HUD Light Pipe and Waveguide for Expanded Field of View
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Solution Overview
Problem
Conventional Head-Up Displays (HUDs) are large, expensive, and difficult to fit into smaller aircraft due to their large optical components, which also increase complexity, cost, and reduce brightness and contrast, especially when using dual axis pupil expansion with waveguides.
Innovation Solution
A HUD system utilizing a first light pipe with diffraction gratings or a mirror array for pupil expansion in one direction and a waveguide combiner for expansion in a perpendicular direction, allowing for a compact, high-efficiency system with a larger unvignetted eye box, using an air gap between the light pipe and waveguide to enhance numerical aperture and reduce alignment constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional HUDs use large optical components to form adequate field of view and viewing eye box, then the field of view and eye box are sufficient, but the volume and size become too large to fit within constrained cockpit space
Solution Approach 1:
The patent implements nested waveguide structures where a first waveguide contains a second waveguide, and a third waveguide contains a fourth waveguide. This nesting arrangement allows multiple optical paths and pupil expansion functions to be integrated within a compact volume, achieving large field of view and eye box without proportionally increasing overall HUD size.
Solution Approach 2:
The patent utilizes dual-axis pupil expansion by orienting waveguides in perpendicular directions (first axis and second axis). This dimensional approach allows the system to expand the virtual image space in both horizontal and vertical dimensions, achieving a large unvignetted eye box while maintaining a compact physical footprint through spatial multiplexing.
2Area of stationary object
If conventional HUDs use large optical components, then adequate field of view is achieved, but the cost increases significantly
Solution Approach 1:
The patent replaces traditional mechanical optical components (large lenses, mirrors, and prisms) with integrated waveguide structures that use total internal reflection and diffraction gratings. This substitution eliminates the need for precision-machined large optical elements, reducing manufacturing complexity and cost while achieving the same or better optical performance.
Solution Approach 2:
The patent changes the fundamental operating parameters by using waveguide modal propagation instead of traditional geometric optics. By controlling light through evanescent waves and total internal reflection at waveguide interfaces, the system achieves pupil expansion and field of view control through material properties and geometric configuration rather than large component sizes.
3Area of stationary object
If dual axis pupil expansion with waveguides is used, then eye box size is preserved, but brightness and contrast are adversely affected
Solution Approach 1:
The patent merges multiple waveguide paths and optical functions into an integrated structure where light from a single projector is distributed through nested waveguides. By combining the optical paths and using the waveguide structure to guide and expand the pupil in dual axes simultaneously, the system maintains image brightness and contrast while achieving a large eye box.
4Area of stationary object
If dual waveguides with air gap are used for pupil expansion, then eye box is expanded, but geometric coupling losses are induced
Solution Approach 1:
The patent introduces a turning grating as an intermediary element that couples light between waveguides at an air gap interface. The grating structure provides phase matching and momentum transfer to enable efficient light coupling across the air gap, reducing geometric coupling losses while maintaining the pupil expansion benefits of the dual waveguide configuration.
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 system achieves a larger field of view (up to 72 degrees by 40 degrees) while being smaller and less expensive, with improved brightness and contrast, and easier manufacturing and testing due to separate optical components.
Implementation Method 1
A HUD system utilizing a first light pipe with diffraction gratings or a mirror array for pupil expansion in one direction
Implementation Method 2
a waveguide combiner for expansion in a perpendicular direction
Implementation Method 3
a waveguide combiner configured to expand the pupil in a second direction perpendicular to the first direction
Implementation Method 4
using an air gap between the light pipe and waveguide to enhance numerical aperture and reduce alignment constraints
Data Source
AI summary
A head up display can be used in compact environments. The head up display includes a combiner system including at least one light pipe and a waveguide. The at least one light pipe includes a diffraction grating or mirror array for providing light into the waveguide from the light pipe. The light pipe is configured to receive light and provide first light in a first direction for a first field of view and second light in a second direction for a second field of view. The combiner system can be head worn or stand-alone and can provide dual axis pupil expansion.