Liquid crystal polarization interference element, optical filter, and optical system
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Solution Overview
Problem
Existing band-pass filters experience a wavelength shift when light is incident from an oblique direction, leading to fluctuations in maximum transmittance.
Innovation Solution
A liquid crystal polarization interference element is designed with alternating layers of horizontally and vertically aligned rod-like and disk-like liquid crystal compounds, where the in-plane slow axes of each layer are parallel or intersect, and the in-plane retardations are equal, to stabilize the wavelength of maximum transmittance across different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional band-pass filter is used, then light transmission in a specific wavelength range is achieved, but wavelength shift occurs when light is incident from an oblique direction
Solution Approach 1:
The patent employs a composite structure combining liquid crystal layers with rod-like and disk-like compounds in alternating arrangements. This composite material approach allows the combination of different liquid crystal phases to compensate for each other's optical anomalies, thereby suppressing wavelength shift while maintaining stable band-pass filtering characteristics across oblique incidence angles.
Solution Approach 2:
The patent introduces local quality variations by alternating between rod-like and disk-like liquid crystal layers with different orientations and retardation characteristics. Each layer has specific local optical properties (slow axis directions, retardation values) that are optimized to compensate for wavelength dispersion, creating overall wavelength-stable performance through spatial distribution of different material properties.
2Reliability
If liquid crystal layers with different orientations are used, then wavelength shift is suppressed, but device structure becomes more complex
Solution Approach 1:
The patent segments the liquid crystal polarization interference element into multiple alternating layers of rod-like and disk-like liquid crystal compounds. Each segment (layer) has a specific orientation and retardation characteristic, and the alternating arrangement allows independent optimization of each segment while achieving overall wavelength stability. This segmentation makes the complex structure more manageable and manufacturable.
Solution Approach 2:
The patent employs a periodic alternating structure of rod-like and disk-like liquid crystal layers with regular intervals. This periodic arrangement creates a repeating pattern of optical compensation that systematically cancels wavelength shift effects. The periodicity also simplifies the manufacturing process and allows for standardized fabrication techniques.
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 effectively suppresses wavelength shifts, ensuring consistent maximum transmittance regardless of light incidence direction, by offsetting thickness-direction retardations through equal in-plane retardations and aligned slow axes.
Implementation Method 1
a liquid crystal polarization interference element including: two or more liquid crystal layer sets in a thickness direction, each set consisting of a first liquid crystal layer and a second liquid crystal layer... an in-plane slow axis of the liquid crystal layer R1 and an in-plane slow axis of the liquid crystal layer D1 are parallel to each other... a sum of in-plane retardations of the liquid crystal layers R1 and a sum of in-plane retardations of the liquid crystal layers D1 are equal to each other
Implementation Method 2
the first liquid crystal layer includes at least one liquid crystal layer R1 formed by immobilizing horizontally aligned rod-like liquid crystal compounds, and at least one liquid crystal layer D1 formed by immobilizing vertically aligned disk-like liquid crystal compounds
Data Source
AI summary
A liquid crystal polarization interference element is provided that suppresses fluctuation in the wavelength at which maximum transmittance occurs, even when light is incident at an oblique angle. The element includes two or more sets of liquid crystal layers, each set having a first liquid crystal layer and a second liquid crystal layer. Each of the first and second liquid crystal layers includes a liquid crystal layer R formed by immobilizing horizontally aligned rod-like liquid crystal compounds and a liquid crystal layer D formed by immobilizing vertically aligned disk-like liquid crystal compounds. The liquid crystal layer R and the liquid crystal layer D have parallel slow axes and equal in-plane retardations, and the first liquid crystal layer and the second liquid crystal layer have in-plane slow axes that intersect each other. An optical filter including the liquid crystal polarization interference element is also provided.