共查询到20条相似文献,搜索用时 26 毫秒
1.
Optimization of laser light scatter detection technique based on the geometrical optics method for measuring the size, velocity and refractive index of spherical particles was performed. A new optical orientation for extended phase-Doppler anemometry (EPDA) had been developed to improve the accuracy of particle material recognition in multiphase flow. The effects of both the intensity and phase factor of the reflected and refracted light were examined. The inverse sign of the phase factors from the refracted light and reflected light resulted in a (2π–φ) effect on phase determination. This was used for minimizing and validating the errors in the refractive index measurements of large particles. Furthermore, optimization results were compared with the results of simulation based on the generalized Lorenz–Mie theory (GLMT). A newly developed signal validation scheme was also described in detail. The scheme was used to reject the inaccurate data in order to further improve the accuracy of the recognition. 相似文献
2.
Fabrice Onofri Damien Blondel Grard Grhan Grard Gouesbet 《Particle & Particle Systems Characterization》1996,13(2):104-111
After having recalled basic theoretical results concerning the extension of generalized Lorenz-Mie theory to the case of multilayered spheres, results connected with phase-Doppler anemometry are considered, showing the influence of Gaussian beam intensity profiles on the light scattering properties of these particles. Particular emphasis is placed on the case of water-coated carbon core particles, for which the possibility of obtaining simultaneous size measurements of the core and outer diameters is discussed. The sensitivity of the technique to particles with a refractive index profile is also considered, showing that this technique is more sensitive to changes in the average refractive index of the particles than to refractive index profiles, such as produced by high pressure and temperature stresses, at least for the studied geometry. 相似文献
3.
Fabrice Onofri Thierry Girasole Grard Grhan Grard Gouesbet Günter Brenn Joachim Domnick Tian-Hua Xu Cameron Tropea 《Particle & Particle Systems Characterization》1996,13(2):112-124
The principle of the dual burst technique (DBT) based on phase-Doppler anemometry (PDA) is proposed for simultaneous particle refractive index, size and velocity measurements. This technique used the trajectory effects in PDA systems to separate the two contributions of the different scattering processes. In the case of forward scattering and refracting particles, it is shown that from the phase of the reflected contribution, the particle diameter can be deduced, whereas from the refracted contribution the particle refractive index and velocity can be obtained. Furthermore, the intensity ratio of these two scattering processes can be used for absorption measurements. Simulations based on generalized Lorenz-Mie theory and experimental tests using monodispersed droplets of different refractive indices and absorption coefficients have validated this technique. 相似文献
4.
Heinz-E. Albrecht Marcus Wenzel Michael Borys 《Particle & Particle Systems Characterization》1996,13(1):18-26
The influence of the measurement volume can be investigated by using extended geometrical optics, which is based on geometrical optics by including the amplitude and phase distribution in the laser beam. The dynamics in phase Doppler anemometry can be analysed, in addition to effects of the particle size-dependent detection volume. Extended geometrical optics has been developed as a powerful tool to investigate these influences for each order of light scattering separately. Phase errors caused by Gaussian-beam intensity distribution and the curvature of the wave fronts beyond the beam waist can easily be calculated. According to Part 1 (Reflective Mode Operation), the influence of the particle trajectories on measured phase and mass concentration is simulated for refractive mode operation. 相似文献
5.
根据波动光学的理论,对菲涅耳近场衍射公式误差相位的影响进行了分析。以单缝衍射为例,讨论了误差相位与计算精度的联系。结合菲涅耳线波带片焦面光强分布的计算,对比了菲涅耳衍射公式与基尔霍夫衍射公式的计算结果,说明在不满足误差相位近似条件下使用菲涅耳衍射公式带来的影响。最后对影响波带片焦面光强分布的几个因素进行了讨论。 相似文献
6.
In the present work, lecture demonstration of Fresnel diffraction by a slit and half-plane with the use of modern scientific
means of optical experimentation is described. The developed software allows light diffraction to be modeled on a personal
computer depending on the wavelength, slit width, and distance from the slit (half-plane) to the screen and simultaneously
a graphic method of calculating the field amplitude with the help of the Cornu spiral to be demonstrated. A photodetector
system built around a video camera controlled by a personal computer is used to register an actual diffraction pattern. The
experimental intensity distributions are compared with the theory. The integrated approach allows the efficiency of comprehension
of complex diffraction phenomena in wave optics to be increased.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 9–15, June, 2005. 相似文献
7.
