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Wyświetlanie 1-15 z 43
Tytuł:
A simple and practical color image encryption with the help of QR code
Autorzy:
Deng, X
Zhu, X.
Powiązania:
https://bibliotekanauki.pl/articles/173289.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
color image encryption
quick response (QR) code
joint transform correlator (JTC)
Opis:
A simple and practical color image encryption is proposed with the help of quick response (QR) code. The original color image to be encoded is firstly transformed into the corresponding QR code, and then a joint transform correlator encrypting architecture is used to encode the corresponding QR code into a positive ciphertext. In the decryption, the corresponding QR code can be restored with the correct decryption key, and hence the original color image can be retrieved without any quality loss by scanning the restored QR code with a smartphone. Compared with the reported color image encryption techniques, the proposed technique does not need to convert color image (RGB) into indexed image formats or segregate into three color components prior to encryption and hence the corresponding reverse processes also are not required after decryption. Moreover, with the help of the QR code, the proposed method has strong tolerance to speckle noise and other noises resulting from optical system. In addition, the proposed method is practical because its ciphertext is a positive image and can be printed directly or manufactured as a card. The feasibility and effectiveness of the proposed method are demonstrated by numerical results.
Źródło:
Optica Applicata; 2015, 45, 4; 513-521
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tight focusing of radially polarized beams by a devil’s vortex lens
Autorzy:
Chen, Z.
Hu, X.
Chen, X.
Wang, X.
Pu, J.
Powiązania:
https://bibliotekanauki.pl/articles/173576.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
devil’s vortex lens
radially polarized beam
tight focusing
high numerical aperture
Opis:
Tight focusing of radially polarized beams with a devil’s vortex lens is numerically investigated. Multiple focal spots can be generated in the geometric focus when a radially polarized beam is focused by a high numerical aperture objective in the presence of a devil’s vortex lens. The position of the major focal spot shifts from the geometric focus when a devil’s vortex lens with S = 1 is employed, and the position of the focal spot can be controlled by the numerical aperture of the objective. The intensity components of the major focal spot are influenced by the vortex phase of the devil’s vortex lens. A strong longitudinal component near the optical axis is produced by a devil’s vortex lens without vortex phase, and a nearly pure transversal field is produced by a devil’s vortex lens with vortex phase.
Źródło:
Optica Applicata; 2018, 48, 3; 389-398
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of circular aperture diffraction on propagation properties of cylindrical vector partially coherent Laguerre–Gaussian beams in turbulent atmosphere
Autorzy:
Peng, Z.
Jia, X.
Powiązania:
https://bibliotekanauki.pl/articles/173537.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
cylindrical vector beams
diffraction
aperture
atmospheric propagation
Opis:
On the basis of the extended Huygens–Fresnel integral formula, the analytical formulae for the cross-spectral density matrix of the arbitrary cylindrical vector partially coherent Laguerre–Gaussian beams diffracted by a circular aperture in turbulent atmosphere are derived. The average intensity, the degree of polarization, and the degree of coherence of the apertured cylindrical vector partially coherent beams propagating in turbulent atmosphere are investigated. The analyses indicate that both the beam diffraction effect by a circular aperture and the atmospheric turbulence have a great impact on the beam evolution, polarization and coherence properties of the apertured cylindrical vector partially coherent beams.
Źródło:
Optica Applicata; 2018, 48, 3; 421-433
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of inner and outer scale on beam spreading for a Gaussian wave propagating through anisotropic non-Kolmogorov turbulence
Autorzy:
Gao, C.
Li, X.
Powiązania:
https://bibliotekanauki.pl/articles/174609.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
anisotropy
Gaussian wave
long-term spreading radius
non-Kolmogorov turbulence
inner scales of turbulence
outer scales of turbulence
Opis:
Experimental results and empirical research have shown that atmospheric turbulence can present the anisotropic property not only at a few meters above the ground but also at high altitudes of up to several kilometers. This paper investigates beam spreading for a Gaussian wave propagating along a horizontal path in weak anisotropic non-Kolmogorov turbulence. Mathematical expressions for the long-term beam spreading radius were obtained based on the generalized von Kármán spectrum for anisotropic turbulence. The final model includes an anisotropic factor, which parameterizes the asymmetry of a turbulence cell, the spectral power law for non-Kolmogorov turbulence, the inner and outer scale of turbulence, and other essential optical parameters of a Gaussian wave. Numerical simulations indicate that the long-term beam spreading radius decreases with an increase in the anisotropic factor. We also analyze how the geometrical optics approximation may cause large errors for a small spectral power law value.
Źródło:
Optica Applicata; 2017, 47, 1; 63-74
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fast near-infrared palmprint recognition using nonnegative matrix factorization extreme learning machine
Autorzy:
Xu, X.
