Holographic Waveguide Eye-Box Expansion for Vehicle HUDs
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Solution Overview
Problem
Conventional head-up displays have limited eye-box size and operating range, restricting the angular view and detection capabilities, especially when the holographic image is formed downstream of the hologram and the display device is small, leading to significant angular restrictions.
Innovation Solution
A waveguide system is used to replicate and expand the eye-box and detection system by internal reflection between opposing reflective surfaces, allowing multiple replicas of the holographic wavefront for object detection, which increases the illuminated area and provides high temporal resolution without requiring precise intensity compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small display device is used to form holographic images downstream, then the device size is reduced, but the angular view and eye-box size are significantly restricted
Solution Approach 1:
The patent introduces a waveguide component that adds a new dimensional aspect to light propagation. By guiding light through a waveguide structure with multiple internal reflections, the system expands the angular view and eye-box size without increasing the physical footprint of the display device. The waveguide creates multiple optical paths that diverge to illuminate different angular positions, effectively trading propagation distance in the waveguide for angular coverage.
Solution Approach 2:
The waveguide acts as an intermediary between the small display device and the viewer's eye. It receives the holographic wavefront from the compact display device and distributes it across multiple angular positions through internal reflections. This intermediary structure enables a small display device to achieve the angular coverage and eye-box size that would otherwise require a much larger direct display system.
2Adaptability or versatility
If the holographic image is formed downstream of the hologram, then the image formation flexibility is improved, but the angular restrictions are significantly increased
Solution Approach 1:
The waveguide introduces an additional spatial dimension for light propagation, allowing the system to form holographic images downstream while compensating for angular restrictions. By utilizing the waveguide's length and multiple internal reflections, the system creates divergent optical paths that restore the angular view range even when the image is formed at a downstream position.
3Measurement precision
If multiple replicas of the wavefront are created for object detection, then the illuminated area and temporal resolution are improved, but the system complexity increases
Solution Approach 1:
The waveguide system performs multiple functions simultaneously: it expands the eye-box for holographic display, creates multiple replicas for object detection, and provides temporal resolution for detection. By integrating these functions into a single waveguide structure, the system achieves multi-functionality without proportionally increasing complexity. The same internal reflection mechanism that expands the eye-box also creates the multiple replicas needed for detection.
Solution Approach 2:
The patent merges the holographic display function and the object detection function into a single integrated system. The waveguide simultaneously delivers the holographic wavefront to the eye-box and creates replicas for object detection in the same optical path. This merging of functions reduces the overall system complexity compared to having separate systems for display and detection.
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 waveguide system effectively expands the eye-box and detection range, enabling a larger angular view and improved temporal resolution for object detection, even with small display devices, by replicating the holographic wavefront and forming multiple replicas with different optical paths.
Implementation Method 1
The pair of opposing reflective surfaces is arranged to waveguide the first holographic wavefront and second wavefront therebetween by internal reflection
Implementation Method 2
The light detector is arranged to receive a light return of the light pattern (only) if an object is present in the region. A 'light return' means detection of scattered or reflected light of the light pattern
Data Source
AI summary
Embodiments include systems and methods for operating a head-up display for a vehicle. Embodiments include a first light engine, a second light engine, at least one waveguide, an eye-box for a viewer, and a light detector. The first light engine is arranged to form a first wavefront (e.g., a first holographic wavefront) formed by illuminating a first hologram of a picture, and the second light engine is arranged to form a second wavefront. The waveguide includes an input, pair of opposing reflective surfaces, and an output. The input is arranged to receive the first and second holographic wavefronts. The pair of opposing reflective surfaces is arranged to waveguide the first holographic wavefront and second wavefront therebetween by internal reflection. A first surface of the pair of opposing reflective surfaces is partially transmissive thereby forming an output port for a plurality of replicas of the first and second holographic wavefronts.