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1.
Traditional camera calibration is based on the pinhole model, which is an approximation algorithm using untrue geometrical
assumptions and giving a single lumped result for the multiple optical elements in a camera. To provide an alternative method
of camera calibration, we extend the traditional 2×2 matrix-based paraxial raytracing method to 6×6 in order to trace paraxial
rays by using the first-order Taylor series expansion of Snell’s laws. Then we establish the geometric relationship between
images and objects. Compared with the Snell’s Law camera calibration model of our previous work, the paraxial model offers
explicit analytical sensitivity analysis for the mathematical manipulation of problematical conditions. Compared with the
existing pinhole model, the proposed method, in addition to five intrinsic and six extrinsic parameters, gives the position
parameters of each optical element of the camera system. 相似文献
2.
Collective surface plasmon resonance (SPR) excitations in an ordered array of silver nanoshells have been theoretically studied
using generalized Mie theory. Near- and far-field radiative coupling between the nanoshells in the array result in a non-monotonic
shift of the collective SPR band. When the distance between the shells in the array approaches that of the collective SPR
wavelength, we observe narrowing of the collective SPR band due to constructive interference between the scattered electric
field from the particles in the array. Further increase of the distance between the nanoshells in the array leads to destructive
interference and broadening of the collective SPR band. 相似文献
3.
F. Albertin A. Franconieri M. Gambaccini D. Moro F. Petrucci S. Chiozzi 《Applied Physics A: Materials Science & Processing》2009,96(2):503-510
Monochromatic X-ray sources can be used for several applications, like in medicine or in studying our cultural heritage. We
are investigating imaging systems based on a tuneable energy band X-ray source, to obtain an element mapping of painting layers
using the K-edge technique.
The narrow energy band beams are obtained with conventional X-ray source via Bragg diffraction on a mosaic crystal; such an
analysis has been performed at different diffraction angles, tuning the energy to investigate spectra of interest from the
artistic point of view, like zinc and copper. In this paper the characteristics of the system in terms of fluence rate are
reported, and first results of this technique on canvas samples and painting are presented. 相似文献
4.
C. Michail A. Toutountzis S. David N. Kalyvas I. Valais I. Kandarakis G. S. Panayiotakis 《Applied physics. B, Lasers and optics》2009,95(1):131-139
The aim of the present study was to measure the imaging transfer characteristics and the luminescence efficiency (XLE) of
a Lu2SiO5:Ce (LSO:Ce) powder scintillator for use in X-ray mammography detectors. An LSO:Ce powder scintillating screen, with a coating
thickness of 25 mg/cm2, was prepared in our laboratory. The imaging performance of the screen was assessed by experimental determination of the
modulation transfer function (MTF) and the detective quantum efficiency (DQE) as well as single index image quality parameters
such as noise equivalent pass band (Ne) and informational efficiency (n
I). A theoretical model, describing radiation and light transfer, was fitted to experimental MTF values in order to estimate
optical properties of the scintillator. Screen irradiation was performed under exposure conditions employed in mammographic
applications (27 kVp, 63 mAs). MTF was determined by the square wave response function (SWRF) method. Results showed that
LSO:Ce exhibits high MTF and DQE values, which are comparable to those of the commercially used Gd2O2S:Tb. Considering our image quality parameters and luminescence efficiency results as well as the fast response of the LSO:Ce
scintillator screen (40 ns), this material can be considered for use in X-ray mammographic detectors. 相似文献
5.
A. Bartnik H. Fiedorowicz R. Jarocki J. Kostecki R. Rakowski M. Szczurek 《Applied physics. B, Lasers and optics》2008,93(4):737-741
In this paper a possibility of performing fluorescence experiments in extreme ultraviolet (EUV) using a laboratory EUV source
was demonstrated. Usually such measurements are performed using third-generation synchrotrons because of extremely low probability
of fluorescence in this wavelength range. In this work a 10 Hz laser-plasma EUV source based on a gas puff target was used.
Fluorescent radiation from Al and Si was registered. Despite relatively low spectral resolution, some differences in Si spectra
coming from different kind of samples were revealed. 相似文献
6.
Guido Zavattini Encrico Calloni 《The European Physical Journal C - Particles and Fields》2009,62(3):459-466
Low energy non-linear QED effects in vacuum have been predicted since 1936 and have been subject of research for many decades.
Two main schemes have been proposed for such a ‘first’ detection: measurements of ellipticity acquired by a linearly polarized
beam of light passing through a magnetic field and direct light–light scattering. The study of the propagation of light through
an external field can also be used to probe for new physics such as the existence of axion-like particles and millicharged
particles. Their existence in nature would cause the index of refraction of vacuum to be different from unity in the presence
of an external field and dependent of the polarization direction of the propagating light. The major achievement of reaching
the project sensitivities in gravitational wave interferometers such as LIGO and VIRGO has opened the possibility of using
such instruments for the detection of QED corrections in electrodynamics and for probing new physics at very low energies.
