共查询到20条相似文献,搜索用时 31 毫秒
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斜光轴面内位移测量的数字散斑相关法研究 总被引:2,自引:0,他引:2
以工程环境中远距离位移和位移场的光学测量为研究课题,分析了远距离斜光轴成像时,像模糊和成像位置变化对白光数字散斑相关方法产生的影响,给出了这两种影响的误差理论计算公式。提出使用参考测量技术克服斜光轴成像位置变化带来影响,给出一种新的远距离斜光轴高精度测量面内位移的方法,在2~50m处作静载挠度测量,其最大相对误差小于1%,测量精度在实验室环境和工程测量环境中都得到了验证。该方法无需共轴光路的测量环境要求,特别适用于桥梁、高速公路立交桥的静载挠度测量等工程应用。使用高速图像采集卡,该方法可应用于斜光轴动态位移测量,拓展了数字散斑相关方法的应用范围。 相似文献
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Multiple-wavelength optical fields on a detecting plane of an interferometer are generated from the interference signals detected for an object surface. The generated optical fields are backpropagated along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the position of the object surface with an accuracy of a few nanometers. 相似文献
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Based on the theory of paraxial electromagnetic beams in anisotropic medium, propagation properties of a linearly polarized confluent hypergeometric (HyG) beam through uniaxial crystals orthogonal to the optical axis are investigated. Analytical expressions are derived for the resultant optical field components. Effects of separate beam parameters together with the ratio of refractive indices of crystals on transversal intensity distributions are revealed by numerical calculations, respectively. It is shown that the beam profile finally converts into an elliptical shape due to influences of anisotropic crystals. Moreover, it is also indicated that through suitable selection of parameters, types of the optical vortices of resultant field would change from a central dark spot to a slight dark ring or an axial shadow during the propagation. These numerical results may provide alternative advantages to the trapping of tiny particles by utilizing HyG beams in practical experiments. 相似文献
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A. H. Gevorgyan 《Technical Physics》2002,47(8):1008-1013
The effect of an applied magnetic field on the optical properties of a layer of a helical periodic medium is studied in view of magnetooptic activity. The case when the radiation is normally incident on the layer and the magnetic field is aligned with the axis of the medium is considered. Irreversibility (nonreciprocity) effects in such a system are discussed. The situations with weak and high anisotropy are investigated. It is shown that the system can function as an optical shutter, optical diode, or one-side reflector. Reasons for the high irreversibility of transmission (reflection) are found. 相似文献
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The procedure of automatic alignment of the four-pass amplifier channel of a UFL-2M facility has been simulated numerically in the presence of aberrations in the optical path. The alignment procedure is based on the “marker” or “reference” method. The control elements are directed by the stochastic parallel gradient algorithm. The order of executing the automatic alignment is determined. The numerical simulation shows the possibility of positioning the beam at the exit from the channel with an accuracy of 1% of the pinhole size in the far field and of 0.1% of the beam aperture size in the near field. It was established that the centering accuracy of the alignment beam in inner pinholes in the presence of optical inhomogeneities in the amplifier channel can be worse than at the exit of the channel. The possibility of symmetrizing the picture of far-field markers has been considered in the case where the position of the optical axis of the channel is unknown. 相似文献
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研究了轴棱锥聚焦像散椭圆高斯光束的光场分布特性,根据菲涅耳衍射积分理论导出了椭圆高斯光束经轴棱锥衍射后的光场分布,通过数值积分给出椭圆高斯光束经轴棱锥聚焦后的近轴光场强度分布情况,将其与圆高斯光束产生的近似Bessel-Gauss场进行比较,发现椭圆高斯光束经轴棱锥聚焦后的光束在一定的传播距离内也具有无衍射特性,且轴上光强分布与圆高斯光束产生的Bessel-Gauss光束的轴上光强分布具有相似的形式,而这种无衍射光场的强度在垂直于光轴的平面上不再是柱对称分布。根据近轴球面波产生近似Bessel光束的最大无衍射距离公式计算了椭圆Bessel-Gauss光束在子午面和弧矢面上的最大无衍射距离,整个光束的无衍射距离由入射到轴棱锥上的椭圆光斑短轴方向的尺寸决定。 相似文献
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Two robust systems for vibration measurements are presented. Both systems are based on low-cost laser diodes. The stability of the optical systems is achieved by implementing the optical system as a holographic optical element (HOE) while using a common-path interferometer concept for the measurement scheme. The former system facilitates real-time simultaneous tracking of vibrations about two axes perpendicular to the optical axis. The latter system is an electronic speckle interferometer working in a differential mode providing whole-field information on the angular deformation about one axis between two states of the object. It will be argued that these concepts will provide compact, self-aligning systems for industrial use due to the inherent possibility of mass fabrication. 相似文献
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V. V. Grishachev 《Physics of the Solid State》2002,44(7):1363-1369
The effect of a magnetic field on the average photorefractive sensitivity of an undoped LiNbO3 crystal is studied by phase-mismatched second-harmonic generation. The experimental data obtained show the photorefractive sensitivity to reverse sign as the external magnetic field exceeds B 1=?0.38±0.04 T. The magnetic field is oriented perpendicular to the crystal optical axis and to the plane of laser radiation polarization. The variation of the photorefractive sensitivity is associated with paramagnetic iron centers, whose photoionization probability depends on the direction of their magnetic moment relative to the optical axis. 相似文献
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L. G. Gasparyan V. P. Mkrtchyan T. K. Dadalyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2017,52(3):271-275
