Multiple-beam Fizeau Fringes In Transmission Research Articles

Opto-thermal properties of fibres: 3-effect of anisotropic optical parameters in polypropylene fibres as a function of annealing process

This study deals with the changes in the optical properties of polypropylene fibres (4:1 draw ratio 515 tex polypropylene, Bolton, UK) due to the effect of thermal annealing on its structural characteristics. Changes in the structure of annealed polypropylene fibres at a constant time of 2 h and different temperatures (60–140 °C) were studied interferometrically. The diffraction of a He-Ne laser beam was used to measure the dimensional parameters transverse sectional shape and the area of the polypropylene fibres sections. An optical microscope was used to confirm the geometrical parameters of the cross-sections. The diffraction technique was utilized to study the effect of annealing on swelling factors of these fibres for some different liquids at room temperature 19 ± 1 °C. Two methods were applied for the measurement of the refractive indices and birefringence of the polypropylene annealed and unannealed fibres. The first was concerned with the application of the Becke-line method for determining the refractive indices and the birefringence of the skin layer. The second method used multiple-beam Fizeau fringes in transmission to observe the changes in the values of the refractive indices due to the annealing process in the skin and core layers. Also, the mean refractive indices and their profiles were determined, taking the refraction and different temperatures into consideration. The resulting data were used to calculate the polarizabilities per unit volume and the isotropic refractive index.

Dynamic optomechanical behaviour investigations on undrawn polypropylene fibres

A stress-strain device is constructed and connected to a wedge interferometer. It is used to investigate interferometrically the dynamic optomechanical properties of a polymer fibre. Multiple-beam Fizeau fringes in transmission using this equipment are used for carrying out the investigation on undrawn polypropylene fibres. The mean refractive indices and birefringence are calculated at different stresses and draw ratios. An empirical formula is deduced for the relation between the stress and the mean birefringence for undrawn polypropylene fibres and the constants of this formula are determined. The stress-strain diagram of this fibre is studied also. Poisson's ratio, Young's modulus, elastic shear modulus, yield stress and yield strain are calculated. Also an expression is proposed which is valid for either Young's modulus or elastic shear modulus related to the birefringence and the constants in this expression are determined for each case. The effect of stress on the refractive index profile is investigated. Microinterferograms are given for illustration.

Effect of the oxidative power of iodination on the optical properties of Alpaca fibres

This study deals with the changes in the optical properties of Alpaca fibres due to the effect of the oxidative power of iodine on the structural characteristics of Alpaca fibres. The diffraction of a He-Ne laser beam was used to measure the dimensional parameters, transverse sectional shape and area of the Alpaca fibre sections. Optical and scanning electron microscopes were used to confirm the geometrical parameters of the cross-sections. Two methods were applied for the measurement of the refractive indices and birefringence of the Alpaca wool fibres. The first was concerned with the application of multiple-beam Fizeau fringes in transmission before treating the fibre with iodine. The second method made use of a double refracting interference microscope (the Pluta polarizing interference microscope). The double beam technique was considered the most suitable in determining the mean refractive indices and the double refraction of the samples after the iodine treatment. Large changes were observed in the values of the refractive indices due to the iodination process, while the birefringence exhibited no appreciable change. Examination of the Alpaca fibres by X-ray diffractometry showed that the crystalline parts had been completely decomposed and degraded due to the effect of I 2, which causes oxidative scission of the intermolecular disulphide bonds of the keratins.

Interferometric studies on fibres with irregular transverse sections

Multiple-beam Fizeau fringes in transmission and at reflection were applied to the study of the optical properties of fibres with irregular cross-section ( Orlon 42 and nylon fibres). The mathematical expressions used for the application of multiple-beam Fizeau fringes to determine the refractive indices and birefringence of fibres are given. The experimental techniques used for producing multiple-beam Fizeau fringes in transmission and at reflection are also given. Interferometric methods were applied to study the variation of refractive indices with wavelength of light and along the fibre axis. Values of refractive indices were used to calculate Cauchy's dispersion constants. The value of thermal coefficient of refractive index has been calculated. Illustrations are given using multiple-beam interferograms.

Opto-mechanical properties of fibres—5: Refractive index profile of stretched ‘terylene’ polyester fibres

The changes of cross-sectional area and refractive-index profile of ‘Terylene’ polyester fibres after stretching have been studied. The cross-sectional shape is determined from the diffraction pattern of a HeNe laser beam. Multiple-beam Fizeau fringes in transmission are used to determine the refractive index profile of these fibres at different draw ratios. A microstrain device connected to a wedge interferometer is utilized for this purpose. Microinterferograms are given for illustration.

Opto-mechanical properties of fibres. 3: Optical properties of Nylon 66 fibres as a function of the draw ratio

Refractive indices and birefringence of six samples of nylon 66 fibres having different draw ratios are determined using two-beam and multiple-beam microinterferometry. Four independent techniques have been used for this purpose. The first one used a HeNe laser beam to determine the geometrical parameter of the fibre from its diffraction pattern. The second is the application of the Becke-line method to determine refractive indices and birefringence of the fibre's skin. The third is the application of multiple-beam Fizeau fringes in transmission to determine the mean refractive indices and mean birefringence of these fibres with different draw ratios. Finally, the Pluta polarising interference microscope have been used for determining the mean refractive indices and mean birefringence of these fibres. Relationships between the mean refractive indices, birefringence and polarisabilities per unit volume with draw ratio are given for these fibres. Illustrations are given using microinterferograms.

