A Light Transmission Based Liquid Crystal Thermography System

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Timothy B. Roth ◽  
Ann M. Anderson
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Light Transmission ◽  
Intensity Variation ◽  
Ccd Camera ◽  
Light Reflection ◽  
Transmission Characteristics ◽  
Lighting Conditions ◽  
Thermochromic Liquid Crystals

This paper presents results from a study aimed at developing a novel thermochromic liquid crystal (TLC) temperature measurement system that uses light transmission instead of light reflection to measure surface temperature fields. In previous work, we reported on the effect of temperature on light transmission through TLCs as measured with a spectrophotometer [Roth, T. B., and Anderson, A. M., 2005, “Light Transmission Characteristics of Thermochromic Liquid Crystals,” Proceedings of IMECE2005, Orlando, FL, Paper No. IMECE2005-81812;Roth, T. B., and Anderson, A. M., 2007, “The Effects of Film Thickness, Light Polarization and Light Intensity on the Light Transmission Characteristics of Thermochromic Liquid Crystals,” ASME J. Heat Transfer, 129(3), pp. 372–378]. Here we report on results obtained using a charge coupled device (CCD) camera and polychromatic light setup that is similar to the type of equipment used in TLC reflection thermography. We tested three different light sources, a white electroluminescent light, a green electroluminescent light, and a halogen fiber optic light, using both direct and remote lighting techniques. We found that the green signal (as detected by the CCD camera) of the green electroluminescent light makes the best temperature sensor, because under remote lighting conditions it showed a 500% linear signal increase as the temperature of the R25C10W TLCs was raised from 30°to48°C. We further found that the angle of the CCD camera relative to the light did not significantly affect the results for angles up to 10deg for remote lighting and 15deg for direct lighting. The effect of light intensity variation was not significant for intensities up to 40% of the original level when normalized on the intensity at 19°C (a temperature outside the active range of the TLCs). The use of light transmission results in a larger range of temperature over which the TLCs can be calibrated and offers opportunities for more uniform lighting conditions, which may help overcome some of the problems associated with light reflection.

The Effects of Film Thickness, Light Polarization, and Light Intensity on the Light Transmission Characteristics of Thermochromic Liquid Crystals

2006 ◽  
Vol 129 (3) ◽  
pp. 372-378 ◽  
Author(s):  
Timothy B. Roth ◽  
Ann M. Anderson
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Temperature Measurement ◽  
Light Transmission ◽  
Transmission Spectra ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Thermochromic Liquid Crystal ◽  
Thermochromic Liquid Crystals

Thermochromic liquid crystal materials change their crystalline structure and optical properties with temperature, making them useful in temperature measurement applications. This paper presents the results of a study to develop a temperature measurement system that uses light transmission through thermochromic liquid crystals instead of light reflection. We painted Hallcrest R25C10W sprayable liquid crystals on a clear surface and placed it in a spectrophotometer. The amount of light transmitted at monochromatic wavelengths from 400nm to 700nm was measured for temperatures from 25°C to 55°C under conditions of nonpolarized, linearly polarized, and cross-polarized light, for three light intensity levels, and three liquid crystal layer thicknesses. As the temperature was increased the amount of light transmitted through the liquid crystal layer increased. When the liquid crystals are in their active range the transmission spectra exhibit an s-curve shape and the percent of light transmitted through the liquid crystals at a fixed temperature increases with increasing wavelength. We detected significant changes in the transmission spectra for temperatures from 27°C to 48°C, whereas when used with reflected light the thermochromic liquid crystals are useful over a significantly smaller range. As the thickness of the thermochromic liquid crystal layer increases or as the incoming light intensity decreases, the amount of light transmitted through the liquid crystals decreases. We also investigated the effects of temperature overheat on the transmission spectra and found that heating the thermochromic liquid crystals above their active range increases the amount of light transmission. However, when the liquid crystals are cooled below their active range they return to their original state. We have analyzed the spectrophotometer data in a number of ways including: (a) total amount of light transmitted, (b) amount of red, green, and blue light transmitted; and (c) spectral curve shape characteristics (peak transmission, inflection wavelength and wavelength for peak transmission) all as a function of temperature. A linear relationship exists between temperature and all of these variables which we believe can be exploited for the development of a charge coupled light camera based light transmission system for temperature measurement.

scholarly journals Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 908
Author(s):  
Fabrizio Ciciulla ◽  
Annamaria Zaltron ◽  
Riccardo Zamboni ◽  
Cinzia Sada ◽  
Francesco Simoni ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Lithium Niobate ◽  
Photovoltaic Effect ◽  
Optical Control ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Threshold Behaviour ◽  
All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

scholarly journals Holographic Characteristics of Photopolymers Containing Different Mixtures of Nematic Liquid Crystals

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 325 ◽  
Author(s):  
Sandra Fenoll ◽  
Francisco Brocal ◽  
José David Segura ◽  
Manuel Ortuño ◽  
Augusto Beléndez ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Electric Field ◽  
Diffraction Efficiency ◽  
Applied Voltage ◽  
Nematic Liquid Crystals ◽  
Variable Electric Field ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed

