Optical Waveguide Holograms for Variable Projection-Distance Displays
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Solution Overview
Problem
Conventional head-up displays have limited eyebox sizes, restricting viewer seating positions and are inadequate for both traditional displays and augmented reality applications due to fixed projection distances.
Innovation Solution
An apparatus with an optical waveguide and an optical element featuring volume holograms allows for variable projection distances, enabling simultaneous display of images at near and far ranges, and is switchable to adapt to viewer position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed projection distance is used in conventional head-up displays, then the display is simple to implement, but it cannot accommodate both traditional displays and augmented reality applications simultaneously
Solution Approach 1:
The patent applies a switchable focusing element that can dynamically change the projection distance of the virtual image. This element allows the system to switch between different focusing states, enabling the display to adapt between traditional close-range displays and augmented reality far-range displays, thereby resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The patent changes the optical parameter of the focusing element to alter the projection distance. By modifying the focusing state of the switchable focusing element, the system can adjust the image plane position between near and far ranges, enabling versatile application without requiring multiple separate optical systems.
2Ease of operation
If the eyebox size is enlarged to allow more seating positions, then viewer flexibility improves, but the optical unit size increases
Solution Approach 1:
The patent uses an optical fiber to couple light from the imaging unit, which expands the exit pupil in the longitudinal dimension. This dimensional expansion allows the eyebox to be enlarged without proportionally increasing the lateral area of the optical unit, thus improving viewer seating flexibility while controlling optical unit size.
3Adaptability or versatility
If a single projection distance is used, then the optical system is simple, but it cannot provide both near-range traditional displays and far-range augmented reality displays
Solution Approach 1:
The patent employs a switchable focusing element that provides multi-functionality within a single optical system. This element enables the same optical path to serve both traditional near-range displays and augmented reality far-range displays, eliminating the need for separate optical systems while maintaining versatility.
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 flexible image projection distances for traditional and augmented reality applications, enhancing viewer flexibility and reducing display errors by adjusting to different viewing positions.
Implementation Method 1
The optical waveguide causes light coming from an imaging unit, which is incident through a first light incidence surface, to undergo repeated internal reflection to move in a first direction away from the first light incidence surface
Implementation Method 2
The optical element has at least two volume holograms arranged side by side, by means of which displays in a near range and in a far range can be superimposed simultaneously
Data Source
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AI summary
The invention relates to an apparatus for generating a virtual image. Said apparatus comprises at least one imaging unit (1) for generating the image and an optical waveguide for widening an exit pupil. The optical waveguide (5) comprises a decoupling area (521). An optical element (70) for influencing a projection distance for at least one sub-region of the virtual image (VB) is arranged adjacent to the decoupling region (521).