserving surface area for other functions.
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 solution enables the performance of complex optical functions like light field compression and decompression, exit pupil expansion, and integration of additional components within the waveguide, without consuming valuable surface area, thus improving the efficiency and field of view in virtual and augmented reality applications.
Implementation Method 1
the reflector surface is adapted to redirect light rays propagating within the waveguide between said main surfaces via total internal reflections
Implementation Method 2
a planar waveguide... adapted to redirect light rays propagating within the waveguide between said main surfaces via total internal reflections
Data Source
Figure 1A~1B
Figure 2~4
AI summary
The invention provides waveguide display element comprising a waveguide (10) comprising two opposing main surfaces, a first optical element arranged at a first location of the waveguide (10), a second optical element arranged at a second location of the waveguide (10), and at least one reflector surface (12A, 14A) extending between said main surfaces and adapted to reflect light rays propagating within the waveguide (10). The reflector surface (12A, 14A) is adapted to redirect light rays from the first optical element to the second optical element.