Symmetrical HUD Waveguide Layout for Uniform Exit Pupil
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Solution Overview
Problem
Existing waveguide designs for head-up displays (HUDs) face challenges in providing a large, uniform exit pupil while maintaining luminance and symmetry, often resulting in nonuniform brightness and asymmetric views, especially when eye movement occurs.
Innovation Solution
A symmetrical single-input and dual-input waveguide design with a beam-splitter and symmetrical diffraction grating that expands the pupil while minimizing diffraction gratings, reducing complexity and fabrication steps, and allowing for a more uniform exit pupil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If waveguide expansion is performed in two-dimensions, then the exit pupil becomes larger, but the luminance for each pupil decreases
Solution Approach 1:
The patent transitions from conventional two-dimensional pupil expansion to three-dimensional expansion by utilizing the waveguide thickness dimension. Multiple exit pupils are formed at different depths within the waveguide, allowing the system to achieve a larger effective exit pupil volume without diluting the luminance of individual pupils, as each pupil maintains its brightness while occupying a different spatial plane
2Adaptability or versatility
If asymmetric waveguide designs are used, then the field of view becomes asymmetric, but different designs are required for left and right seat installations
Solution Approach 1:
The patent employs asymmetric diffraction grating structures within a symmetrical waveguide geometry to generate asymmetric optical fields. By strategically positioning and configuring the diffraction gratings, the system can produce different field of view characteristics for left and right seats using a single universal waveguide design, eliminating the need for separate asymmetric waveguide designs for each installation position
3Weight of stationary object
If conventional optics are used, then mass and volume are reduced compared to lenses and prisms, but space-constrained environments still face accommodation challenges
Solution Approach 1:
The patent utilizes thin-film waveguide structures with integrated diffractive optical elements that can be fabricated as lightweight, planar components. These thin-film implementations provide the necessary optical functionality with minimal mass and volume, enabling installation in space-constrained environments where even conventional compact optics would be too large, while maintaining the weight advantages of waveguide-based systems
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 proposed waveguide design achieves a larger, uniformly bright exit pupil with reduced complexity and cost, offering improved symmetry and reduced pupil banding, suitable for various seat installations and space-constrained environments.
Implementation Method 1
an input region configured to receive and couple light into the optical waveguide
Implementation Method 2
a beam-splitter configured to divide light received from the input region into a first portion and a second portion
Implementation Method 3
a symmetrical diffraction grating comprising a first diffraction grating and a second diffraction grating, each having a symmetry axis, the symmetry axes being perpendicular to each other
Data Source
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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.