HUD Light Pipe Waveguide Pupil Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Head-Up Displays (HUDs) are too large and expensive for smaller aircraft, requiring large optical components that are difficult to align and integrate, leading to size, weight, and cost issues, as well as reduced brightness and contrast due to air gaps and geometric coupling losses in pupil expansion systems.
Innovation Solution
A compact HUD system utilizing a catadioptric optical system with a polarizing beam splitter, field lens with diffractive surface, and a waveguide combiner, which includes a turning grating or mirror array for pupil expansion, reducing the need for corrector lenses and fold optics, and enhancing color correction and aberration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional HUD optical components are used, then adequate field of view and viewing eye box are achieved, but the device size and volume become too large for smaller aircraft cockpits
Solution Approach 1:
The patent embeds the HUD optical system within the aircraft windshield structure, nesting the combiner and optical components into the existing windshield assembly. This eliminates the need for separate external HUD housings and reduces overall device volume while maintaining adequate field of view through integrated optical paths.
Solution Approach 2:
The patent employs waveguide technology that expands the optical path in the z-dimension (depth) rather than requiring lateral expansion in the x-y plane. By using total internal reflection and grating-based light manipulation within a thin waveguide layer, the system achieves a large field of view without proportionally increasing the device's footprint volume.
2Area of stationary object
If conventional HUD optical components are used, then adequate field of view is achieved, but the device becomes difficult to align and integrate
Solution Approach 1:
The patent combines multiple optical functions (combiner, beam splitter, waveguide, and collimation elements) into a single integrated windshield assembly. This merging of functions eliminates the need for separate alignment of multiple discrete optical components, as the integrated structure provides fixed geometric relationships between all optical elements.
Solution Approach 2:
The waveguide-based optical system uses the windshield's own structure and geometry to define optical paths. The windshield thickness, refractive index, and surface orientations automatically determine light propagation paths through total internal reflection and grating diffraction, eliminating the need for external alignment mechanisms or adjustable mounting systems.
3Area of stationary object
If pupil expansion systems with air gaps are used, then viewing eye box is increased, but brightness and contrast are reduced due to geometric coupling losses
Solution Approach 1:
The patent uses a thin waveguide film with embedded gratings to expand the pupil without requiring air gaps. The waveguide's continuous solid structure maintains optical coupling throughout the light path, preventing the geometric coupling losses that occur at air-glass interfaces while still achieving pupil expansion through controlled total internal reflection and grating diffraction.
Solution Approach 2:
The patent employs a composite waveguide structure combining high-refractive-index glass or polymer material with embedded diffraction gratings. This composite design enables pupil expansion through the grating patterns while maintaining continuous optical coupling within the solid material, avoiding the brightness and contrast penalties associated with air gaps in conventional pupil expansion 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 solution results in a significantly smaller, lighter, and more cost-effective HUD system with improved brightness and contrast, capable of providing a wide field of view in constrained cockpit spaces while maintaining image quality and efficiency.
Implementation Method 1
a polarizing beam splitter having a first face, a second face, and a third face. The field lens is disposed to provide light to the first face, and the polarizing beam splitter is configured to reflect light of a first polarization toward the second face
Implementation Method 2
The field lens has a diffractive surface for increasing power of the field lens and providing color correction
Implementation Method 3
a waveguide combiner configured to expand the pupil in a second direction perpendicular to the first direction, wherein the at least one turning grating or mirror array provides light into the waveguide from the light pipe
Implementation Method 4
The first light pipe is configured to expand a pupil in a first direction and includes at least one turning grating or mirror array
Implementation Method 5
Light from the image source enters the beam splitter and is reflected toward the collimating mirror. The light striking the collimating mirror is reflected through the polarizing beam splitter toward a combiner
Implementation Method 6
A compact HUD system utilizing a catadioptric optical system with a polarizing beam splitter, field lens with diffractive surface
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 turning grating or mirror array for providing light into the waveguide from the light pipe. An additional light pipe can also be provided. The combiner system can be headworn or stand-alone and can provide dual axis pupil expansion.