Holographic Waveguide HUD Using Windscreen Pupil Expansion
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Solution Overview
Problem
Conventional holographic projection systems require complex dielectric stacks to moderate waveguide emissions, which are challenging to manufacture, especially over a broadband of wavelengths, and often result in intensity decreases during waveguiding, affecting image quality.
Innovation Solution
A holographic projector system using a waveguide with partially reflective-transmissive surfaces and a hologram engine that compensates for intensity decreases by modifying the hologram to distribute image content angularly, eliminating the need for complex coatings and allowing the vehicle windscreen to act as a pupil expander.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If complex dielectric stacks are used to moderate waveguide emissions, then emission intensity can be controlled, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The patent extracts the intensity control function from the optical path by modifying the hologram data itself rather than using physical dielectric stacks in the waveguide. The hologram engine pre-compensates for intensity variations by adjusting the amplitude of light directed to different emission zones, eliminating the need for complex manufacturing of graded coatings or dielectric stacks.
Solution Approach 2:
The patent changes the parameter control approach from physical optical properties (dielectric stack composition and thickness) to digital parameters (hologram amplitude values). By modifying the hologram data parameters, the system achieves intensity control without physical manufacturing complexity.
2Device complexity
If conventional waveguide emissions are used without compensation, then system complexity is reduced, but intensity decreases during waveguiding affecting image quality
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-compensating for intensity losses in the hologram engine before light enters the waveguide. The system determines the optimal amplitude for each emission zone in advance, so that when light propagates through the waveguide, the intensity variations are already compensated, maintaining uniform image quality without adding physical compensation mechanisms.
3Illumination intensity
If complex graded coatings are applied to the waveguide output surface, then emission intensity uniformity improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent creates a digital copy or model of the intensity loss profile and compensates for it in the hologram data. Instead of physically applying graded coatings to match the loss profile, the system uses computational modeling to predict and correct intensity variations, replacing physical coating complexity with digital processing.
4Ease of manufacture
If simple waveguide structures are used, then ease of manufacture improves, but intensity compensation capability deteriorates
Solution Approach 1:
The patent replaces the mechanical/optical compensation system (graded coatings, dielectric stacks) with a computational system (hologram engine). The physical waveguide structure remains simple and easy to manufacture, while the intensity compensation function is transferred to the digital domain through hologram amplitude modulation.
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 enables the formation of high-quality holographic reconstructions with uniform intensity across viewing positions, reducing system complexity and cost while maintaining image quality, even with complex windscreen curvature.
Implementation Method 1
A first surface of the pair of parallel reflective surfaces is partially reflective-transmissive so as to form an output comprising a plurality of emission zones for the holographic wavefront
Implementation Method 2
spatially modulate light in accordance with the hologram to form a holographic wavefront
Data Source
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AI summary
A method of head-up display for a vehicle. A first step comprises displaying a hologram of an image on a display device and spatially modulating light in accordance with the displayed hologram to form a holographic wavefront. A second step comprises replicating the holographic wavefront in a first direction using a first pupil expander to form a 1D array of replicas of the holographic wavefront. A third step comprises using a windscreen of the vehicle as a second pupil expander to form a 2D array of replicas of the holographic wavefront from the 1D array of replicas.