Liquid Crystal Diffraction Element Curved Surface Chromatic Aberration
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Solution Overview
Problem
Liquid crystal diffraction elements face issues with increased chromatic aberration and decreased diffraction efficiency as the diffraction angle increases, particularly due to varying diffraction angles for different wavelengths, leading to reduced performance in optical devices like head-mounted displays.
Innovation Solution
A liquid crystal diffraction element with an optically anisotropic layer featuring a curved surface and a liquid crystal alignment pattern where the optical axis direction continuously rotates in-plane, combining diffraction and refraction effects to minimize chromatic aberration and enhance diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the diffraction angle is increased to improve light direction control, then the diffraction efficiency decreases and chromatic aberration increases
Solution Approach 1:
The patent combines diffraction and refraction effects in a single liquid crystal diffraction element. The optically anisotropic layer is configured to produce both diffraction and refraction simultaneously, where the refraction effect compensates for the wavelength-dependent diffraction angle variations, thereby reducing chromatic aberration while maintaining high diffraction efficiency even at large diffraction angles
Solution Approach 2:
The patent changes the optical parameters of the liquid crystal composition by selecting compounds with specific refractive index anisotropy values (Δn ≥ 0.2). By controlling the refractive index difference between the extraordinary and ordinary rays, the element achieves optimized diffraction efficiency and reduced chromatic aberration across different wavelengths
2Ease of operation
If the diffraction angle is increased to improve light direction control, then chromatic aberration increases due to varying diffraction angles for different wavelengths
Solution Approach 1:
The patent merges diffraction and refraction mechanisms in one element. The refraction component provides a wavelength-independent angular deviation that compensates for the wavelength-dependent diffraction angles, thereby correcting chromatic aberration while maintaining large diffraction angles for improved light direction control
Solution Approach 2:
The patent optimizes the refractive index anisotropy parameter (Δn) of the liquid crystal composition to a value of 0.2 or greater. This parameter change ensures that the refraction effect is sufficiently strong to compensate for chromatic dispersion in diffraction, reducing chromatic aberration across the visible spectrum
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 reduces chromatic aberration and increases diffraction efficiency by aligning the diffraction and refraction angles for different wavelengths, improving the performance of liquid crystal diffraction elements in optical devices.
Implementation Method 1
a liquid crystal diffraction element including an optically anisotropic layer that is formed of a liquid crystal composition containing a liquid crystal compound
Implementation Method 2
the optically anisotropic layer has at least a curved surface portion
Data Source
AI summary
There is provided a liquid crystal diffraction element in which chromatic aberration is small and diffraction efficiency is high in the liquid crystal diffraction element, and an image display apparatus and a head mounted display which use this diffraction element. The liquid crystal diffraction element includes an optically anisotropic layer that is formed of a liquid crystal composition containing a liquid crystal compound, where the optically anisotropic layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating along at least one in-plane direction, and the optically anisotropic layer has at least a curved surface portion.