Optical Laminate for AR Displays with Large Diffraction Angle
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Solution Overview
Problem
Existing optical elements for augmented reality glasses face challenges in achieving a large diffraction angle, leading to reduced light guide efficiency due to limitations in manufacturing and alignment of liquid crystal molecules, which results in light leakage and decreased performance.
Innovation Solution
A layered structure comprising a first optically-anisotropic layer, a phase difference layer, and a patterned cholesteric liquid crystal layer, where the layers are aligned to achieve a continuous rotation of the optical axis, allowing for a larger diffraction angle without the need for reducing the period of liquid crystal alignment, thereby improving manufacturing feasibility and light guide efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the period of alignment directions of liquid crystal molecules is decreased to increase diffraction angle, then a larger diffraction angle can be obtained, but manufacturing becomes difficult
Solution Approach 1:
The patent introduces a phase difference layer to create a three-layer structure (optically-anisotropic layer + phase difference layer + patterned cholesteric liquid crystal layer). This dimensional expansion allows the system to achieve large diffraction angles through the combined optical effects of multiple layers rather than relying solely on reducing the alignment period in a single layer, thus avoiding manufacturing difficulties.
Solution Approach 2:
The patent combines three different optical layers with distinct functions: an optically-anisotropic layer for initial light modulation, a phase difference layer for phase control, and a patterned cholesteric liquid crystal layer for selective reflection. This composite structure achieves superior optical performance (large diffraction angle) while maintaining manufacturability, as each layer can be optimized and fabricated independently according to its specific requirements.
2Device complexity
If a single-layer optical element is used to achieve diffraction, then the structure is simple, but the diffraction angle is insufficient and light guide efficiency decreases
Solution Approach 1:
The patent merges three functional layers into a unified optical element where each layer contributes to light manipulation. The optically-anisotropic layer, phase difference layer, and patterned cholesteric liquid crystal layer work synergistically to achieve high diffraction angles and prevent light leakage, thereby improving light guide efficiency while distributing the functional requirements across multiple specialized components.
Solution Approach 2:
By transitioning from a single-layer to a three-layer structure, the patent adds dimensional complexity to the optical path control. This multi-layer architecture enables precise control over light phase, polarization, and direction, achieving high light guide efficiency through coordinated interaction between layers rather than relying on a single complex layer.
3Adaptability or versatility
If the reflecting surface is made non-parallel to the incidence surface to change reflection direction, then light can be reflected at different angles, but the diffraction angle cannot be sufficiently increased
Solution Approach 1:
The patent changes the optical parameters of the system by introducing a phase difference layer with specific phase retardation characteristics. This allows control over the diffraction angle through optical parameter adjustment (phase difference, birefringence) rather than relying solely on geometric configuration (surface angles), enabling larger diffraction angles while maintaining the reflecting surface configuration.
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 proposed solution enables a significant increase in diffraction angle, enhancing light guide efficiency by preventing light leakage and improving the overall performance of AR display devices.
Implementation Method 1
light is diffracted (refracted) using a diffraction element to be incident into one end portion of a light guide plate
Implementation Method 2
a first optically-anisotropic layer that is formed of a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound continuously rotates
Implementation Method 3
a patterned cholesteric liquid crystal layer that is formed of a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound continuously rotates
Implementation Method 4
the liquid crystal compound being cholesterically aligned
Implementation Method 5
a phase difference layer
Implementation Method 6
it is difficult to cause light to be incident at an angle where the light is totally reflected in the light guide plate
Data Source
AI summary
Provided are an optical laminate in which a large diffraction angle can be obtained, a light guide element, and an AR display device. The optical laminate includes, in the following order: a first optically-anisotropic layer that is formed of a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound continuously rotates in at least one in-plane direction; a phase difference layer; and a patterned cholesteric liquid crystal layer that is formed of a composition including a liquid crystal compound and has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound continuously rotates in at least one in-plane direction, the liquid crystal compound being cholesterically aligned, in which in the first optically-anisotropic layer and the patterned cholesteric liquid crystal layer, the one in-plane directions in which the direction of the optical axis derived from the liquid crystal compound continuously rotates are the same, and rotation directions of the direction of the optical axis derived from the liquid crystal compound in the one in-plane direction are the same.