Dual Waveguide Optical Device for Expanding Field of View
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Solution Overview
Problem
Current optical waveguides for AR/VR glasses have limited field of view, restricting the immersive experience due to the angular bandwidth of materials used, which is typically around 28.96° for single mode systems and 60° for dual mode systems, falling short of the human field of view effective for stereopsis at 114°.
Innovation Solution
The implementation of higher order diffraction modes and over-wavelength gratings in a double waveguide system, where each waveguide uses diffraction gratings configured for specific angular ranges, allowing for the coupling and replication of light across a wider angular span, effectively doubling the field of view to 137.7° by utilizing second-order diffraction and larger grating pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single mode diffraction is used in optical waveguide, then the device complexity is reduced, but the field of view is limited to 28.96°
Solution Approach 1:
The patent divides the field of view into multiple angular ranges, with each range handled by a dedicated waveguide layer. The first waveguide layer handles a first angular range using first diffraction modes, while the second waveguide layer handles a second angular range using second diffraction modes. This segmentation allows each layer to be optimized for its specific angular range, achieving a combined field of view that exceeds 114° without requiring any single layer to handle the entire range, thus maintaining manageable device complexity while dramatically expanding overall field of view.
Solution Approach 2:
The patent transitions from a single-plane diffraction approach to a multi-layer stacked architecture. By adding the vertical dimension with multiple waveguide layers, each layer can independently process different angular ranges. The first waveguide layer and second waveguide layer are stacked perpendicular to each other, with each layer's diffraction grating optimized for specific incident angle ranges. This dimensional transition enables the system to achieve ultra-wide field of view by combining the angular coverage of multiple layers.
2Adaptability or versatility
If dual mode diffraction is used in optical waveguide, then the field of view is extended to 60°, but the device complexity increases
Solution Approach 1:
Instead of using complex dual mode diffraction within a single layer, the patent segments the field of view handling across two separate waveguide layers. Each layer uses simpler single-mode diffraction optimized for its specific angular range. The first waveguide layer handles angles from -57° to +57°, while the second waveguide layer handles angles from -67° to +67°. This segmentation achieves the 60°+ field of view with reduced complexity compared to dual mode approaches.
Solution Approach 2:
The patent resolves the complexity issue by moving from horizontal complexity (dual modes in one layer) to vertical complexity (single mode in multiple layers). The stacked waveguide layer configuration allows each layer to use simpler diffraction gratings while the overall system achieves extended field of view through the combination of layers.
3Ease of manufacture
If larger grating pitches are used, then the fabrication complexity is reduced, but the diffraction angle range changes
Solution Approach 1:
The patent applies local quality by assigning different grating pitch values to different waveguide layers based on their specific angular range requirements. The first waveguide layer uses a first grating pitch optimized for its angular range, while the second waveguide layer uses a second grating pitch optimized for its angular range. This allows each layer to use larger, easier-to-fabricate gratings while maintaining the appropriate angular coverage for that layer, and the combination achieves the overall ultra-wide field of view.
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 significantly enhances the field of view to 137.7°, surpassing the human field of view effective for stereopsis, while simplifying fabrication by using larger grating pitches and reducing the complexity of nano-imprinting, thus providing a more immersive experience in AR/VR applications.
Implementation Method 1
an optical device, comprising: a first waveguide layer having a first diffraction grating configured to diffract an incident light into a first angular range and couple the diffracted light into the waveguide; a second waveguide layer having a second diffraction grating configured to diffract the incident light into a second angular range and couple the diffracted light into the waveguide
Implementation Method 2
light propagates into the optical waveguide by TIR (for Total Internal Reflection) only over a limited range of internal angles
Data Source
Figure 1A
Figure 1B~1C
Figure 1D~1E
AI summary
An example optical device includes a first waveguide (WG1) having a first diffractive in-coupler and a second waveguide (WG2) having a second diffractive in-coupler. The first diffractive in-coupler is configured to couple into the first waveguide (WG1) a first angular range ([-ThetaC WG1, -ThetaG WG1]) and a non-overlapping second angular range ([ThetaG WG1, ThetaC WG1]) of incident light. At least a portion of the incident light that is not coupled into the first waveguide (WG1) is transmitted to the second diffractive in-coupler. The second diffractive in-coupler is configured to couple a third angular range ([-ThetaG WG1- ThetaC WG1]) of the incident light, where the third angular range includes angles between the first angular range and the second angular range. Embodiments of the optical device may include an image generator for use in a display device.