Optical Waveguide With Symmetrical Grating for Compact HUD Pupil Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing waveguide designs for head-up displays (HUDs) face challenges in expanding the exit pupil in two dimensions without increasing size or reducing luminance, leading to non-uniform brightness and asymmetric views, particularly in applications where space is limited.
Innovation Solution
A symmetrical diffraction grating waveguide design with a single or dual input region that expands the pupil while maintaining luminance and reducing complexity, using fewer diffraction gratings and simplified fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional waveguide designs are used to expand the exit pupil in two dimensions, then the pupil expansion is achieved, but the waveguide size increases and luminance decreases
Solution Approach 1:
The patent transitions from two-dimensional pupil expansion to three-dimensional pupil expansion by introducing a focal volume within the waveguide. This focal volume acts as an intermediate stage that enables compact two-dimensional exit pupil expansion while maintaining a small waveguide footprint, effectively using the third dimension (depth within the waveguide) to achieve the expansion goal.
2Area of moving object
If conventional waveguide designs are used to expand the exit pupil, then the pupil expansion is achieved, but luminance decreases and non-uniformities appear
Solution Approach 1:
The patent introduces a focal volume with specific local optical properties within the waveguide that concentrates and redistributes light uniformly. This localized focal region ensures uniform luminance across the expanded exit pupil by controlling the light distribution at that specific location, preventing non-uniformities while maintaining high luminance.
3Adaptability or versatility
If asymmetrical waveguide designs are used, then the field of view is expanded, but different designs are required for left and right seat installations
Solution Approach 1:
The patent employs asymmetrical diffraction gratings with different periods in the x and y directions to create a symmetrical focal volume. This approach allows the waveguide to provide a symmetrical field of view and uniform pupil expansion in both left and right seat installations, eliminating the need for different designs while maintaining expanded 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
The design achieves symmetrical pupil expansion with reduced complexity and cost, minimizing pupil banding and maintaining consistent brightness across the field of view, suitable for compact HUD systems.
Implementation Method 1
The waveguide comprises a diffraction grating. The diffraction grating may be configured to receive light from the input region and diffract the light towards an output region of the waveguide
Implementation Method 2
The waveguide may be configured to receive and couple light through a single input region into the waveguide
Data Source
AI summary
An optical waveguide for a head up display is disclosed. The optical waveguide is configured to provide pupil expansion in two dimensions and having an input end and an output end and a first axis substantially parallel to the direction of propagation of light in the waveguide and substantially parallel with a direction from the input end to the output end. The optical waveguide comprising: an input region at the input end; a beam splitter configured to expand light received from the input region; a symmetrical diffraction grating comprising complementary first and second grating portions, wherein the second grating portion is substantially symmetrical to the first grating portion along a line of symmetry that is substantially parallel to the first axis. Light received at the symmetrical diffraction grating from the beam splitter is configured to be diffracted by the symmetrical diffraction grating towards the line of symmetry by the first grating portion or the second grating portion. Light received at the first grating portion from the second waveguide portion is configured to be diffracted out of the waveguide at the output end. Light received at the second grating portion from the first grating portion is configured to be diffracted out of the waveguide at the output end.