The influence of external electric field on the anisotropy of a layer of nematic liquid crystal (NLC) was investigated by means of X-Ray interferometric method. It was shown that in Xray range of the spectrum NLC E7 is a positive anisotropic medium. The decrements of a layer of NLC subjected to the electric field were calculated. As a result of reorientation of NLC molecules perpendicular to the cell substrate, the decrements prove equal for cases when the optical axis of a sample was initially perpendicular or parallel to the X-ray beam polarization vector. 相似文献
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И. С. Желудев 《Czechoslovak Journal of Physics》1966,16(5):368-381
The necessary and sufficient conditions for the existence of the direct and inverse piezoelectric effect in crystals and textures are deduced. It is found that under certain conditions the piezoelectric properties in crystals of certain classes are richer than those obtained from the piezoelectric tensor. The results are given of the piezoelectric polarization of quartz in the direction of the optical axis and the excitation of oscillations of the plates perpendicular to the optical axis when the field is applied in the direction of the optical axis. 相似文献
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The conditions for the realization of absorption optical bistability under the simultaneous action of two (radiative and nonradiative) mechanisms of recombination of free charge carriers are investigated. It is shown that, in the diffusion mechanism of stream of free electrons from the beam axis, the temperature dependence of radiative recombination does not expand the temperature range of the thermostat in which the optical bistability occurs. A scheme is proposed with application of an external transverse electric field, which makes it possible to realize absorption optical bistability at any ambient temperature. An important advantage of this scheme is the conservation of the state of a bistable system after the action of a light pulse and a significant decrease in the energy spent on cooling of the medium. 相似文献
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It has been shown that nonlinear near-field optical resonances occur in diatomic nanostructures consisting of identical or different two-level atoms in the presence of a radiation field when the dipole-dipole interaction is taken into account. The frequencies of these resonances depend strongly on the intensity of the external optical radiation, on the initial conditions, on the polarization of the external field with respect to the axis of the nanostructure, and on the interatomic distance. The interatomic interaction is taken into account beyond perturbation theory. For this reason, the effective polarizabilities of the atoms of the nanostructure are expressed in terms of the polynomials of both the interatomic distance and the electric field strength of the external optical wave. A “falling tower” effect that is caused by the nonlinear behavior of the local dipole moments of atoms in the nanostructure is predicted. 相似文献
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An optical technique to align laser beam with the axis of a rotating stage is proposed for laser fabrication of circular microstructures. The laser beam is first aligned parallel to the rotation axis and subsequently adjusted to coincide with the axis. An optical arrangement consisting of two quadrant photodiodes for the x- and y-directions and a specially designed beam splitter is utilized for the alignment. Mathematical modeling of the alignment system is carried out to estimate alignment errors caused by misalignment of mirror surfaces in the beam path. It is shown that parallelness of the laser beam to the rotation axis is a key factor to reduce alignment errors. The proposed method was applied to a microstereolithography system and proved that the laser beam can be aligned within a distance of about 25 μm from the rotation axis. 相似文献
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It is shown that a rotation ? and a deformation κ of the optical indicatrix appear during the transverse magnetic field-induced phase transition in hematite. Analytic expressions for ? and κ are deduced from the magnetization-dependent electromagnetic energy in the crystal. It is shown that during the phase transition, induced by increasing the temperature, the electromagnetic energy in the crystal. It is shown that during the phase transition, induced by increasing the temperature, the antiferromagnetic vector L = M1 - M2 is rotating from the three-fold C3 axis toward the basal plane, which implies that the main axis of the optical indicatrix is not aligned in a general case with the magnetic field or the crystallographic axis although the magnetic moment (M1 + M2) is always parallel to the field. The linear magnetic birefringence is very sensitive to the magnetic phase in hematite, as described in previous experimental work, but the present analysis shows that a direct determination of the transverse field-induced phase transition can be obtained in hematite, by means of a magnetooptical method, only when large and non-uniform rotation (up to ninety degrees) and variation of the shape of the indicatrix are taken into account. 相似文献
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An approximate pattern of calculation of the field behavior in waveguides of variable radius is proposed. It is based on the
assumption of a slow dependence of the radius on the longitudinal coordinate and is reduced to the solution of an ordinary
differential equation. The dependences of the waveguide transmission on the frequency of radiation, entrance and exit radii,
as well as the rate of radius variation along the axis are studied. The analysis is carried out within the range of parameters
typical for optical fibers used in optical near‐field microscopy. It is shown that the increase in the rate of radius variation
with the longitudinal coordinate will cause the transmission coefficient of the tapered waveguide to increase. 相似文献