Tapered Waveguide Pupil Expander for HUD Eye-Box
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional display systems face limitations in projecting holographic images due to the restricted range of angles of light that can propagate through the eye's pupil, leading to a small field of view and limited eye movement without losing the image, especially in head-up displays where the projection distance is significantly greater than the display device's aperture.
Innovation Solution
A pupil expansion system using a pair of elongated and tapered waveguides that replicate the pupil in one dimension, allowing for a larger eye-box and increased field of view by dividing and redirecting the diffracted light field, enabling the viewer to move their head while maintaining the image visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional display systems are used to project holographic images, then the projection distance can be significantly greater than the display device's aperture, but the field of view is limited and eye movement is restricted without losing the image
Solution Approach 1:
The waveguide is divided into multiple waveguide sections, each with different optical power, to segment the light propagation path and expand the pupil in different directions, thereby increasing the field of view while maintaining projection distance
Solution Approach 2:
The system expands the pupil not only in the lateral direction but also in the depth direction by using multiple waveguide sections with different optical powers, adding a dimensional aspect to pupil expansion that increases adaptability for eye movement
2Device complexity
If a single waveguide is used for pupil expansion, then the device complexity is reduced, but the eye-box size and field of view are limited
Solution Approach 1:
Multiple waveguide sections are merged into a single integrated waveguide structure that provides cumulative pupil expansion, combining the functions of multiple expanders while maintaining a unified device structure that manages complexity
3Adaptability or versatility
If the pupil is expanded to increase field of view, then eye movement freedom is improved, but the optical system complexity increases
Solution Approach 1:
Each waveguide section serves multiple functions: it expands the pupil in a specific direction, relays light from the previous section, and contributes to the overall field of view expansion, making the optical system more efficient despite increased complexity
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 effectively increases the eye-box size and field of view, allowing for greater viewer movement and improved image perception in head-up displays by expanding the pupil and redirecting diffracted light, enhancing the viewing experience with a compact and efficient design.
Implementation Method 1
Each waveguide comprises a pair of reflective surfaces arranged to provide waveguiding of input light therebetween
Implementation Method 2
The image is formed by illuminating a diffractive pattern (e.g., hologram) displayed on the display device
Data Source
AI summary
A pupil expander for a head-up display. The head-up display has an eye-box having a first dimension and second dimension. The pupil expander comprises a pair of first waveguides each arranged to replicate a pupil in the first dimension of the eye-box. Each waveguide is elongated and tapered in the direction of elongation such that its input end is narrower than its output end. The first waveguides are arranged so that their input ends are substantially proximate each other and their respective output ends are substantially distal from each other.