Hans-Henrik von Benzon Preben Buchhave 《Particle & Particle Systems Characterization》1994,11(1):55-62
Using a computer model based on Lorenz-Mie and generalized Lorenz-Mie theory, various optical confiugurations of a phase-Doppler system were analysed with regard to their suitability for diameter measurements in the sub-micron range. The major concern in this size range is multi-valuedness of the phase-diameter characteristic, the relatively small signal-to-noise ratio obtained with the very low scattered intensity and the small value of the phase difference to be measured. It is shown numerically and by experiment that for particles in a free stream the multi-valuedness and the shot noise need not prohibit measurements in the sub-micron size range. The major source of phase error results from light scattered form objects or material other than the particle inside the measuring volume. Using an optical set-up with nearly counter-propagating incident beams and a large angle between the detectors, measurements were obtained for particle diameters down to 200 nm, and it is estimated that with some improvements in receiver optics measurement down to 100 nm will be possible. 相似文献
8.
Diffraction properties of the transmission phase grating are analyzed in terms of the Fourier optics theory. The analysis results show that the diffraction intensity distribution of the transmission phase grating is closely related to the optical thickness of the grating and the wavelength of the incident light, and not only determined by the grating's period and slit width. For monochromatic incident light, more than 80% of the diffraction energy will concentrate to the first diffraction order under certain conditions. For white incident light, the energy of the first order of diffraction spectrum may be much higher than other orders. Based on these results, some possible applications of the transmission phase grating are discussed. 相似文献
9.
When applying phase-Doppler anemometry (PDA) to measurements of mass flux, one has to deal with errors caused by multiple scattering effects within a PDA measurement volume. Theoretical research on the influence of multiple scattering effects on PDA is more promising than experimental work, because each error source can be treated separately. Therefore, we have simulated multiple scattering effects occurring in the measurement volume by extending a method for light scattering calculations to Gaussian beams: the multiple multipole method (MMP). The current version of our computer program is able to simulate PDA with any set-up consisting of Gaussian beams, using one or more homogeneous particles with arbitrary shape and movement and two detectors at any position and with an arbitrarily shaped aperture. In this paper we have concentrated on multiple scattering effects caused by two equally sized spheres, a case which is frequently found in atomizalion. 相似文献
10.
《中国物理 B》2015,(5)
The high-power laser beam in the final optics assembly of high-power laser facilities is often modulated by contamination particles, which may cause local high light intensity, thereby increasing the filamentary damage probability for optical components. To study the general design basis for a final optics assembly to decrease the risk of filamentary damage,different-sized contamination particles deposited on a component surface are simulated to modulate a 351-nm laser beam based on the optical transmission theory, and the corresponding simulation results are analyzed statistically in terms of the propagation characteristic and the light field intensity distribution of the modulated laser beam. The statistical results show that component thickness and distance between components can to some extent be optimized to reduce the appearance of local high light intensity, and the general design basis of component thickness and arrangement are given for different control levels of particle sizes. Moreover, the statistical results can also predict the laser beam quality approximately under the existing optics design and environmental cleanliness. The optimized design for final optics assembly based on environmental cleanliness level is useful to prolong the lifetime of optics and enhance the output power of high-power laser facilities. 相似文献
11.
Eccentric photorefraction usually is used as early eyesight diagnostic test of infants and small children. Unlike currently approved geometrical optical model of eccentric photorefractometer, the crescent formation and the light-intensity distribution in the pupil image of a myopic eye are analyzed by Fourier optics with the assumption of an isotropic scattering retina. In the case of little circular light source and rectangular slit, the simulation results of different myopic diopters are obtained by geometrical optical theory and Fourier optics respectively. It is found that the simulation results by Fourier optics are similar as those obtained by geometrical optics, and all simulations are almost corresponding to the experimental result.The result demonstrates that the new method presented here is feasible. 相似文献
12.
