Laminated Liquid Crystal Diffraction Lattice for Birefringence Compensation
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Solution Overview
Problem
Existing optical elements using liquid crystal diffraction lattices suffer from birefringence effects when sensing light with wavelengths different from the diffracted light, leading to changes in light intensity and sensing errors due to oblique passage through the lattice.
Innovation Solution
A laminated optical element comprising a first optically anisotropic layer with a rod-like liquid crystal compound and a second optically anisotropic layer with a disk-like liquid crystal compound, where the optical axes of both layers rotate continuously and rotationally, allowing for controlled in-plane retardation and compensation of birefringence effects across different wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a liquid crystal diffraction lattice is used to diffract visible light, then beam steering function is achieved, but birefringence occurs for infrared light causing polarization state changes and sensing errors
Solution Approach 1:
The patent uses a composite liquid crystal system combining rod-like liquid crystal compounds (for visible light diffraction) and disk-like liquid crystal compounds (for infrared light compensation). This composite structure allows the material to simultaneously provide beam steering for visible light while compensating for birefringence effects on infrared light, resolving the contradiction between functional versatility and harmful birefringence effects.
Solution Approach 2:
The patent changes the molecular shape parameter of the liquid crystal compounds from rod-like to disk-like in the second layer, which fundamentally alters the optical properties. This parameter change enables the second layer to compensate for the birefringence introduced by the first layer, allowing infrared light to pass through without polarization state changes while maintaining visible light diffraction functionality.
2Productivity
If rod-like liquid crystal compound is used for diffraction, then visible light beam steering is achieved, but infrared light experiences retardation and polarization changes
Solution Approach 1:
The patent converts the harmful birefringence effect of the rod-like liquid crystal compound into a beneficial compensation mechanism. By introducing a second layer of disk-like liquid crystal compounds with specific orientation characteristics, the patent makes the harmful retardation effect of the first layer counteract the birefringence, thereby converting a source of error into a correction mechanism that improves sensing accuracy.
Solution Approach 2:
The patent changes the molecular geometry parameter from rod-like to disk-like shape in the second layer, which fundamentally alters the optical interaction with infrared light. This parameter change enables the second layer to provide compensation for the retardation caused by the first layer, maintaining diffraction efficiency while improving sensing reliability.
3Ease of operation
If liquid crystal alignment pattern is changed for beam steering, then reflection direction control is achieved, but wavelength-dependent birefringence causes intensity changes
Solution Approach 1:
The patent employs a composite structure where the first layer of rod-like liquid crystal compounds provides reflection direction control through its alignment pattern, while the second layer of disk-like liquid crystal compounds compensates for wavelength-dependent intensity changes. This composite material approach allows independent optimization of steering functionality and intensity stability.
Solution Approach 2:
The patent changes the optical axis orientation parameter between the two layers, with the first layer having optical axes parallel to the surface for steering control and the second layer having optical axes at specific angles for intensity compensation. This parameter differentiation enables simultaneous achievement of direction control and intensity stability across different wavelengths.
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 effectively diffracts desired light while transmitting light of different wavelengths without birefringence influence, reducing sensing errors and maintaining high diffraction efficiency.
Implementation Method 1
the phase of light reflected by a cholesteric liquid crystal is changed by the phase of a helical structure, and the phase of the helical structure is spatially controlled, and thus the wave surface of the reflected light can be optionally designed
Implementation Method 2
infrared light Llr obliquely passes through the liquid crystal diffraction lattice 1 to cause a retardation, and thus the polymerization direction of the infrared light before being incident on the liquid crystal diffraction lattice 1, for example, the state of linearly polarized light is changed to a different state of polarized light
Implementation Method 3
An element (hereinafter, referred to as a liquid crystal diffraction lattice) that diffracts light by changing the liquid crystal alignment pattern in the plane
Data Source
AI summary
The optical element is an optical element including a first optically anisotropic layer which is a cured layer of a liquid crystal composition containing a rod-like liquid crystal compound and a second optically anisotropic layer which is laminated on the first optically anisotropic layer and is a cured layer of a liquid crystal composition containing a disk-like liquid crystal compound, wherein each of the first optically anisotropic layer and the second optically anisotropic layer, has a liquid crystal alignment pattern in which an optical axis of the rod-like liquid crystal compound and an optical axis of the disk-like liquid crystal compound are respectively parallel to a surface of the optically anisotropic layer and oriented along at least one in-plane direction, orientation of the optical axis changes continuously and rotationally, and the orientation of the optical axis rotates by 180° with a period of 0.5 μm to 5 μm.