Opto-mechanical properties of fibres—1: Optical Anisotropy in stretched nylon 6 fibres

Multiple-beam Fizeau fringes in transmission have been used to study the changes of refractive indices and birefringence of nylon 6 fibres extended dynamically. A micro-strain device connected to a wedge interferometer is utilized for this purpose. An empirical formula is selected to represent the variation of birefringence of nylon 6 fibres with draw ratio. This formula is used for fitting the experimental data and for evaluation of non-tabulated values. Microinterferograms are given for illustration.

Interferometric investigation of optical dispersion of blue Cashmeline fibres

Multiple-beam Fizeau fringes in transmission have been applied to investigate the optical dispersion properties of blue Cashmeline fibres. The refractive indices were determined at different wavelengths for light vibrating parallel and perpendicular to the fibre axis. It was observed that both n/sub /// and nperpendicular to follow Cauchy's dispersion relation over the visible range of the spectrum. The constants A and B of Cauchy's formula were estimated. The observed results were interpreted in terms of the axial symmetry of the fibre.

Structural characteristics and optical properties of vestan (polyester) fibres

Refractive indices and birefringence for skin and core changes with strain, produced by different stresses in undrawn vestan fibres, were measured interferometrically. Applications were carried out using multiple-beam Fizeau fringes in transmission to determine the Cauchy's constants and dispersive coefficient for the fibre layers. The resulting data were used to calculate the polarizability per unit volume for each layer. The scanning electron microscope (SEM), optical microscope and He-Ne laser beam were applied to estimate the geometrical parameters of the fibre cross-section. A comparative study between the three methods used for measuring the fibre diameter was made. The effect of temperature on the refractive index and birefringence for each fibre layer has been also investigated. The relationship between temperature and birefringence of the fibres was studied and the thermal coefficient of the refractive index was determined. An empirical formula is suggested to relate temperature and birefringence. Illustrations are given using microinterferograms.

Optical Anisotropy in Mohair Fibers

The diffraction from a He-Ne laser beam was used to measure the dimensional parameters, transverse sectional shape, and area of mohair fibers. Multiple-beam Fizeau fringes in transmission, and double refracting interference microscopy (Pluta polarizing interference microscope) were used to measure the refractive indices and birefringence of the mohair. The double-beam technique was applied to determine the mean re fractive indices for plane polarized light vibrating parallel and perpendicular to the fiber axis and thus the mean birefringence. Two other recent analytical methods were employed to study the optical properties of fibers from the interference patterns pro duced by the formation of multiple-beam Fizeau fringes crossing mohair fibers. These methods were used to determine Cauchy's constants and the thermal coefficient of refractive indices of the skin and core of the mohair. A comparative study of these methods is discussed and illustrated using photomicrographs.

Effect of gamma irradiation on the refractive indices, birefringence and optical absorption of blue Cashmeline fibre

Multiple-beam Fizeau fringes in transmission have been applied to gamma -irradiated blue Cashmeline fibres, to determine their refractive indices for plane-polarised monochromatic light at gamma =5461 AA, vibrating parallel and perpendicular to the fibre axis, and the birefringence over the range from 5 Mrad up to 200 Mrad.

Optical anisotropy in gamma-irradiated fibres under vacuum

The change of optical anisotropy in polymeric fibres by γ-irradiation is suggested to develop a simple method for γ-ray dosimetry. Multiple-beam Fizeau fringes in transmission and in reflection are used in this study for the determination of the refractive indices and birefringence of γ-irradiated Dralon fibres. Variation of the refractive indices of these fibres with the temperature and wavelength of light are also studied. Empirical formulae are suggested to correlate the optical properties of the irradiated fibres with the applied dose. Lorenz-Lorentz equation is applied to calculate the polarizability of the irradiated fibres per unit volume. Illustrations are given by multiple-beam microinterferograms in transmission and in reflection.

The optical behaviour of polyethylene fibres with different draw ratios

Seven samples of polyethylene fibres with different draw ratios were studied by means of the measurement of their refractive indices and birefringence. In this study three independent techniques were used. These techniques were the Becke line, two-beam and multiple-beam Fizeau fringes. Variation of refractive index of the fibre with temperature was determined for two different draw ratios. Applications were carried out in which multiple-beam Fizeau fringes in transmission were used to determine the constants of Cauchy's dispersion formula. The resulting data were utilized to calculate the polarizability per unit volume of the fibre material. Relationships between the optical parameters and the draw ratios are given. The results obtained clarify the effect of the draw ratio on the optical behaviour of polyethylene fibres. Microinterferograms are given for illustration.

