Holographic Optical Element Eye Box Expansion via Guide Image Segmentation
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Solution Overview
Problem
Augmented reality (AR) glasses using holographic optical elements (HOE) face challenges in providing a large enough eye box for accurate image viewing, as the retinal projection method results in a very small focused region, making it difficult for general viewers to accurately position their eyes.
Innovation Solution
The image display device includes a main light source, a display panel, a holographic optical element (HOE), and optical systems that diffract light to generate both a main image and a guide image. The guide image surrounds the main image, created by light incident along different paths, facilitating easier alignment of the viewer's eyes with the eye box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a holographic optical element (HOE) is used as the combiner to implement complex optical characteristics in a simple form, then the device complexity is reduced, but the eye box size becomes very small making it difficult for general viewers to accurately position their eyes
Solution Approach 1:
The patent segments the optical system into multiple HOEs: a first HOE for forming the main image and a second HOE for forming the guide image. This segmentation allows each HOE to have optimized functions, with the second HOE specifically dedicated to expanding the eye box through guide image formation, thereby resolving the contradiction between device simplicity and eye box size.
Solution Approach 2:
The patent introduces a guide image as an intermediary element between the viewer's eye and the main image. This guide image, formed by the second HOE, serves as a visual indicator that helps viewers locate and align with the eye box, effectively mediating the interaction between the user and the optical system without adding mechanical complexity.
2Device complexity
If the HOE focuses the image directly on the viewer's eyes using retinal projection, then the optical system is simplified, but the region on which the image is focused becomes very small requiring accurate eye positioning
Solution Approach 1:
The optical system is segmented into two functional parts: the first HOE maintains the retinal projection function for main image formation, while the second HOE is added specifically for guide image formation. This segmentation preserves the simplicity of the original optical system while adding the capability to ease eye positioning through the guide image.
Solution Approach 2:
The patent employs different colors for the main image and guide image (the guide image can be displayed in a color different from the main image). This color differentiation makes the guide image easily distinguishable, helping viewers quickly identify and align with the eye box without requiring complex mechanical adjustment mechanisms.
3Area of stationary object
If a beam splitter and optical system are combined as the combiner, then the eye box can be made larger, but the device complexity and size increase significantly
Solution Approach 1:
The patent changes the key parameter of the combiner from a beam splitter (which requires large physical size and complex alignment) to a holographic optical element. By utilizing the diffraction properties and interference patterns of HOEs, the system achieves eye box expansion through optical parameter manipulation rather than mechanical size increase, thereby reducing device complexity while maintaining functional performance.
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 allows viewers to easily identify and align with the eye box by providing a larger guide image, improving the usability and effectiveness of AR glasses with HOE technology.
Implementation Method 1
a holographic optical element (HOE) configured to diffract the first light emitted from the display panel to make the first light travel to a first region to generate a main image
Implementation Method 2
a first optical system provided on a traveling path of the first light between the main light source and the HOE, the first optical system being configured to change the traveling path of the first light to be incident on the HOE along a first path
Implementation Method 3
a second optical system provided on a traveling path of the second light, the second optical system being configured to change a traveling path of the second light to be incident on the HOE along a second path different from the first path
Data Source
AI summary
An image display device includes a main light source configured to emit a first light; a display panel configured to modulate the first light to add image information to the first light; a holographic optical element (HOE) configured to diffract the first light emitted from the display panel to make the first light travel to a first region to generate a main image; a first optical system provided on a traveling path of the first light between the main light source and the HOE, the first optical system being configured to change the traveling path of the first light to be incident on the HOE along a first path; an auxiliary light source configured to emit a second light; and a second optical system provided on a traveling path of the second light, the second optical system being configured to change a traveling path of the second light to be incident on the HOE along a second path different from the first path.