Holographic Optical Elements for Multi-Plane HUD Display
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Solution Overview
Problem
Current head-up display systems in aircraft cockpits require pilots to divert their gaze from the external landscape to view non-congruent information, leading to accommodation issues and visual discomfort, as they cannot simultaneously display congruent images at infinity and non-congruent images at a finite distance without causing ocular fatigue.
Innovation Solution
A viewing system utilizing two holographic optical elements that superimpose images of different colors at distinct distances using reflection and transmission properties, allowing for the display of objects at infinity and finite distances without glasses, by employing holographic treatments with specific optical powers tailored for each wavelength, ensuring minimal distortion and ergonomic comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single transparent viewing screen is used to display information, then the information becomes visible without diverting gaze from the external landscape, but the image is mandatorily located on the screen at a finite distance, causing accommodation problems and visual fatigue
Solution Approach 1:
The patent divides the display function into multiple independent layers: a first transparent screen for displaying congruent images at infinity and a second transparent screen for displaying non-congruent images at a finite distance. This segmentation allows each screen to serve its specific function without compromising the other, enabling continuous gaze while eliminating accommodation fatigue by providing separate optical paths for different types of information.
2Measurement precision
If stereoscopic systems are used to display non-congruent images, then vergence problems are solved, but the images are still situated on the screen at a finite distance, and accommodation problems persist along with the need for glasses
Solution Approach 1:
The patent introduces a second transparent viewing screen as an intermediary element positioned between the observer and the first screen. This second screen serves as a dedicated carrier for non-congruent images at a finite distance, allowing the observer to view both congruent and non-congruent information simultaneously without the need for stereoscopic glasses. The intermediary screen resolves the contradiction by providing a separate optical plane that maintains proper vergence-accommodation correspondence.
3Adaptability or versatility
If images are projected at different distances using optical diffusers or shutters, then multi-plane volumetric display is achieved, but the system becomes complex and difficult to integrate into aircraft windscreens
Solution Approach 1:
The patent uses two transparent viewing screens that are optically coupled to project images at different distances. Rather than using complex optical diffusers or moving shutters, the system creates simplified optical copies of the display function using static transparent screens with specific optical properties. This copying approach maintains multi-plane display capability while dramatically reducing system complexity and facilitating integration into aircraft windscreen structures.
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
Enables the simultaneous display of congruent images at infinity and non-congruent images at a finite distance, reducing visual fatigue and accommodation problems, while maintaining acceptable optical and chromatic aberrations, thus enhancing viewing comfort and reducing the need for frequent gaze shifts.
Implementation Method 1
the optical device including two holographic optical elements working by reflection
Implementation Method 2
holographic optical elements making it possible to superimpose, on the outside, two images of different colours at two different distances
Implementation Method 3
the first holographic optical element includes a first holographic treatment having a first optical power reflecting the first wavelength and transmitting the second wavelength
Data Source
AI summary
Viewing systems are provided which include a screen and an optical collimation device including two holographic optical elements working by reflection, the first holographic optical element being closer to the screen, the second holographic optical element being closer to an observer. In the system, the screen displays a first object at a first wavelength and a second object at a second wavelength. Each holographic optical element includes two holographic treatments, each treatment being able to reflect one of the two wavelengths and to transmit the other wavelength. The first holographic element and the second holographic element are arranged such that the image of the first object forms at a first distance from the screen and that the image of the second object forms at a second distance from the screen, different from the first distance.