Patterned Cholesteric Liquid Crystal Element for Uniform Brightness
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Solution Overview
Problem
In augmented reality glasses, the brightness of light emitted from a light guide plate is non-uniform due to uniform diffraction efficiency in the liquid crystal diffraction element, and the use of cholesteric liquid crystal layers results in reduced light reflection and blue shift issues.
Innovation Solution
An optical element with a patterned cholesteric liquid crystal layer having a liquid crystal alignment pattern where the optical axis direction continuously rotates in a plane, featuring varying helical structures and pitches, ensuring uniform brightness and enhanced light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a liquid crystal diffraction element with uniform diffraction efficiency is used, then light can be diffracted into the light guide plate, but the brightness of emitted light becomes non-uniform
Solution Approach 1:
The patent applies local quality by making the diffraction efficiency spatially non-uniform across the diffraction element. Specifically, the diffraction efficiency is designed to be higher at the center region and lower at the peripheral regions, which compensates for the natural light distribution pattern and achieves uniform overall brightness in the emitted light.
2Device complexity
If cholesteric liquid crystal layers are used for diffraction, then compact structure is achieved, but light reflection is reduced and blue shift occurs
Solution Approach 1:
The patent applies parameter changes by carefully controlling the helical pitch of the cholesteric liquid crystal layer to be within a specific range (0.2-2.0 times the wavelength of incident light). This parameter optimization ensures high diffraction efficiency while minimizing blue shift and maintaining strong light reflection, thus resolving the contradiction between compact structure and light reflection efficiency.
3Device complexity
If cholesteric liquid crystal layers are used for diffraction, then compact structure is achieved, but blue shift of reflected light occurs
Solution Approach 1:
The patent applies parameter changes by optimizing the helical pitch parameter of the cholesteric liquid crystal layer. By controlling the pitch to be within a specific range relative to the incident light wavelength, the patent achieves compact structure while suppressing blue shift through proper parameter selection.
Solution Approach 2:
The patent applies dimensionality change by transitioning from conventional 2D surface gratings to 3D volumetric cholesteric liquid crystal structures. This three-dimensional helical arrangement of molecules provides superior optical control, achieving compactness while minimizing blue shift through the volumetric diffraction mechanism.
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 optical element achieves uniform brightness and increased light reflection efficiency, addressing non-uniformity and blue shift issues in augmented reality glasses.
Implementation Method 1
an optical element which 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 a plane
Implementation Method 2
a diffraction element formed of liquid crystal... light incident into a substrate (light guide plate) is diffracted by an optical element
Implementation Method 3
the use of cholesteric liquid crystal layers results in reduced light reflection... ensures uniform brightness and enhanced light reflection
Implementation Method 4
a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in a plane
Data Source
AI summary
Provided are an optical element that can make the brightness of light emitted from a light guide plate uniform, a light guide element, and an image display device. The optical element includes a patterned cholesteric liquid crystal layer that is obtained by immobilizing a cholesteric liquid crystalline phase, in which the patterned 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, and the patterned cholesteric liquid crystal layer has regions having different pitches of helical structures in a plane.