菲涅耳双棱镜干涉在相衬成像和全息显微术中有重要应用。为了促进其应用,本文从信息光学角度研究双棱镜干涉,首先利用光场与脉冲响应函数之间的关系,理论导出了菲涅耳双棱镜干涉条纹强度公式,分析并讨论了狭缝缝宽及狭缝到双棱镜距离对菲涅耳双棱镜干涉条纹的影响,狭缝宽度大于0. 1 mm时,干涉条纹分辨率变差。接着给出了改变狭缝宽度(变化量为0. 08 mm)和改变狭缝到双棱镜的距离(从8 cm变化到12 cm)的实验结果,理论分析和实验结果一致。该结果有助于促进菲涅耳双棱镜干涉在相衬成像等领域的应用。 相似文献
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14.
Heinz-E. Albrecht Michael Borys Marcus Wenzel Thomas Wriedt 《Particle & Particle Systems Characterization》1994,11(4):339-344
In phase Doppler anemometry (PDA), phase difference errors are caused by the Gaussian intensity distribution of the laser beam and the curvature of the phase fronts outside of the beam waist. This results in erroneous particle sizes. Based on a physical analysis by geometrical optics [1], this phase difference error is evaluated for reflected mode operation (Part I) and for refracted mode operation (Part II). By varying the particle trajectories statistically, the error in determining the particle size and the mass flow can be simulated. By the method described the error in the measured phase difference can easily be estimated. 相似文献
15.
Liquid crystal spatial light modulator (LC-SLM) has a series of attractive characteristics as a wavefront corrector in adaptive optics system such as compactness, high density integration, low cost and possibility of batch production. However it also suffers from several drawbacks such as low light efficiency. We present an analysis of the light efficiency of the phase by only using LC-SLM for wavefront corrector in AO system. The factors of polarization sensitive, pixel grid structure, phase quantization and limited phase stroke are discussed in theory. Simulation results are given based on a math model of a LC-SLM. The intensity variation results from pixel structure are measured. The light efficiency of the LC-SLM is tested for generating a series of Zernike aberrations. The effect of phase wrapping method is analyzed and tested. We demonstrate that the light efficiency reduces these factors. Experiment results from the use of the phase only liquid crystal spatial light modulator confirms these conclusions. 相似文献
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18.
The plenoptic camera is a single lens stereo camera which can retrieve the direction of light rays while detecting their intensity distribution. In this paper, to reveal more truths of plenoptic camera imaging, we present the wavefront analysis for the plenoptic camera imaging from the angle of physical optics but not from the ray tracing model of geometric optics.Specifically, the wavefront imaging model of a plenoptic camera is analyzed and simulated by scalar diffraction theory and the depth estimation is redescribed based on physical optics. We simulate a set of raw plenoptic images of an object scene, thereby validating the analysis and derivations and the difference between the imaging analysis methods based on geometric optics and physical optics are also shown in simulations. 相似文献
19.
Shohji Tsushima Fumiteru Akamatsu Masashi Katsuki Yukio Mizutani Yong-Dae Cho 《Particle & Particle Systems Characterization》1997,14(5):225-232
The objectives of the present study were to clarify the influence of flames on phase-Doppler anemometry (PDA) and to consider quantitatively the accuracy of measured sizes and velocities using a known-size polystyrene particle and a Bunsen burner placed in the optical path in PDA simulating the variation of refractive index in a combusting field. It was found that fluctuations of a flame had some influence on the measurement, especially on size, while the velocities obtained in these experiments showed little influence of the flame. Furthermore, a compensation procedure for the error was discussed by comparing the scattered data in size measurement with the displacement of incident laser beams. As a result, it was found that the displacement of the laser beams can be related to the degree of errors caused by the influence of a flame on the optical path in PDA. 相似文献
20.
In this paper we presented theoretical predictions of
light diffraction by complex acoustic fields such as: two adjacent and
superposed ultrasonic beams or ultrasound of cylindrical symmetry. The
numerical calculations of light intensity of diffraction orders were
performed by means of two methods: Nth Order Approximation (NOA) and
Successive Diffraction Model (SDM) based on Fourier optics. The latter
technique involves dividing the ultrasonic field into several adjacent
sections provided that in each section the interaction of light and
ultrasound is considered to fulfill Raman-Nath approximation. Propagation of
light inside and behind the region with ultrasonic wave was described within
the formalism of Fourier optics so that only both transfer and transmission
functions had to be appropriately defined. It was revealed that SDM method
based on Fourier optics might be applied in the studies of acousto-optic
interaction in the cases of complex ultrasonic fields. 相似文献