Waveguided Hologram HUD for Eye-Box Expansion and Detection
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Solution Overview
Problem
Conventional holographic projection systems face limitations in expanding the eye-box size and operating range of head-up displays, particularly in vehicles, due to angular restrictions and intensity decreases with propagation distance, which affect the quality and visibility of holographic images.
Innovation Solution
The use of a waveguide with opposing reflective surfaces to replicate and expand both the holographic wavefront for image formation and a second wavefront for object detection, allowing for increased eye-box size and operating range by creating multiple replicas of the light patterns that propagate along different optical paths, providing high temporal resolution and inherent compensation for intensity decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional holographic projection system is used, then the system structure is simple, but the eye-box size is limited and the operating range is restricted due to angular restrictions and intensity decreases with propagation distance
Solution Approach 1:
The waveguide is divided into multiple reflective surfaces that create separate optical paths for different replicas of the holographic wavefront. Each reflective surface segment contributes to forming a specific replica, allowing the eye-box to be expanded by distributing light through multiple segmented paths rather than a single path
Solution Approach 2:
The patent introduces multiple optical paths as an additional dimension to the single propagation path. By creating replicas that travel along different optical paths with varying lengths, the system expands the effective eye-box size in the spatial domain while maintaining image quality through the multi-dimensional light distribution
2Length of stationary object
If the propagation distance is increased to expand the operating range, then the operating range is improved, but the intensity of the holographic image decreases
Solution Approach 1:
The waveguide structure preliminarily distributes and directs light through multiple reflective surfaces before the light reaches the viewing area. This preliminary action ensures that light intensity is maintained across different propagation distances by creating multiple replicas that can be optimized for their respective path lengths
Solution Approach 2:
The patent changes the optical path length parameter for different replicas, allowing each replica to be optimized for specific propagation distances. By varying the path length parameter across different reflective surfaces, the system maintains intensity while extending the operating range
3Area of stationary object
If multiple replicas of the light pattern are created to expand the eye-box, then the eye-box size is increased, but the system complexity increases
Solution Approach 1:
The waveguide structure serves multiple functions simultaneously: it guides the holographic wavefront, creates multiple replicas, expands the eye-box, and maintains image intensity. This multi-functionality reduces the need for separate components that would otherwise be required to achieve each of these effects independently
4Length of stationary object
If the propagation distance is increased, then the operating range is expanded, but the temporal resolution for object detection decreases
Solution Approach 1:
The detection process is segmented into multiple parallel channels, each corresponding to a different replica with a specific optical path length. This segmentation allows simultaneous detection at multiple time points, maintaining temporal resolution while extending the operating range through the distribution of detection events across different time intervals
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
This solution enhances the quality and visibility of holographic images by increasing the eye-box size and operating range, enabling a larger area for object detection with high temporal resolution and reduced need for precise intensity compensation, effectively addressing the limitations of conventional systems.
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
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 holographic wavefront and second wavefront
Data Source
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AI summary
A head-up display for a vehicle. The head-up display comprises 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. The first wavefront is a first holographic wavefront formed by illuminating a first hologram of a picture. The second light engine is arranged to form a second wavefront. The waveguide comprising an input, pair of opposing, reflective surfaces; and an output. The input is arranged to receive the first holographic wavefront and second wavefront. 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 holographic wavefront and second wavefront. The eye-box for a viewer receives the first holographic wavefront. The viewer forms a first holographic image of the picture, that appears in a region between the first hologram and eye-box, from the first holographic wavefront. The second wavefront forms a light pattern in the region. The light detector is arranged to receive a light return of the light pattern if an object is present in the region.