共查询到20条相似文献,搜索用时 31 毫秒
1.
A. M. Hamed 《Pramana》2008,70(4):643-648
A quadratic model is suggested to describe the fringe shift occurred due to the phase variations of uncladded glass fiber
introduced between the two plates of the liquid wedge interferometer. The fringe shift of the phase object is represented
in the harmonic term which appears in the denominator of the Airy distribution formula of Fabry-Perot’s interferometer. A
computer program is written to plot the computed fringe shifts of the described model.
An experiment is conducted using liquid wedge interferometer where the fiber of a nearly quadratic thickness variation is
introduced between the two plates of the interferometer. The obtained fringe shift shows a good agreement with the proposed
quadratic model. Also, it is compared with the previous theoretical shift based on ray optics of semi-circular shape.
相似文献
2.
Multiple-beam interference fringes applied to investigate the index profile of the optical fiber dip
H. A. El-Hennawi Fouad El-Diasty H. El-Ghandoor Mona A. Soliman 《Optical and Quantum Electronics》2012,43(1-5):35-48
A numerical-based phase shift method is presented to study optical fibers having a dip in the refractive index profile at the center of the core. Mathematical expressions for the shape of multiple-beam Fizeau fringes crossing a graded-index optical fiber (GRIN) comprising a central graded-index dip or GRIN fiber with a constant refractive index dip, immersed in a silvered liquid wedge, are derived. The index profile parameters of the central dip are determined by comparing the theoretical fringe shape across the fiber cross-section and the experimental fringe shape obtained from micro-interferograms of the wedge interferometer. 相似文献
3.
4.
Rapid extraction of the phase shift of the cold-atom interferometer via phase demodulation 下载免费PDF全文
《中国物理 B》2015,(11)
Generally, the phase of the cold-atom interferometer is extracted from the atomic interference fringe, which can be obtained by scanning the chirp rate of the Raman lasers at a given interrogation time T. If mapping the phase shift for each T with a series of measurements, the extraction time is limited by the protocol of each T measurement, and therefore increases dramatically when doing fine mapping with a small step of T. Here we present a new method for rapid extraction of the phase shift via phase demodulation. By using this method, the systematic shifts can be mapped though the whole interference area. This method enables quick diagnostics of the potential cause of the phase shift in specific time. We demonstrate experimentally that this method is effective for the evaluation of the systematic errors of the cold atomic gravimeter. The systematic phase error induced by the quadratic Zeeman effect in the free-falling region is extracted by this method. The measured results correspond well with the theoretic prediction and also agree with the results obtained by the fringe fitting method for each T. 相似文献
5.
We present a new white-light interferometric technique to measure the group index of holey fibres over a wide wavelength range. The technique utilizes an unbalanced Mach–Zehnder interferometer with a fibre under test of known length placed in one of the interferometer arms and the other arm with adjustable path length. In a first step, the differential group index of the fibre is measured over a wide wavelength range. In a second step, the fibre is replaced by the reference sample of known thickness and group dispersion to determine precisely the group index of the fibre at one specific wavelength. The group index as a function of wavelength is measured for two different holey fibres, one made of pure silica glass and the other made of SK222 glass. For both fibres, the wavelength dependence of the group index of the outer cladding and modes supported by the fibre is measured. 相似文献
6.
Suezou Nakadate 《Optics and Lasers in Engineering》1997,26(4-5)
A digital speckle pattern shearing interferometer is presented which utilizes a single birefringent wedge. Two orthogonally polarized images of an object measured are sheared by the wedge, and the bias phase difference between two polarized images is shifted by translating the wedge. The phase shifting technique applied to speckle pattern shearing interferometry makes it possible to analyze a slope and surface strain numerically. The fringe formation in the present interferometer is analyzed with statistical theory. Experimental results are also presented in two cases: (1) measurement of a slope and normal displacement with a single illumination; (2) simultaneous and separate measurement of a slope and surface strain with two symmetrical illuminations. 相似文献
7.