Analysis of Refractive Index Distribution in Anisotropic Polymeric Fibers with Regular and Irregular Transverse Sectional Shapes

Three different techniques, the Becke-line method, two beam-interference microscopy, and the application of multiple-beam Fizeau fringes in transmission and reflection, were used to measure the refractive indices for light vibrating parallel and perpendicular to the axis of regular and irregular cross sections. The fibers were bicomponent (nylon 6 and 66), Perlon (polyamide 6), and nylon 6 fibers from an Egyptian manufacturer. Two different formulas were used to determine the indices of refraction for each layer of inhomogeneous fibers. The birefringence and Cauchy constants were also determined. This experimental work demonstrates the potential applications of these two mathematical formulas to obtain accurate results. The advantages of the methods are discussed using microinterferograms.

Interferometric determination of the refractive indices, birefringence and homogeneity of a polymer thin film

An experimental illustration using microinterferometry is given as a qualitative and quantitative method for determining the refractive indices, birefringence and estimating of the homogeneity of polymer thin film. Multiple-beam Fizeau fringes in transmission were applied for sliced polymer of rectangular cross-sectional shape. Thin film optical parameters could be determined from the shape of Fizeau fringes obtained experimentally. The applicability and advantage of this method have been discussed from the point of view of thin film microscopy. Illustrations were made using photomicrographs.

Optical anisotropy in polypropylene fibres as a function of the draw ratio

In this work optical properties of six samples of polypropylene fibres having different draw ratios are measured interferometrically using multiple-beam Fizeau fringes in transmission. These fibres are found to show considerable optical anisotropy. Three independent techniques have been employed to study the optical anisotropy in these fibres. The first technique determined the geometrical parameters of the fibre from its diffraction pattern using a He-Ne laser beam at 632.8 nm. The second is the application of the Becke-line method to determine the refractive indices and birefringence of the fibre's skin. The third is the application of multiple-beam Fizeau fringes in transmission to determine the mean refractive indices and the mean birefringence of these fibres with different draw ratio. The refractive index of the fibre's core is calculated from the predetermined parameters. Relationships between the mean refractive index and the birefringence of fibres with the draw ratio are given and illustrations with microinterferograms are presented.

Birefringence Phenomena in Kidney-shaped Multilayer Fibres

A theoretical treatment of the shape of Fizeau fringes crossing a multilayer fibre of kidney-shaped cross-section is presented. A mathematical expression is derived and used to estimate the refractive indices and the birefringence of Dralon-K polyacrylonitrile fibre. Variation of refractive index with temperature is reported. The resulting data were utilized to calculate the polarizability per unit volume for each layer. Applications are reported in which multiple-beam Fizeau fringes in transmission and reflexion were used, and SEM was employed to estimate the geometrical parameters of the cross-section. Good agreement between the theoretical and experimental results is found.

Stress birefringence in polypropylene fibres

Refractive indices and birefringence changes with strain produced by different stresses in undrawn polypropylene fibres have been measured dynamically by interferometry. A micro-strain device connected to a wedge interferometer has been constructed. Using this wedge interferometer, multiple-beam Fizeau fringes in transmission are made to cross the fibre perpendicular to its axis. As these fringes cross the fibre they suffer a shift, the area enclosed under which is considered to represent the optical path difference integrated across the fibre. It has been found that the relation between strain and birefringence is linear up to strains of 86%. For greater strain the rate of change of birefringence with strain is decreased. Poisson's ratio is calculated over three strain ranges. An empirical formula is suggested to represent the variation of cross-sectional area of polypropylene fibres with draw ratio, and the constants of this formula are determined. Micro-interferograms are given for illustration.

Interferometric Determination of Optical Properties of Bicomponent Fibers

Abstract Both double-beam and multiple-beam interferometry were applied for the determination of refractive indices and birefringence of nylon, 6 sheath, nylon 66 core bicomponent fibers. Double-beam technique was applied to determine the mean refractive indices for plane polarized light vibrating parallel and perpendicular to the fiber axis and the mean birefringence. Multiple-beam Fizeau fringes in transmission and in reflection were used to determine these optical parameters for each component of these fibers.

Optical Properties and Geometrical Parameters of Poly(p-phenylene Terephthalamide) Fibers

Forward scattering of a He-Ne laser beam was used to measure the dimensional parameters, transverse-sectional shape, and area for two different samples of poly( p- phenylene terephthalamide) (PPT) fibers, PRD 49 and Kevlar 49. A double-beam interferometric technique was applied to determine the mean refractive indices for plane polarized light vibrating parallel and perpendicular to the fiber axis, and the mean birefringence was also determined for the two samples of PPT fibers. The area enclosed under the interference fringe shift, when crossing the fiber, represents the path difference integrated across the fiber. The mean values of the transverse-sectional area of fibers measured from the forward scattering of the laser beam were used to calculate the refractive indices and the birefringence of the fibers. Multiple-beam Fizeau fringes in transmission were used to determine the perpendicular refractive indices for each of the two samples of PPT fibers, using the value of the fiber thickness measured by the diffraction method. The obtained values for refractive indices, the birefringence, and diameter of PRD 49 and Kevlar 49 fibers measured by this technique are in a good agreement with previously published values.