Zhang, X.
Lu, L.
Deng, W.
Zuo, K
Powiązania:
https://bibliotekanauki.pl/articles/173572.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
extreme learning machine
palmprint recognition
superior speed
support vector machine (SVM)
Opis:
Support vector machine and artificial neural network are widely used in classification applications. Extreme learning machine (ELM) is a novel and efficient learning algorithm based on the generalized single hidden layer feed forward networks, which performs well in classification applications. The research results have shown the superiority of ELM with the existing classical algorithms: support vector machine (SVM) and back propagation neural network. In this study, we firstly propose a novel nonnegative matrix factorization extreme learning machine (NMFELM) to improve the performance of standard ELM method. Then we propose a novel near-infrared palmprint recognition approach based on NMFELM classifier. As the test data, we use the near-infrared palmprint database provided by Hong Kong Polytechnic University. The experimental results demonstrate that the proposed NMFELM method outperforms the standard ELM- and SVM-based methods.
Źródło:
Optica Applicata; 2014, 44, 2; 285-298
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evolution properties of multi-Gaussian Schell model beams propagating in uniaxial crystal orthogonal to the optical axis
Autorzy:
Lu, X.
Shen, Y.
Zhu, X.
Zhao, C.
Cai, Y.
Powiązania:
https://bibliotekanauki.pl/articles/173654.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
propagation properties
partially coherent
uniaxial crystal
Opis:
An analytical formula for the multi-Gaussian Schell model is derived for the beam propagating in a uniaxial crystal orthogonal to the optical axis. The propagation properties of multi-Gaussian Schell model beams in a uniaxial crystal orthogonal to the optical axis is investigated by using the analytical formula. Some results are illustrated by numerical examples related to the propagation properties of multi-Gaussian Schell model beams. It is found that the propagation properties of the multi-Gaussian Schell model beams are very different from the propagation properties in the free space. They are closely related to the initial coherence and the ratio of the extraordinary and ordinary refractive indices. The results provide a way for studying the propagation properties of the multi-Gaussian Schell model beams in the uniaxial crystal orthogonal to the optical axis.
Źródło:
Optica Applicata; 2016, 46, 1; 19-34
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrashort pulse propagation recording by using the transmission-type light in flight holography
Autorzy:
Fan, Y.
Li, J.
Zheng, S.
Lu, X.
Zhong, X.
Powiązania:
https://bibliotekanauki.pl/articles/174016.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
light in flight
visualization of pulse propagation
holography
Opis:
In this paper, the distortion of the reconstructed images of the propagating light pulse in transmission light-in-flight holography recording was analyzed. Based on the analysis model, for recording the wavefront more accurately, the optimized selection of relevant parameters was made. Furthermore, a cylindrical lens was introduced to correct the image distortion. Additionally, the light-in-flight recording of the wavefront changing during propagation was simulated.
Źródło:
Optica Applicata; 2017, 47, 2; 283-294
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
SO(3) matrix transformation for rapid polarization search and coding in a three-plate polarizer
Autorzy:
Huang, C
Wang, X
Powiązania:
https://bibliotekanauki.pl/articles/174349.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
SO(3) transformer
tabu search
polarization coding
Opis:
A SO(3) transformer of a three-plate polarizer is adopted to rapidly achieve the transformation of the polarized state. The polarization coding based on Stokes components S2 and S3 is analyzed and demonstrated. Tabu search algorithm is used to accelerate the transformation of the polarized state by utilizing Mueller matrix roots decomposition to decompose the SO(3) matrix, and substituting first order Taylor series approximations for the trigonometric functions in the SO(3) matrix. The results show that bias voltage is less than 120 V in the coding zone. The search speed of our algorithm is faster than the one without first order Taylor series approximations by 4 times.
Źródło:
Optica Applicata; 2015, 45, 1; 101-112
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical gradient force of cosh-Gaussian with sine-azimuthal and half-space phase modulation
Autorzy:
Fu, R.
Gao, X.
Shen, H.
Xin, Q
Lu, X.
Guo, L.
Powiązania:
https://bibliotekanauki.pl/articles/173789.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
optical gradient force
cosh-Gaussian beams
wavefront modulation
Opis:
The optical gradient force distributions in focal plane of cosh-Gaussian beams with sine-azimuthal variation wavefront and half space phase modulation were investigated. Results show that optical gradient force distributions can be affected considerably by the phase retardation of half-space phase modulation, of a phase parameter that indicates the phase change frequency on an increasing azimuthal angle, and beam parameters in cosh terms of the incident beams. Many gradient force patterns occur, including cross-shape, multiple optical trap arrays, multiple-trap wheel, and many kinds of gradient force lines and curves. Symmetry of the whole gradient force pattern can also be altered remarkably. Above results may find wide applications in optical trapping systems.