The common camera lens usually includes the spherical glass/plastic lens and aspheric glass/plastic lens. However, spherical/aspheric shape measurement is still a key problem in the process of optical lens fabrication. At present, the in-process measurement of spherical/aspheric shape is conducted mainly by the probe-contacting method. But after a long time, its probe could be scratched severely and cause some big errors. Laser shearing interferometry is a good substitute to some degree. Nevertheless, it is not convenient for general shearing interferometer to carry out the in-process measurement because it is only suitable for certain kind of spherical/aspheric with respect to aperture or asperity. Here a new lateral shearing interferometer is proposed to solve the described problems. It is based on two Jamin plates and rotatable prism pairs which are used not only for shearing displacement and direction, but also for fringe period and tilt degree, in order to meet requirements of various spherical/aspheric shapes or asperities. The new interferometer features a simple optical structure and two symmetric light paths, which makes its system with minimal error. The relation between shearing displacement, fringe period and prism angle of rotation is given in this paper. And the error source is primarily from the manufacture errors of prisms and plates. The final experiments show that one can achieve good-quality fringe patterns according to the requirement of measurement, concerning the shearing direction, shearing displacement, fringe period, tilt degree, etc. 相似文献
8.
Multiple-beam interference fringes of equal chromatic order are produced in air and liquid sample interferometric gaps. The two gaps are of the same thickness and simultaneously enclosed in a wedge interferometer. A single shot interferogram containing fringes in the two gaps is sufficient to deduce the needed experimental data. Locations of the fringe maxima, in the two gaps, are introduced in a non-numerical procedure for determining the gap thickness and the liquid-phase refractive indices across the visible spectrum. The method has been used for measuring the phase refractive indices of human blood-serum, saliva, sweat, urine and water liquids. A third-order polynomial dispersion relation is applied for fitting the measured phase indices. Group refractive indices have been derived and fitted to the same dispersion formula. 相似文献
9.
Slightly dispersive white-light spectral interferometry to measure distances and displacements 总被引:1,自引:0,他引:1
A new spectral-domain interferometric technique of measuring distances and displacements is realized when the effect of low dispersion in a Michelson interferometer, which comprises two coated plates of a beam splitter and a compensator, is known and the spectral interference fringes are resolved over a wide wavelength range. First, processing the recorded spectral interferograms by an adequate method, the unmodulated spectrum, the spectral fringe visibility function and the unwrapped phase function are obtained. Then, knowing the dispersion relation for the fused-silica plates, the ambiguity of the unwrapped phase function is removed and the thickness of fused silica and the nonlinear phase function due to the effect of the coatings are determined by using a new procedure. It is based on the linear dependence of the overall optical path difference between interferometer beams on the refractive index of fused silica. Once the thickness and the nonlinear phase function are known, the positions of the interferometer mirror are determined precisely by a least-squares fitting of the theoretical spectral interferograms to the recorded ones. 相似文献
10.
J. D. R. Valera J. D. C. JonesD. P. Towers C. H. Buckberry 《Optics and Lasers in Engineering》1997,26(4-5)
An optical fibre based, speckle shearing interferometer is described. The instrument uses a highly birefringent optical fibre to illuminate a test object with equal intensities of light guided by the orthogonal polarisation eigenstates of the fibre. A Wollaston prism is used to obtain two sheared images with adjustable shear. Optical phase changes between the sheared images are readily achieved, without mechanical movement of components, by straining the optical fibre. Object strain determination, by fringe analysis with phase stepping techniques, is readily achieved. Vibration analysis by heterodyning is also reported. 相似文献
11.
Air, liquid and solid sample interferometric gaps of the same thickness and simultaneously enclosed in a wedge interferometer are used to produce fringes of equal chromatic order. A mica sample of dimensions 2×5 mm2 and an immersion liquid of the same refractive index are used. A single shot interferogram containing fringes in the three gaps is sufficient to deduce the needed experimental data. Locations of fringe maxima are introduced in a numerical procedure to retrieve the sample and liquid refractive indices across the visible spectrum. The numerical procedure is based on a simple dispersion function of wavelength and wavenumber. A modified two-term Sellmeier dispersion formula has been used for fitting the experimental data and deducing the needed dispersion parameters. 相似文献
12.
In this paper, we present an interferometric method to determine the refractive index profile in graded-index planar waveguides. To begin, part of the soda-lime glass substrate surface was coated with aluminum and then was immersed in molten AgNO3 to fabricate a planar waveguide on the uncoated part of the surface. After the ion exchange, the coating was removed. Then, the sample was polished obliquely along the boundary between the ion-exchanged and non-ion-exchanged regions, to form a wedge. Thereafter, it was placed inside a Mach–Zehnder interferometer. The fringe pattern was analyzed using the well-known Fourier method and the refractive index profile was determined. The sample preparation, data analysis and experimental results are presented. 相似文献
13.
