Polymeric materials based on polystyrene (PS) are one of the most common polygraph materials. It is necessary to differentiate between of optical homogeneity of the polycrystalline structure of PS. We aim to demonstrate the use of a polarization interference method to allow quick and easy practical differentiation between PS samples with different types of deformations. Polycrystalline optically homogeneous and mechanically stressed samples of PS were investigated. We map the local contrast of interference patterns in microscopic images of образцов PS using a set-up polarizing interferometer, based on the superposition of a reference laser beam with the interference pattern of the sample in the image plane. The local contrast distributions can be directly related to the polycrystalline structure of образцов PS. The dependences of the magnitude of the 1st to 4th order statistical moments of the local contrast polarization-interference distribution are determined. To determine the diagnostic potential of the method две groups of polycrystalline образцов PS were formed. The first group contained 16 optically homogeneous PS samples, while the second contained 16 PS samples with residual mechanical stresses.
At present, liquid crystals – polymer (LC-P) composites such as polymer-dispersed liquid crystals (PDLC), polymer stabilized liquid crystals (PSLC) and polymer networks in liquid crystals (PNLC) are widely used as operating elements of optical devices such as microlens and elements, whose principle of operation is based on light scattering. LC-P composites light refraction features depend on shape and size of liquid crystal (LC) drops as well as on director orientation inside of drops. LC anisotropy influences polarization characteristics of refracted radiation. We have investigated desined as the tunable microlens on LC-P with different components concentration ratio. We have used LC E7 by Merck, dispersed in the polymer NOA 65 by Norland Inc. as the object of research. They have close refractive indeces which provide the posibility to shange the focal length of such LC lens in wide range. We change focal length by change of applied voltage and by rotation of polarization plane of illuminating beam. Partial beams passed through LC droplets and polymer matrix may be considered as plane waves passing different optical pathes and interfering in the far zone. Changing the voltage results in changing the LC effective refractive index leading to a change of the path difference between the interfering beams. The effect of interference decreases of some spectral components of the radiation passing through LC-P sample can be used as a tunable chromatic lens.
The condenser is one of the most important components in many transmitted light compound microscopes. In this Letter, was shown that such a condenser can be replaced by a solution of liquid crystal in a polymer matrix (PDLC) and back light lamp to achieve greater imaging flexibility and functionality. By changing the voltage applying to the PDLC, we change the amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the spatial-frequency filtering by PDLC. Without mechanically scanning the sample or changing the microscope setup, the proposed approach can be used for dark-field imaging, bright-field imaging, microscopy sectioning, and digital refocusing. Images of a starfish embryo were acquired by using such an approach for demonstration.
Experimental investigations of the effects of limiting of a beam traversing a different light-scattering medium based on liquid crystals are presented. It is shown that the result of limiting of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Investigations of the effects of limiting has been carried out using nematic liquid crystals MBBA with carbon nanotubes (CNT) in comparison wihs a solution of the same liquid crystals doped by carbon nanodots. Liquid crystals dopped by carbon nanotubes or nanodots, located between crossed polarizers, delays external optical radiation as its power increases to a certain critical level. This can be explained by the phase changes in the LC dopped by the nanoparticles under the action of heating aimed by radiation or an applying external electromagnetic field. Observed phenomena strongly influenced by shape, size and concentration of CNT, as well as the sensitivity of the liquid crystal to the illuminating beam power rate has increased.
Beam colouring effects traversing a different light-scattering medium based on liquid crystals experimental investigations are presented. It was first time shown that the result of the beam colouring at the medium output depends on the singly forward scattered partial signals phase delays magnitudes. Colouring effects spectral investigation has been carried out using both nematic liquid crystals with carbon nanotubes and the solution of liquid crystal in a polymer matrix which was previously investigated. The non-scattered and the singly forward scattered interfering components amplitude ratio significantly affects the colour intensity in both samples. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation. The colouring effect significant increase has been achieved due to the injection of carbon nanotubes, as well as the sensitivity of the liquid crystal to the control electric field has increased.
Experimental investigations of the effects of colouring of a beam traversing a different light-scattering medium based on liquid crystals are presented. It is shown that the result of colouring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Spectral investigation of the effects of colouring has been carried out using nematic liquid crystals with carbon nanotubes in comparison wihs a solution of liquid crystal in a polymer matrix which was previously investigated. The amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the colour intensity. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation. Due to the injection of carbon nanotubes, a significant increase of colouring effect has been achieved, as rell as the sensitivity of the liquid crystal to the control electric field has increased.
