Waveguide Pupil Expander for Wider HUD Eye-Box and Field of View
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Solution Overview
Problem
Existing display systems face limitations in expanding the range of angles of light rays that can propagate through an eye's pupil to form an image, particularly in configurations where the projection distance is significantly larger than the display device's aperture, resulting in a small field of view and limited eye movement.
Innovation Solution
A system utilizing waveguide pupil expanders to replicate and expand the exit pupil in two dimensions, using elongated and planar waveguides to increase the field of view and eye-box size by creating replicas of the light field, allowing for larger eye movement and improved image perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional pupil expansion systems are used for diffracted light fields, then the system structure is relatively simple, but the eye-box area and field of view are limited
Solution Approach 1:
The patent transitions from conventional one-dimensional pupil expansion to two-dimensional pupil expansion by stacking multiple waveguide layers. Each waveguide layer expands the pupil in a different dimension, collectively achieving a two-dimensional expansion of the eye-box area. This dimensional approach allows significant increase in viewing area without proportionally increasing system complexity.
Solution Approach 2:
The patent employs a nested structure where multiple waveguide pupil expander layers are stacked together, with each layer containing opposing surfaces and internal reflection structures. The waveguides are arranged in a nested configuration where light propagates through successive layers, with each layer contributing to the overall pupil expansion. This nesting allows compact integration of multiple expansion functions.
2Adaptability or versatility
If the range of light ray angles is increased to expand field of view, then the field of view improves, but the eye movement control becomes more difficult
Solution Approach 1:
The patent segments the pupil expansion function into multiple discrete waveguide layers, each handling a specific angular range or portion of the pupil expansion. By dividing the overall expansion task across multiple segments, each layer can be optimized for its specific function, making the overall system more manageable and controllable despite the expanded field of view.
Solution Approach 2:
The waveguide structures act as intermediaries that systematically redirect and control light rays across different angles. The internal reflection surfaces within each waveguide layer serve as intermediary elements that gradually steer light through controlled reflections, providing smooth transition and control over the expanded angular range without requiring direct manipulation of all rays.
3Speed
If waveguide pupil expanders are used to replicate exit pupil, then the angular range and field of view increase, but the device complexity increases
Solution Approach 1:
The patent achieves pupil expansion by changing key optical parameters within the waveguide structures, including the angle of internal reflection, the refractive index of waveguide materials, and the spacing between opposing surfaces. By systematically adjusting these parameters across multiple layers, the system expands the angular range of light propagation while maintaining manageable structural complexity through parameter optimization rather than structural complexity.
Solution Approach 2:
Each waveguide pupil expander layer is designed as a universal component that performs multiple functions: it expands the pupil in a specific dimension, controls light propagation angles, and maintains image quality. The opposing surfaces within each waveguide serve universal purposes of both reflection and structural support. This multi-functionality reduces the need for separate specialized components, thereby managing overall device 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 enlarges the viewing area and field of view, enabling improved image perception and eye movement, suitable for applications like automotive head-up displays with compact and streamlined design.
Implementation Method 1
A system utilizing two-dimensional waveguide pupil expanders, each with opposing surfaces, to replicate and expand the exit pupil, allowing for increased angular range and field of view by internal reflection
Data Source
AI summary
A display system comprises a waveguide forming a pupil expander. The waveguide comprises a pair of opposing surfaces arranged to guide a diffracted light field therebetween by internal reflection. An input port of the waveguide is arranged to receive light from a display system. An output port of the waveguide is formed by a first transmissive-reflective element of a first surface of the pair of opposing surfaces. The first transmissive-reflective element is such that the diffracted light field is divided at each internal reflection and a plurality of replicas of the diffracted light field are transmitted out of the waveguide through the output port. The input port comprises a second transmissive-reflection element arranged to receive at least a portion of the light from the display system.