Achromatic Phase Modulator Using Liquid Crystal Groups
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Solution Overview
Problem
Existing phase modulators using liquid crystal elements cannot achieve uniform phase modulation across a wide wavelength range, such as the visible light spectrum, due to changes in phase modulation quantity with wavelength, limiting their ability to modulate color images from white light sources.
Innovation Solution
An achromatic phase modulator is designed with multiple liquid crystal element groups, each with specific refractive index wavelength dependence characteristics and alignment conditions, allowing for controlled phase modulation across a wide wavelength range by adjusting the alignment directions and applied electric signals to achieve consistent phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single liquid crystal element is used for phase modulation, then the device structure is simple, but the phase modulation quantity changes with wavelength and cannot achieve uniform modulation across a wide wavelength range
Solution Approach 1:
The patent divides the liquid crystal phase modulation system into multiple elements with different refractive index wavelength dependence characteristics. Specifically, it uses at least two liquid crystal elements whose refractive indices change differently with wavelength, allowing their combined phase modulation effects to compensate for wavelength variations and achieve achromatic phase modulation across a broad spectrum.
2Manufacturing precision
If multiple liquid crystal elements with different refractive index characteristics are used, then uniform phase modulation across wide wavelength range is achieved, but the device complexity increases
Solution Approach 1:
The patent changes the parameters of the liquid crystal elements, specifically selecting elements with different refractive index wavelength dependence characteristics. By carefully choosing liquid crystal materials with distinct optical properties and adjusting their thicknesses, the system achieves wavelength-independent phase modulation while managing the complexity through parameter optimization rather than arbitrary multiplication of components.
3Ease of operation
If liquid crystal elements are used for phase modulation, then the phase can be controlled electrically, but the modulation quantity varies with wavelength limiting color image modulation capability
Solution Approach 1:
The patent employs a composite approach by combining multiple liquid crystal materials with different refractive index characteristics into a single phase modulation system. This composite liquid crystal configuration maintains electrical controllability while achieving wavelength-independent phase modulation, thereby enabling the system to handle broadband light sources and modulate color images effectively.
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 achromatic phase modulator achieves uniform phase modulation for light across a wide wavelength range, including non-polarized light, by optimizing the refractive index changes in liquid crystal elements, enabling effective modulation of color images without polarization dependence.
Implementation Method 1
a first liquid crystal element group composed of a pair of liquid crystal elements both of which liquid crystal materials have a first refractive index wavelength dependence characteristics and a second liquid crystal element group composed of a pair of liquid crystal elements both of which liquid crystal materials have a second refractive index wavelength dependence characteristics
Implementation Method 2
The phase modulator disclosed in patent literature 1 modulates a phase of an incident light after converting from non-polarized light to linearly polarized light
Implementation Method 3
a control unit for applying drive electric signals to the liquid crystal elements so as to achieve achromatic phase modulation for the incident light
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(d)
AI summary
An achromatic phase modulator (100) adapted to modulate the phase of an incident beam of light (INCIDENT LIGHT) and to output the thus modulated light, the phase modulator (100) comprising a plurality of liquid crystal elements disposed in series on a light path of the incident light and a control unit (15) comprising a plurality of power sources (14) for applying drive electric signals to the liquid crystal elements, wherein the plurality of liquid crystal elements comprises at least a first and a second liquid crystal element groups (FIRST LIQUID CRYSTAL ELEMENT GROUP; SECOND LIQUID CRYSTAL ELEMENT GROUP), each group being composed of a pair of liquid crystal elements, the liquid crystal elements of the first and second group respectively being made of a first and a second liquid crystal material having a first and and a second, different, refractive index wavelength dependence characteristic, the thicknesses (dl/2, d2/2) of the liquid crystal elements forming each group being equal.