O. Frazão C. Correia J.M. Baptista M.B. Marques J.L. Santos 《Optics Communications》2008,281(22):5601-5604
This work presents two distinct configurations based on phase-wavelength conversion using a ring fibre laser with two different long period gratings interferometer topologies. The sensors are interrogated by analysing the wavelength change of the emission laser, which is directly dependent on the interferometer phase change. The first configuration integrates a Mach-Zehnder interferometer, which is based on a pair of long period gratings and is used as sensing head for bending radius and longitudinal strain measurement. The second configuration, comprehends a Michelson interferometer, which is based on a single LPG and a fibre end mirror and is used as a liquid level sensor or as an optical refractometer. 相似文献
14.
A. A. Hamza M. A. Mabrouk W. A. Ramadan M. A. Shams-Eldin 《Optics Communications》2001,200(1-6):131-138
The core–cladding refractive index difference Δn and the index gradient profile parameter of the graded index (GR-IN) optical fibre has been determined. The curve representing the real path, in the core region, due to refraction of the beam and the change in the exit wavefront are considered. Multiple-beam Fizeau fringes and two-beam interference Pluta polarizing microscope, are used for this investigation. A new method, based on a derived mathematical expression, is used with a prepared computer program to estimate the fringe shift inside GR-IN of the fibre core. The estimated and experimental values of the fringe shift, along the core radius, are used to obtain the refractive index profile of the optical fibre. A comparison between the new method and a previous model considering the refraction has been shown. Microinterferograms are given for illustrations. 相似文献
15.
We report a simple, compact electronic speckle-pattern interferometer (ESPI) incorporating holographic optical elements (HOEs) for the study of out-of-plane vibration. Reflection and transmission HOEs provide reference and object beams in the interferometer. The alignment difficulties with conventional ESPI systems are minimized using HOEs. The time-average ESPI subtraction method is used to generate the fringe pattern and remove background speckle noise by introducing a phase shift between consecutive images. The amplitude and phase maps are obtained using path-difference modulation. 相似文献
16.
The intensity variation of bright and dark fringes in Young's double slit experiment shows that a light beam propagating through the focus of a lens experiences a phase shift (called the Gouy phase shift [Gouy CR. Acad Sci Paris 1890;110:1251]) with respect to its plane wave counterpart. The additional phase change of π introduced on focusing the light beam and then further propagating it in one arm of the interferometer changes a bright fringe into a dark fringe and vice-versa. We have, thus, made direct visualization of the Gouy phase shift by a simple experiment. 相似文献
17.
The fringe profiles from a two beam interferometer with phase feedback are almost unambiguous over a range of 2π or more. This allows phase and therefore surface profile to be determined directly from output intensity of an interferometer. In this paper we describe how feedback can be applied to a polarisation Sagnac common path interferometer using a parallel aligned nematic liquid crystal spatial light modulator. Initial experiments have shown that the device is capable of measuring profiles to accuracies greater than one tenth of a wavelength. 相似文献
18.
Simultaneous measurement of the phase and group indices and the thickness of transparent plates by low-coherence interferometry 总被引:3,自引:0,他引:3
We propose and demonstrate a novel technique for simultaneous measurement of the phase index, n(p) , the group index, n(g) , and the thickness, t , of transparent plates by use of a low-coherence interferometer. The output light from a superluminescent diode is focused upon the front plane of a transparent plate that is used as the sample. The sample stage is subsequently moved until the light is focused upon the rear plane of the plate. Measurement of the stage movement distance and the corresponding optical path difference allows us to determine both n(p) and n(g) . By placing the sample between two glass plates, we measured n(p) , n(g) , and t simultaneously, with an error of 0.3% or less, for nearly 1-mm-thick transparent plates, including glass and electro-optic crystals. 相似文献
19.
We design a fringe-variable Jamin interferometer to detect the reversed domain of a ferroelectric crystal in real time. In contrast to the Mach-Zehnder interferometer, this setup is compact and tunable in fringe frequency. In experiments, we use it to detect the partly reversed domains of Stoichiometric LiTaO3 (SLT). Selecting the proper fringe cycle, we can estimate the average phase shift between the original and reversed domains through eyeballing. Furthermore, in the interferogram processing, we use the FFT methods to reconstruct the phase according to the original fringe and deformed fringe, and obtain the phase variance at the domain wall. The results show that the average phase variance at the domain wall is in good agreement with the theoretical value. 相似文献