We show that it is possible to distinguish between various scenarios of new physics in the hypothetical case of detecting
unexpected values. Considering the design sensitivity in the strain of the near future VIRGO+ interferometer leads to a variable
dipole magnet configuration such that B
2
D≥13000 T2 m
for a ‘first’ vacuum non-linear QED detection. 相似文献
7.
8.
Numerical simulations are used to study how fiber supercontinuum generation seeded by picosecond pulses can be actively controlled
through the use of input pulse modulation. By carrying out multiple simulations in the presence of noise, we show how tailored
supercontinuum spectra with increased bandwidth and improved stability can be generated using an input envelope modulation
of appropriate frequency and depth. The results are discussed in terms of the nonlinear propagation dynamics and pump depletion. 相似文献
9.
Jeffrey Chou Kyoungsik Yu David Horsley Brian Yoxall Sagi Mathai Michael R. T. Tan Shih-Yuan Wang Ming C. Wu 《Applied Physics A: Materials Science & Processing》2009,95(4):973-982
We present a free-space optical interconnect system capable of dynamic closed-loop optical alignment using a microlens scanner
with a proportional integral and derivative controller. Electrostatic microlens scanners based on combdrive actuators are
designed and characterized with vertical cavity surface emitting lasers (VCSELs) for adaptive optical beam tracking in the
midst of mechanical vibration noise. The microlens scanners are fabricated on silicon-on-insulator wafers with a bulk micromachining
process using deep reactive ion etching. We demonstrate dynamic optical beam positioning with a 700 Hz bandwidth and a maximum
noise reduction of approximately 40 dB. Eye diagrams with a 1 Gb/s modulation rate are presented to demonstrate the improved
optical link in the presence of mechanical noise. 相似文献
10.
V. A. Bernshtam Yu. Ralchenko Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):319-320
We show that the criticism [Eur. Phys. J. D 49, 167 (2008)] of our
empirical formula for electron-impact ionization of atomic ions [J. Phys B. 33, 5025 (2000)] is unjustified. 相似文献
11.
N. Kejalakshmy B. M. A. Rahman A. Agrawal T. Wongcharoen K. T. V. Grattan 《Applied physics. B, Lasers and optics》2008,93(1):223-230
A modal solution approach based on the powerful, finite element method (FEM) using a full-vectorial H-field formulation has been used to determine the single-mode operation of a photonic crystal fiber (PCF). The modal solution
of the fundamental space-filling mode has also been obtained to identify the cutoff conditions of the waveguide modes. The
FEM, with the perfectly matched layer boundary condition, has been developed and employed to characterize the leakage loss
and the differential loss between the polarized modes of a PCF. The design approach for a single-polarization and single-mode
PCF has also been discussed. 相似文献
12.
P. Mandelbaum J. L. Schwob 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):173-184
Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization
of ions belonging to the GaI isoelectronic sequence (ground 3d
104s
24p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr5+, Mo11+, Xe23+, Pr28+ and Dy35+. The rate coefficients are given for ions from Kr5+ to U61+ in the GaI sequence at seven electron temperatures (kT
e = 0.1E
I
, 0.3E
I
, 0.5E
I
, 0.7E
I
,E
I
, 2E
I
and 10E
I
, where E
I
is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the
framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along
the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La26+ (Z = 57) at electron temperature of coronal equilibrium maximum abundance. 相似文献
13.
T.-M. Shen C.-Y. Chen Y.-S. Wang Y.-M. Zou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):179-188
A detailed and large-scaled calculation is performed on the total electron impact excitation rate coefficients from the ground
state to the 106 fine-structure levels in 3l-14l′ of Ni-like Gd36+ employing the relativistic configuration-interaction distorted-wave approximation. The resonance contributions from 3l174l′n′′l′′ and 3l175l′n′′l′′ doubly-excited states of Cu-like Gd35+ are taken into account using the isolated process and isolated resonances approximation. The effects of the radiative decays
from the resonances are investigated carefully and are found to be significant. The present rate coefficients, as well as
the collision strength, are compared extensively with the previously published results. We believe our results should be more
accurate and reliable. 相似文献
14.
I. I. Pronin M. V. Gomoyunova D. E. Malygin D. V. Vyalikh Y. S. Dedkov S. L. Molodtsov 《Applied Physics A: Materials Science & Processing》2009,94(3):467-471
The interplay between the phase composition, electronic structure, and magnetic properties of the Fe/Si(100)2×1 interface has been studied at the initial stages of its formation (at Fe doses up to 8 Å). The experiments were carried out in ultra high vacuum by using high-resolution photoelectron spectroscopy with synchrotron radiation. The interface magnetic properties were examined in terms of magnetic linear dichroism in angle-resolved Fe 3p core-level photoemission. It was found that at room temperature a disordered Fe–Si solid solution is formed at the first stage of Fe deposition (≤3.4 Å). In the coverage range of 3.4–4.3 Å the solid solution transforms into Fe3Si. However, the in-plane ferromagnetic ordering of the silicide occurs only at 6.8 Å Fe that demonstrates the thickness dependence of the magnetic properties of Fe3Si. The subsequent sample annealing to 150°C transforms Fe3Si to ε-FeSi, leading to the disappearance of ferromagnetic behavior. 相似文献
15.