A holographic polymer dispersed liquid crystal (HPDLC) is used to record holographic diffraction gratings. Several mixtures of nematic liquid crystals (LC) are used as components of the HPDLC to evaluate their influence in static and dynamic basic properties. The diffraction efficiency obtained in the reconstruction of the holograms is evaluated to compare the influence of the different LC. Additionally, the samples are exposed to a variable electric field and the diffracted light intensity as a function of the applied voltage is measured to evaluate the influence of the LC. The results obtained show significant differences depending on the LC incorporated to the photopolymer.

scholarly journals Effects of Cage Position and Light Transmission on Home Cage Activity and Circadian Entrainment in Mice

2022 ◽  
Vol 15 ◽  
Author(s):  
Laura C. E. Steel ◽  
Selma Tir ◽  
Shu K. E. Tam ◽  
James N. Bussell ◽  
Manuel Spitschan ◽  
...  
Keyword(s):  
Light Intensity ◽  
Home Cage ◽  
Light Transmission ◽  
Activity Levels ◽  
Circadian Activity ◽  
Light Spectrum ◽  
Lighting Conditions ◽  
Cage Activity ◽  
Room Design ◽  
Home Cage Activity

Light is known to exert powerful effects on behavior and physiology, including upon the amount and distribution of activity across the day/night cycle. Here we use home cage activity monitoring to measure the effect of differences in home cage light spectrum and intensity on key circadian activity parameters in mice. Due to the relative positioning of any individually ventilated cage (IVC) with regard to the animal facility lighting, notable differences in light intensity occur across the IVC rack. Although all mice were found to be entrained, significant differences in the timing of activity onset and differences in activity levels were found between mice housed in standard versus red filtering cages. Furthermore, by calculating the effective irradiance based upon the known mouse photopigments, a significant relationship between light intensity and key circadian parameters are shown. Perhaps unsurprisingly given the important role of the circadian photopigment melanopsin in circadian entrainment, melanopic illuminance is shown to correlate more strongly with key circadian activity parameters than photopic lux. Collectively, our results suggest that differences in light intensity may reflect an uncharacterized source of variation in laboratory rodent research, with potential consequences for reproducibility. Room design and layout vary within and between facilities, and caging design and lighting location relative to cage position can be highly variable. We suggest that cage position should be factored into experimental design, and wherever possible, experimental lighting conditions should be characterized as a way of accounting for this source of variation.

Study of Infrared Imaging System Based on Liquid-Crystal Thermo-Optic Effect

2011 ◽  
Vol 181-182 ◽  
pp. 106-109
Author(s):  
Ya Zhang ◽  
Chang Long Cai ◽  
Xiao Ling Niu ◽  
Wei Guo Liu
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Infrared Imaging ◽  
Imaging System ◽  
Optical Rotation ◽  
Cholesteric Liquid Crystals ◽  
Optical Readout ◽  
The Difference ◽  
Uneven Heating

In this paper, based on the optical rotation property of cholesteric liquid crystals, a new system for studying the optical readout infrared imaging was designed. The profile of hot object is imaged on the surface of liquid crystal cell through the infrared lens, as the uneven heating, the optical rotation is different in various parts of the cholesteric liquid crystals, especially in the imaging area and non-imaging area, the difference is larger. Through the optical system, the optical rotation signal is translated into the corresponding light intensity signal, then the light intensity signal is collected by the visible CCD, and the image of the hot object will be displayed on the screen.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

scholarly journals Liquid Crystal Devices for Beam Steering Applications

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 247
Author(s):  
Rowan Morris ◽  
Cliff Jones ◽  
Mamatha Nagaraj
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Adaptive Optics ◽  
Beam Steering ◽  
Optical Components ◽  
Advantages And Disadvantages ◽  
Liquid Crystal Devices

Liquid crystals are valuable materials for applications in beam steering devices. In this paper, an overview of the use of liquid crystals in the field of adaptive optics specifically for beam steering and lensing devices is presented. The paper introduces the properties of liquid crystals that have made them useful in this field followed by a more detailed discussion of specific liquid crystal devices that act as switchable optical components of refractive and diffractive types. The relative advantages and disadvantages of the different devices and techniques are summarised.

scholarly journals Optical Response Associated with the Orientation and Structure of Liquid Crystals with Respect to Phosphatidylcholine Concentration

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 678
Author(s):  
Yuqi Han ◽  
Yan Jiang ◽  
Wei Guo ◽  
Bing Li ◽  
Lu Zhang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Reflectance Spectrum ◽  
Optical Response ◽  
The Self ◽  
Cholesteric Liquid Crystals ◽  
Anchoring Effect ◽  
Self Assembling ◽  
Sensitization Effect ◽  
Structure Of Liquid

Based on the anchoring effect due to the self-assembling behavior of the phospholipid molecules at the interface between the liquid crystal and water phases on the orientation of liquid crystals, the optical response associated with the orientation and structure of liquid crystals with respect to the concentration of 1,2-didodecanoyl-sn-glycero-3-phosphocholine solution has been investigated. The optical response owing to changes in the orientation and structure of the mixed cholesteric liquid crystals with respect to the change in the concentration of phosphatidylcholine has been obtained. Moreover, the feasibility of using as-prepared mixed cholesteric liquid crystals to measure the phosphatidylcholine concentration has been verified. A methodology to measure the reflectance spectrum by using mixed cholesteric liquid crystals to sensitize the phosphatidylcholine concentration has been further realized. The sensitization effect of the mixed cholesteric liquid crystals on the measurement of phosphatidylcholine concentration was also verified.

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