Light Guide Element with Multi-Layer Refractive Index for AR Display
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Solution Overview
Problem
In augmented reality glasses, the image sharpness deteriorates when the user moves their visual line or changes the position of their eyes, leading to incomplete observation of the display image.
Innovation Solution
A light guide element with a laminated structure comprising a first and second light guide layer and diffraction elements, where the second layer has a higher refractive index and is thinner, ensuring that the image is properly diffracted and emitted regardless of the user's eye position, using a configuration that includes a cholesteric liquid crystal layer with a helically twisted optical axis and a diffraction period between 0.1 to 10 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional light guide plate is used in AR glasses, then the structure is simple and easy to manufacture, but the image sharpness deteriorates when the user moves their visual line or changes eye position
Solution Approach 1:
The light guide plate is divided into multiple light guide layers with different refractive indices. Each layer has specific optical functions, with higher layers having higher refractive indices. This segmentation allows independent optimization of each layer's optical properties to maintain image sharpness across different viewing positions.
Solution Approach 2:
Different regions of the light guide plate have different optical properties through the multi-layer structure. Each light guide layer is designed with specific refractive index and thickness to control light propagation locally, ensuring consistent image quality regardless of where the user looks.
2Reliability
If the light guide plate uses a single-layer structure, then the manufacturing process is simple, but the image cannot be properly observed when the user moves their visual line
Solution Approach 1:
The light guide plate is divided into multiple light guide layers with different refractive indices. Each layer has specific optical functions, with higher layers having higher refractive indices. This segmentation allows independent optimization of each layer's optical properties to maintain image sharpness across different viewing positions.
Solution Approach 2:
The patent introduces a vertical dimension to the light guide plate structure by stacking multiple layers with different refractive indices. This multi-layer configuration controls light propagation in the thickness direction, ensuring that light reaches the user's eye regardless of horizontal or vertical eye position changes.
3Reliability
If a conventional single-layer light guide plate is used, then the device is compact and simple, but deterioration in image sharpness occurs when the user moves their visual line or eye position
Solution Approach 1:
The light guide plate is divided into multiple light guide layers with different refractive indices. Each layer has specific optical functions, with higher layers having higher refractive indices. This segmentation allows independent optimization of each layer's optical properties to maintain image sharpness across different viewing positions.
Solution Approach 2:
The patent changes the refractive index parameter across different layers, with higher layers having higher refractive indices. This parameter variation optimizes light propagation and total internal reflection at each interface, maintaining image sharpness while keeping the overall structure compact.
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 configuration prevents partial deterioration in image sharpness and allows for the entire image to be suitably observed irrespective of the user's visual line or eye position, ensuring a consistent and clear display.
Implementation Method 1
an incidence diffraction element that is laminated on the second light guide layer of the light guide plate and an emission diffraction element that is laminated on the second light guide layer of the light guide plate
Implementation Method 2
using a configuration that includes a cholesteric liquid crystal layer with a helically twisted optical axis and a diffraction period between 0.1 to 10 μm
Implementation Method 3
a light guide plate that includes a first light guide layer and a second light guide layer... in a case where a refractive index of the first light guide layer is represented by n1 and a refractive index of the second light guide layer is represented by n2... n1<n2
Data Source
AI summary
Provided are: a light guide element in which deterioration in image sharpness can be prevented and the entire area of a display image can be suitably observed irrespective of the visual line of a user, the position of eyes of the user, and the like; and an image display apparatus including the light guide element. The light guide element includes: a light guide plate that includes a first light guide layer and a second light guide layer; and an incidence diffraction element and an emission diffraction element that are laminated on the second light guide layer, in which in a case where a refractive index of the first light guide layer is represented by n1 and a refractive index of the second light guide layer is represented by n2 in the light guide plate, n1<n2 is satisfied.