Cholesteric Liquid Crystal Layer for AR Light Guidance

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Solution Overview

Problem

Current optical elements for AR glasses primarily reflect incident light rather than diffracting specific circularly polarized light in a specific wavelength range, limiting their ability to efficiently guide light into light guide plates.

Innovation Solution

A cholesteric liquid crystal layer with a liquid crystal alignment pattern where the optical axis direction continuously rotates in one in-plane direction, and bright and dark portions are tilted at 80° or more with respect to the main surface, allowing for selective diffraction of specific circularly polarized light through transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a cholesteric liquid crystal layer is used for reflection, then light can be reflected with selective wavelength, but light cannot be efficiently diffracted into light guide plates at required angles

Engineering Contradiction:

Improvelight guidance efficiencyVSAvoiddiffraction function

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent combines the reflection function and diffraction function into a single cholesteric liquid crystal layer. The layer simultaneously provides selective wavelength reflection through its helical structure and angle-dependent diffraction through its tilted periodic pattern, eliminating the need for separate optical elements and improving overall light guidance efficiency into the light guide plate

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cholesteric liquid crystal layer is designed to perform multiple optical functions: it reflects specific wavelengths of light, diffracts light at controlled angles, and guides light into the light guide plate. This multi-functional design replaces traditional single-function optical elements and improves system versatility

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If a reflective cholesteric liquid crystal structure is used, then circularly polarized light can be selectively reflected, but the structure cannot transmit and diffract light effectively

Engineering Contradiction:

Improvetransmission diffraction capabilityVSAvoidlight transmission efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

Instead of using the traditional reflective mode of cholesteric liquid crystal layers, the patent inverts the optical interaction by designing the layer to transmit and diffract light through its periodic structure. The tilted periodic pattern creates angle-dependent transmission diffraction, allowing circularly polarized light to be effectively diffracted while transmitting through the layer rather than being reflected

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of operation

If light is incident at normal direction to a cholesteric liquid crystal layer, then reflection occurs, but light cannot be introduced into light guide plate at required angle

Engineering Contradiction:

Improvelight incident simplicityVSAvoidlight propagation angle

Core Design Contradiction:

Ease of operationVSShape

Solution Approach 1:

The patent changes the geometric parameters of the cholesteric liquid crystal layer by introducing a tilted periodic pattern with a specific tilt angle. This parameter change transforms the optical interaction from normal reflection to angle-dependent transmission diffraction, enabling light to be diffracted at the required angle for efficient coupling into the light guide plate while maintaining simple normal incidence

Inventive Principle:

Principle #35Parameter changes

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 the formation of a transmission-type liquid crystal diffraction element that effectively diffracts specific circularly polarized light in a specific wavelength range, improving light guidance into light guide plates for AR glasses.

Implementation Method 1

incident circularly polarized light is diffracted by the cholesteric liquid crystal layer such that the circularly polarized light can be reflected in a state where it is tilted with respect to an incidence direction

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

A cholesteric liquid crystal layer that is obtained by immobilizing a cholesteric liquid crystalline phase

Methodology Applied

Scientific EffectCholesteric liquid crystal reflection: Cholesteric Liquid Crystal

Data Source

PatentUS11782196B2Cholesteric liquid crystal layer and method for forming cholesteric liquid crystal layer

Publication Date: 2023.10.10 FUJIFILM CORP

AI summary

Provided are a cholesteric liquid crystal layer that diffracts specific circularly polarized light in a specific wavelength range by transmission, and a method of forming the cholesteric liquid crystal layer. The cholesteric liquid crystal layer is obtained by immobilizing a cholesteric liquid crystalline phase, in which the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one in-plane direction, in a cross-section of the cholesteric liquid crystal layer observed with a scanning electron microscope, bright portions and dark portions derived from the cholesteric liquid crystalline phase are tilted at 80° or more with respect to a main surface of the cholesteric liquid crystal layer.