Cholesteric Liquid Crystal Light Guide for AR Color Shift
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Solution Overview
Problem
Augmented reality (AR) glasses face the challenge of color shift due to wavelength-dependent light diffraction, requiring multiple light guide plates for each color, resulting in a thick, heavy device with complex configuration.
Innovation Solution
A light guide element comprising a plurality of cholesteric liquid crystal layers with different selective reflection center wavelengths, where the length of the single period in the liquid crystal alignment pattern matches the permutation of selective reflection center wavelengths, allowing red, green, and blue light to be reflected in the same direction, eliminating the need for multiple light guide plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple light guide plates are used for each color (red, green, blue) to eliminate color shift, then color accuracy is improved, but device thickness and weight increase
Solution Approach 1:
The patent combines multiple light guide plates for different colors (red, green, blue) into a single integrated light guide plate. This is achieved by providing a diffraction element with different diffraction angles for different wavelengths within the same plate, allowing all color components to be guided simultaneously without spatial separation, thereby eliminating color shift while reducing device thickness.
Solution Approach 2:
The patent changes the diffraction angle parameter of the diffraction element based on wavelength. By designing the diffraction element to have wavelength-dependent diffraction angles, light components of different wavelengths are diffracted at different angles to converge at the same exit position, achieving color-accurate guidance in a single plate without requiring multiple separate plates.
2Manufacturing precision
If multiple light guide plates are used for each color (red, green, blue) to eliminate color shift, then color accuracy is improved, but device weight increases
Solution Approach 1:
The patent merges multiple separate light guide plates (one for each color) into a single multi-functional light guide plate. This integration reduces the total material used and eliminates the need for multiple discrete components, thereby reducing overall device weight while maintaining color accuracy through wavelength-specific diffraction angles.
Solution Approach 2:
The single light guide plate performs multiple functions by guiding different color components (red, green, blue) simultaneously with appropriate diffraction angles. This multi-functional design replaces what would traditionally require three separate specialized plates, achieving weight reduction while maintaining the ability to accurately guide each color component.
3Device complexity
If a single light guide plate is used with wavelength-dependent diffraction, then device complexity is reduced, but color shift occurs
Solution Approach 1:
The patent applies parameter changes to the diffraction angle based on wavelength within the single light guide plate. By designing the diffraction element to provide different diffraction angles for different wavelengths (red, green, blue), the system maintains color accuracy without requiring multiple separate plates, thus reducing device complexity while preventing color shift.
4Productivity
If diffraction element is used to introduce light at specific angles, then light guidance efficiency is improved, but color shift occurs due to wavelength dependence
Solution Approach 1:
The patent utilizes wavelength-dependent diffraction angle parameters to achieve both efficient light guidance and color accuracy. The diffraction element is designed so that each wavelength component (red, green, blue) is diffracted at a specific angle appropriate for its wavelength, ensuring efficient coupling into the light guide plate while all components converge at the correct exit position, thereby maintaining both efficiency and color accuracy.
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 reduces the wavelength dependence of the reflection angle, enabling a single light guide plate to guide light components without color shift, resulting in a thinner, lighter AR glasses with improved viewing angles.
Implementation Method 1
a plurality of cholesteric liquid crystal layers having different selective reflection center wavelengths
Implementation Method 2
an optical element comprising a plurality of cholesteric liquid crystal layers that are laminated, the cholesteric liquid crystal layers being obtained by immobilizing a cholesteric liquid crystalline phase
Data Source
AI summary
An object is to provide an optical element in which a wavelength dependence of reflection is small, a light guide element including the optical element, and an image display device including the light guide element. The optical element includes a plurality of cholesteric liquid crystal layers having different selective reflection center wavelengths, 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, and in a case where a length over which the optical axis rotates by 180° in the in-plane direction is set as a single period, a permutation of lengths of selective reflection center wavelengths and a permutation of lengths of the single periods match each other in the cholesteric liquid crystal layers.