Experimental investigations of the effects of colouring of a beam traversing a light-scattering medium is presented. It is shown that the result of colouring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Spectral investigation of the effects of colouring has been carried out using a solution of liquid crystal in a polymer matrix. The amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the colour intensity. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation.
This research is aimed to develop a new method of polymer dispersed liquid crystal morphology estimation. The possibility of application of the Mueller matrix approach for separate observation of isotropic and anisotropic parts of different PDLC samples was illustrated in it.
We analyze the effects of coloring of a beam traversing a light-scattering medium. Spectral investigation of the effects of coloring has been carried out using a solution of liquid crystal in a polymer matrix (PDLC). It is shown that the result of coloring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. We consider the influence of interference coloring effect on the transmission scattering and spatial-frequency filtering of the radiation which has passed through the PDLC.
The methods of correlation optics are for the first time applied to study structure of liquid crystal (LC) – polymer (P) composites at various concentrations of LC and P. Their phase correlation function (PCF) was obtained considering LC-P composite as a random phase screen. The amplitude of PCF contains information about number of LC domains and structure of LC director inside of them, while a half-width of this function is connected with a size of these domains. We studied unpowered and powered composite layers with a thickness of 5 μm. As liquid crystal and polymer were used nematic LC E7 from Merck and photopolymer composition NOA65 from Norland. Concentration of polymer φP was varied in a range 10-55 vol. %. In good agreement with previous studies by SEM technique we detected monotone decrease of LC domains with concentration of polymer. With application of electric field, amplitude of PCF behaves differently for the samples with different polymer content. For the samples with φP>35 vol. % (samples having morphology of polymer dispersed LC), this dependence is monotonic. In turn, if φP<35 vol. % (samples with polymer network LC morphology), the amplitude of PCF non-monotonically depends on the applied voltage going through a maximum. The latter fact is explained by transformation of orientational defects of LC phase with the applied voltage.
We analyze the effects of coloring of a beam traversing a light-scattering medium. Spectral investigation of the effects of coloring has been carried out using a solution of liquid crystal in a polymer matrix (PDLC). It is shown that the result of coloring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. We consider the influence of interference coloring effect on the transmission scattering and spatial-frequency filtering of the radiation which has passed through the PDLC.
The methods of correlation optics are for the first time applied to study structure of liquid crystal (LC) – polymer (P) composites at various concentrations of LC and P. Their phase correlation function (PCF) was obtained considering LC-P composite as a random phase screen. The amplitude of PCF contains information about number of LC domains and structure of LC director inside of them, while a half-width of this function is connected with a size of these domains. We studied unpowered and powered composite layers with a thickness of 5 μm. As liquid crystal and polymer were used nematic LC E7 from Merck and photopolymer composition NOA65 from Norland. Concentration of polymer ϕP was varied in a range 10-55 vol. %. In good agreement with previous studies by SEM technique we detected monotone decrease of LC domains with concentration of polymer. With application of electric field, amplitude of PCF behaves differently for the samples with different polymer content. For the samples with ϕP<35 vol. % (samples having morphology of polymer dispersed LC), this dependence is monotonic. In turn, if ϕP<35 vol. % (samples with polymer network LC morphology), the amplitude of PCF non-monotonically depends on the applied voltage going through a maximum. The latter fact is explained by transformation of orientational defects of LC phase with the applied voltage.
Experimental investigations of the effects of colouring of a beam traversing a light-scattering medium is presented. It is shown that the result of colouring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Spectral investigation of the effects of colouring has been carried out using a solution of liquid crystal in a polymer matrix. The amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the colour intensity. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation.
We investigate scattering indicatrix and Mueller matrix elements of scattered radiation for different voltages applying to
the polymer dispersed liquid crystals cell. We observe modulation of scattering indicatrix and Mueller matrix elements
with period equals to 2.5°. We calculate the size of LC drops in polymer matrix that equals to 7.25 μm which is confirmed
by microscopic research. We construct spatial frequency filter for separation of large and small details of images.
This research is aimed to develop a new method of polymer dispersed liquid crystal morphology estimation. The possibility of
application of the Mueller matrix approach for separate observation of isotropic and anisotropic parts of different PDLC
samples was illustrated in it.
At present time a liquid crystals using in engineering are based on their optical properties such as strong anisotropy,
specific equilibrium of molecular skeleton, sensitivity to external action, appearance of compound and involute structure
which selectively respond to the light with adjusted frequency and polarization, etc. This behaviour make them are
perspective environment for application in optical devices like mesomorphic active components (electrooptic shutters,
spherical and cylindrical lenses, optical filters, light-induced time and space grids, nonlinear mirrors).
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