Holographic Waveguide HUD With Intensity-Compensated 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 and maintain over a broadband of wavelengths, and struggle with intensity loss during waveguiding, limiting the effectiveness of holographic displays in applications like head-up displays.
Innovation Solution
A system using a waveguide with partially reflective-transmissive surfaces and a hologram engine that compensates for intensity loss by modifying the hologram to distribute light angularly, eliminating the need for complex coatings and allowing the vehicle windscreen to function as a pupil expander, thereby simplifying the display system and maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex dielectric stacks are used to moderate waveguide emissions, then image quality can be maintained, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The patent extracts the complex dielectric stack component from the system and replaces it with a computational approach. The hologram engine calculates and applies intensity compensation directly to the holographic data, eliminating the need for physical dielectric coatings while maintaining image quality control.
Solution Approach 2:
The patent replaces the mechanical/optical system of dielectric stacks with a computational system. The hologram engine uses algorithms to calculate and apply intensity compensation to the holographic data, substituting physical optical components with digital processing.
2Reliability
If conventional waveguide systems are used, then holographic projections can be formed, but intensity loss occurs during waveguiding
Solution Approach 1:
The patent applies preliminary action by calculating and compensating for intensity loss before the light actually propagates through the waveguide. The hologram engine pre-adjusts the holographic data to account for expected intensity decay, ensuring uniform output without requiring physical intensity correction components.
Solution Approach 2:
The system implements a form of feedback by using the known waveguide characteristics (reflectivity, transmission, intensity decay patterns) to inform the hologram calculation process. The hologram engine continuously adjusts the holographic data based on modeled feedback from waveguide performance.
3Illumination intensity
If dielectric stacks with varying thickness are used to compensate for intensity loss, then uniform emission can be achieved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces the mechanical solution of varying coating thickness with a computational approach. Instead of physically adjusting dielectric layer thickness across the waveguide surface, the hologram engine digitally adjusts the holographic data to compensate for intensity variations, achieving uniform emission without complex manufacturing.
Solution Approach 2:
The patent changes the parameter being controlled from physical coating thickness to digital intensity values in the holographic data. By modifying the computational parameters rather than physical dimensions, the system achieves intensity uniformity while avoiding the manufacturing complexity of precision variable-thickness coatings.
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 creation of high-quality holographic projections with uniform intensity across a wide viewing area without the need for complex coatings, reducing system complexity and cost while maintaining image quality and coherence across the visible spectrum.
Implementation Method 1
The waveguide comprising a pair of parallel reflective surfaces arranged to waveguide the diffracted light field therebetween
Implementation Method 2
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 or replication zones for the diffracted light field
Implementation Method 3
The diffractive pattern may be arranged to angularly distribute light within the diffracted light field in accordance with spatial position within the image such that continuous angular ranges (i.e. angular channels) of the diffracted light field respectively correspond with continuous regions of the image
Data Source
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.