L. Láska S. Cavallaro K. Jungwirth J. Krása E. Krousky D. Margarone A. Mezzasalma M. Pfeifer K. Rohlena L. Ry? J. Skála L. Torrisi J. Ullschmied A. Velyhan G. Verona-Rinati 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):487-492
Au ions with maximum charge states 58+ and with the kinetic energy in a region of ∼100 MeV were recorded. The influence of
various experimental conditions is presented and discussed. 相似文献
16.
D. V. Roshchupkin A. I. Erko L. Ortega D. V. Irzhak 《Applied Physics A: Materials Science & Processing》2009,94(3):477-484
X-ray diffraction on a langatate crystal (La3Ga5.5Ta0.5O14, LGT) modulated by a Λ=12 μm Rayleigh surface acoustic wave (SAW) was studied in a double axis X-ray diffractometer scheme at the BESSY synchrotron
radiation source. SAW propagation in the crystal causes sinusoidal modulation of the crystal lattice and the appearance of
diffraction satellites on the rocking curves, with their number, angular positions, and intensities depending on the wavelength
and amplitude of acoustic vibrations of the crystal lattice. Strong absorption of X-ray radiation in LGT enables the observation
of the diffraction spectra extinction at certain SAW amplitudes. X-ray diffraction spectra analysis makes it possible to determine
SAW amplitudes and wavelengths, to measure the power flow angles, and investigate the diffraction divergence in acoustic beam
in LGT. 相似文献
17.
M. Combescot O. Betbeder-Matibet 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):33-46
This paper contains a detailed calculation of the photoinduced current density at third order in the coupling between a semiconductor
and a multifrequency photon field, starting from its standard textbook expression which reads in terms of a triple commutator.
Due to a major intrinsic problem linked to this triple commutator, such a derivation has been made possible quite recently
only, thanks to the tools developed in the composite-boson many-body theory we have recently constructed. The photoinduced
current density is shown to ultimately read in a compact form, in terms of the “Pauli scatterings” and “Coulomb scatterings”
for exciton-exciton interactions introduced in this theory. Representation of this third order response in Shiva diagrams,
which visualize interactions between excitons, is also given to better grasp the physics of the various contributions. 相似文献
18.
M. Tosson O. M. Osman M. M. Osman M. K. Hegab 《Zeitschrift für Physik A Hadrons and Nuclei》1994,347(4):247-253
Intranuclear cascade model calculations are carried out on the recent measurements (WA80 Collaborations) for the multiplicity, energy and angular distributions of singly charged target fragments of energy in the range 30 E < 400=" mev=" (the=" so-called=" grey=" particles)=" produced=" in=" proton-nucleus=" interactions=" at=" 200=" gev/c.=" it=" is=" shown=" that=" these=" distributions=" are=" reasonably=" well=" understood=" in=" terms=" of=" the=" intranuclear=" cascade=" model=" which=" considers=" that=" grey=" particles=" are=" only=" produced=" in=" the=" first=" two=" generations=" of=" the=" cascade.=" the=" obtained=" distributions,=" mean=" values=" and=" target=" mass=" dependence=" are=" more=" consistent=" with=" the=" experimental=" data=" than=" other=" models=" using=" monte=" carlo="> 相似文献
19.
A. Yu. Elizarov I. I. Tupitsyn 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):67-74
The plane wave Born approximation is used to calculate total
electron impact ionization cross section of silver and copper.
Wavefunctions of the target and residual ions were modeled by non orthogonal
Hartree-Fock and Dirac-Fock orbitals. The wave
functions of the atom and residual ion
are calculated with allowance for relaxation effects.
The one-electron wavefunction of the continuous spectrum for the ejected
electron is obtained using single-configuration Hartree-Fock and
Dirac-Fock method. The orthogonalization of the ejected electron wave
functions to all occupied orbitals of the target atom is performed.
Results of calculations are compared to available experimental measurements
and theoretical calculations performed by non relativistic one-electron
PWBA, where the ejected electrons is modeled by the hydrogenic Coulomb
wave function. 相似文献
20.
Summary The diffraction of a spherical acoustic wave from the juncture of pressure release (soft) and locally reacting (absorbing)
half-planes in a fluid moving at subsonic velocity is examined. This consideration is important because the point sources
are regarded as better substitutes for real sources than line sources/plane waves. The integral representation of the field
is obtained using integral transforms and the Wiener-Hopf technique. The factorization of the kernel function in the Wiener-Hopf
functional equation is accomplished. The analytic solution of the integrals is obtained by employing asymptotic methods and
the far field is presented. The effect of the Mach number is shown explicitly on the diffracted field. 相似文献