Optical Element Diffraction Layout for Wide-FOV, Low-Crosstalk AR Displays
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Solution Overview
Problem
Existing augmented reality (AR) glasses face challenges in achieving a wide field of view (FOV) without increasing size and weight by using multiple light guide plates, and suffer from crosstalk issues when using a single light guide plate to enhance FOV.
Innovation Solution
An optical element with a light guide plate, incidence portion, and emission portion, utilizing diffraction elements with specific period ratios and angles, and a liquid crystal diffraction layer to prevent crosstalk and enhance FOV using one light guide plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light guide plates are used to display full color images, then color display capability is improved, but device size and weight increase
Solution Approach 1:
The patent combines multiple light guide plates (red, green, blue) into a single integrated light guide plate structure. The incidence portion and emission portion are merged into one component, and the diffraction elements are integrated within the same plate, reducing the overall number of components while maintaining full color display capability through wavelength-specific diffraction regions.
2Weight of moving object
If the number of light guide plates is reduced to one, then device size and weight are reduced, but crosstalk occurs in the displayed image
Solution Approach 1:
The patent applies local quality by creating distinct diffraction regions within the single light guide plate, each optimized for specific wavelengths. The incidence portion contains diffraction elements tuned for red, green, and blue light entry, while the emission portion has corresponding regions for each color. This localized optimization prevents crosstalk by ensuring each wavelength is diffracted and emitted at the correct position without interfering with other colors.
Solution Approach 2:
The light guide plate is segmented into multiple functional regions: an incidence portion with wavelength-specific diffraction elements for entering light, and an emission portion with corresponding diffraction regions for exiting light. Each region is designed to handle specific wavelengths independently, preventing crosstalk while maintaining full color capability in a single plate structure.
3Volume of moving object
If a wide field of view is achieved using one light guide plate, then device compactness is improved, but crosstalk and image blurring increase
Solution Approach 1:
The patent expands the field of view by utilizing the planar surface area of the light guide plate rather than increasing volume. The incidence and emission portions are arranged to cover wide angular ranges across the plate surface, allowing light to enter and exit at multiple angles. This two-dimensional expansion achieves wide FOV while maintaining a compact, thin profile and preventing crosstalk through the localized diffraction region design.
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
The solution enables wide FOV in AR glasses with reduced crosstalk, allowing for clear image display without blurring or double images.
Implementation Method 1
light (projection light) projected from a display is diffracted (refracted) using a diffraction element to be incident into one end part of a light guide plate. As a result, the light is introduced into the light guide plate at an angle such that the light is totally reflected and propagates in the light guide plate.
Implementation Method 2
the light is introduced into the light guide plate at an angle such that the light is totally reflected and propagates in the light guide plate
Implementation Method 3
The light propagating in the light guide plate is also diffracted by the diffraction element in the other end part of the light guide plate and is emitted from the light guide plate to an observation position by the user.
Data Source
AI summary
An optical element includes a light guide plate, an incidence portion, and an emission portion, in which the incidence/emission portion includes an Λ1 diffraction element having a diffraction period Λ1, an Λ2 diffraction element having a diffraction period Λ2, and an Λ3 diffraction element having a diffraction period Λ3, “Λ1:Λ2:Λ3=1:1√2±0.015:1/2±0.015” is satisfied, an angle between periodic directions of the Λ1 diffraction element and the Λ2 diffraction element and an angle between periodic directions of the Λ2 diffraction element and the Λ3 diffraction element is 45° or 135° (±0.5°), and an angle between the periodic directions of the Λ2 diffraction elements in the incidence portion and the emission portion is any one of 0°, 90°, 180°, or 270° (±0.5°).