Guest-Host Liquid Crystal Filter with Retarder
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Solution Overview
Problem
Traditional liquid crystal variable transmission filters with high-durability input and output polarizers can only transmit 18%-20% of unpolarized light due to high light absorption, limiting their transmittance to less than 50% and causing significant viewing angle dependence, resulting in non-uniform light intensity perception.
Innovation Solution
A guest-host liquid crystal variable transmission filter design with two guest-host liquid crystal devices oriented 180° apart, combined with a polarization state-changing device like a half-wave optical retarder, which improves viewing angle range but reduces contrast ratio, is compensated by the retarder to maintain high transmittance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional high-durability polarizers are used in liquid crystal variable transmission filters, then reliability is improved, but light transmittance deteriorates (only 18%-20% transmission)
Solution Approach 1:
The patent removes the traditional high-durability polarizers from the system entirely, replacing them with a polarizer-free liquid crystal variable transmission filter design that uses liquid crystal molecules oriented at 45° and 135° relative to the horizontal to generate linear polarization states without external polarizing elements
Solution Approach 2:
The patent introduces a half-wave optical retarder as an intermediary component between the first and second guest-host liquid crystal devices to rotate the polarization state of transmitted light by 90°, enabling the system to achieve high transmittance while maintaining polarization control functionality
2Illumination intensity
If polarizer-free design is used to achieve high transmittance, then light transmittance is improved (at least 50%), but viewing angle dependence worsens (non-uniform light intensity perception)
Solution Approach 1:
The patent employs a reverse arrangement where the second guest-host liquid crystal device is rotated 180° about its normal axis with respect to the first device, creating an asymmetric configuration that improves viewing angle characteristics while maintaining high transmittance
Solution Approach 2:
The half-wave optical retarder serves as a compensating intermediary that corrects the viewing angle dependence introduced by the polarizer-free design, rotating polarization states to ensure uniform light intensity perception across different viewing angles
3Ease of operation
If reverse arrangement of liquid crystal directors is used, then viewing angle range is improved, but contrast ratio deteriorates (contrast ratio always less than 2 without compensation)
Solution Approach 1:
The half-wave optical retarder acts as a compensating intermediary positioned between the two guest-host liquid crystal devices, rotating the polarization state of light to restore contrast ratio while preserving the wide viewing angle characteristics provided by the reverse arrangement
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 achieves at least 50% transmission of unpolarized light with minimal color shift and luminance variation over a wide range of incident polar angles, enhancing the filter's performance in applications like smart eyewear with electronic dimming control.
Implementation Method 1
The liquid crystal material has liquid crystal directors with projections lying on the interior surfaces of the first electrode structures
Implementation Method 2
A polarization state-changing device, such as a half-wave optical retarder, is positioned between the first and second guest-host liquid crystal devices
Implementation Method 3
transmittance of light in the first polarization state and in the second polarization state incident on the first guest-host liquid crystal device responds to, respectively, an electric field applied to the first guest-host liquid crystal device and an electric field applied to the second guest-host liquid crystal device
Data Source
Figure 1
Figure 2~3
Figure 4A~4C
AI summary
A variable transmission filter (10) combines in optical series first and second guest-host liquid crystal devices (12, 14) arranged such that one of them is rotated 180° about its normal axis with respect to the other one. The reverse arrangement of the liquid crystal directors of the first and second guest-host liquid crystal devices improves the viewing angle range of the variable transmission filter but, without compensation, introduces a diminution of contrast ratio. A polarization state-changing device (44) positioned between the first and second guest-host liquid crystal devices changes the polarization states of light exiting the first guest-host liquid crystal device such that transmittance of light in first and second orthogonal polarization states incident on the first guest-host liquid crystal device responds to electric fields applied to the first and second liquid crystal devices and thereby counteracts the diminution of contrast ratio while maintaining the improved viewing angle range.