Dual Frequency Liquid Crystal Optical Filter for Scattering-Free Wavelength Tuning
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Solution Overview
Problem
Current wavelength tunable optical filters, particularly those using cholesteric liquid crystals, are limited in their ability to switch between states within a narrow spectral range and often exhibit undesired scattering due to intermediate focal conic structures, which affects their performance in applications requiring broad spectral control, such as UV and blue light management for eye protection and micro-spectrometry.
Innovation Solution
A dual frequency liquid crystal optical filter with a cholesteric liquid crystal mixture and a dual frequency liquid crystal host material, featuring a cross-over frequency below 10 kHz and a threshold voltage under 100 V, allows for electrically controlled wavelength tuning by modulating the applied voltage within specific frequency ranges, avoiding intermediate scattering states and enabling tunability across a broader spectral range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cholesteric liquid crystal devices are used for wavelength tuning, then the filter can be tuned to reflect specific wavelengths, but the device exhibits intermediate scattering states during switching that degrade optical performance
Solution Approach 1:
The patent changes the operating frequency parameter of the liquid crystal device from conventional high frequencies (MHz) to low frequencies (1-100 Hz). This parameter change allows the liquid crystal to switch between planar and homeotropic states without passing through intermediate focal conic states, eliminating scattering and improving optical performance stability while maintaining wavelength tuning capability
Solution Approach 2:
The patent applies periodic voltage switching at low frequencies to control the liquid crystal state transitions. By using periodic action at frequencies of 1-100 Hz, the system can reliably switch between reflection and transmission states without generating intermediate scattering states, thus resolving the contradiction between adaptability and reliability
2Object-affected harmful factors
If passive optical filters are used to block UV and blue light, then eye protection is provided, but color perception and circadian rhythm synchronization are adversely affected
Solution Approach 1:
The patent implements a dynamic optical filter using liquid crystal technology that can actively adjust its spectral transmission characteristics. By applying voltage, the filter dynamically switches between blocking and transmitting specific wavelengths, allowing users to control UV/blue light protection while maintaining natural color perception when protection is not needed
Solution Approach 2:
The patent changes the optical parameters of the filter material from static (passive) to dynamic (electrically controllable). This allows the filter to selectively block harmful UV and blue light wavelengths while transmitting other wavelengths that contribute to color perception, resolving the contradiction between protection and perception quality
3Measurement precision
If multiple fixed wavelength filters are used for different spectral ranges, then specific detection requirements are met, but device complexity and the number of components increase
Solution Approach 1:
The patent implements a universal tunable filter based on liquid crystal technology that can detect multiple wavelengths by changing the applied voltage or frequency. This single device replaces multiple fixed-wavelength filters, maintaining spectral detection accuracy across different wavelengths while significantly reducing device complexity and component count
Solution Approach 2:
The patent uses dynamic control of liquid crystal properties through voltage or frequency modulation to enable a single filter to perform the function of multiple fixed filters. By dynamically adjusting the liquid crystal state, the filter can selectively transmit or reflect different wavelengths, achieving multi-wavelength detection with one component
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 provides a stable and efficient wavelength tunable band-stop filter with reduced scattering, allowing for precise control of Bragg reflection wavelengths from UV to visible ranges, enhancing both eye protection and micro-spectrometry applications by eliminating intermediate scattering states and expanding the tunable spectral range.
Implementation Method 1
the liquid crystal cell having a reference Bragg reflection mode with a planar structure and a reference Bragg reflection wavelength in the spectral range between 300 nm and 900 nm
Implementation Method 2
the liquid crystal cell being configured to apply a voltage (V) between the two electrodes... when the applied voltage is modulated at a frequency higher than a high frequency limit, and wherein the liquid crystal cell has a first Bragg reflection mode with an unwound planar structure
Implementation Method 3
cholesteric liquid crystals (CLC) comprise a liquid crystal host and a chiral dopant resulting in a CLC planar structure defined by a helix pitch and axis
Data Source
Figure 1A~2
Figure 3A~4E
Figure 5
AI summary
The invention concerns a wavelength tunable optical filter and a method for switching and adjusting the wavelength tunable optical filter. According to the invention, the optical filter comprises a liquid crystal cell (1) comprising a cholesteric liquid crystal mixture (2) inserted between two electrodes (13, 14) configured to apply a voltage (V), the cholesteric liquid crystal mixture (2) comprising a chiral dopant and a dual frequency liquid crystal host material, the liquid crystal cell (1) having a reference Bragg reflection wavelength in the spectral range between 300 nm and 900 nm, and the liquid crystal cell having a first Bragg reflection wavelength, when the applied voltage is modulated at a frequency comprised in an intermediate frequency range which is above a cross-over frequency (fc) and below a high frequency limit (fH), the first Bragg reflection wavelength being different from the reference Bragg reflection wavelength and the cholesteric liquid crystal mixture (2) being non-scattering both in the reference Bragg reflection mode and in the first Bragg reflection mode.