Źródło:
Optica Applicata; 2013, 43, 4; 719-730
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fiber-optic accelerometer based on a modal interferometer using a thin-core fiber
Autorzy:
Wang, X
Wu, X
Li, S
Ge, Q
He, T
Yu, B
Powiązania:
https://bibliotekanauki.pl/articles/174927.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
fiber-optic accelerometer
modal interferometer
thin-core fiber
Opis:
A compact fiber-optic accelerometer based on a modal interferometer, which is fabricated by misaligned splicing of a short section of a thin-core fiber between two sections of a standard single-mode fiber, is demonstrated experimentally. A spectrum analysis method is used to detect an acceleration signal rapidly. The experimental results show that the thin-core fiber-based fiber-optic accelerometer has a minimum detectable acceleration of 3.3×10–3g (g – gravitational acceleration), and a wide frequency response range from 10 to 1200 Hz. Moreover, the proposed accelerometer exhibits the advantages of low cost, simple structure and easy fabrication.
Źródło:
Optica Applicata; 2015, 45, 3; 317-325
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Method for improving sinusoidal quality of error diffusion binary encoded fringe used in phase measurement profilometry
Autorzy:
Tian, Z.
Chen, W.
Su, X.
Powiązania:
https://bibliotekanauki.pl/articles/174421.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
phase measurement profilometry
digital-light-processing projector
DLP projector
error diffusion algorithm
binary encoded grating
Opis:
Insufficient resolution of digital-light-processing projector will degrade the sinusoidal quality of the binary encoded fringe pattern because of less sampling points in a fringe period, which will degrade the measurement accuracy if it is used in phase measurement profilometry. Two resolutions are proposed in the paper. One is that a cylindrical lens is introduced in the projecting light path of the measurement system to improve sinusoidal quality of the binary encoded fringe by elliptical low-pass filtering of the system. The other one is that superposition of multi-frame binary encoded gratings with different microstructure is to reduce the binary image noise for improving the measurement accuracy. Simulations and experiments verify the validity of the above two methods.
Źródło:
Optica Applicata; 2016, 46, 2; 291-303
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Focus shaping of Weierstrass solid immersion lens by an axisymmetric Bessel-modulated Gaussian beam
Autorzy:
Dong, X
Geng, T
Zhuang, S
Powiązania:
https://bibliotekanauki.pl/articles/174767.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Weierstrass solid immersion lens
Bessel-modulated Gaussian beam
vector diffraction theory
Opis:
Weierstrass solid immersion lens (SIL) has been used to obtain superresolution because a smaller focal size is desirable. In this paper, focus shaping of Weierstrass SIL illuminated by an axisymmetric Bessel-modulated Gaussian beam (QBG beam) is investigated. It has been found theoretically that the sharper focusing of Weierstrass SIL disappears for a certain beam order of QBG beam. For case of a smaller beam order, the focus still locates on the plane of Weierstrass SIL and Weierstrass SIL still plays a tighter focusing role. However, when the beam order increases continuously, the focus lefts the plane of Weierstrass SIL, and shifts along an optical axis considerably. In addition, under condition of the higher beam order, the dependence of the focal shift on the beam order is nearly linear, which may be used to alter a focal position conveniently.
Źródło:
Optica Applicata; 2013, 43, 2; s. 247-259
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Colloidal crystal cladded microfiber for refractive index sensing
Autorzy:
Yan, H. T.
Zhao, X Y
Zhang, Ch.
Zhen, Z Q
Li, Q Z
Cao, J X
Xia, L X
Powiązania:
https://bibliotekanauki.pl/articles/174902.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
microfibers
colloidal crystals
refractive index sensing
Opis:
We investigate the evanescent field of a microfiber wrapped by colloidal crystals. The microfiber has the diameter of about 1 μm that is drawn from a single-mode fiber with an alcohol lamp. The colloidal spheres are further attached to the microfiber through thermal evaporation, then they self-assemble to crystal-like structures. The 400 nm, 590 nm, and 710 nm-diameter SiO2 colloidal spheres are used, respectively. The spectral responses are studied theoretically and experimentally, and the results agree with each other. It is revealed that the evanescent field of a microfiber could be modulated by the photonic band-gap of colloidal crystals. This characteristic is very useful in refractive index sensing for liquids.
Źródło:
Optica Applicata; 2014, 44, 2; 309-315
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Real-time optical demultiplexing with the chirped pulses
Autorzy:
Li, Y.
Zhang, X.
Yuan, J.
Kang, Z.
Sang, X.
Kang, S.
Kang, X.
Yan, B.
Wang, K.
Yu, C.
Powiązania:
https://bibliotekanauki.pl/articles/175106.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
linearly chirped pulse
parametric process
real-time optical demultiplexing
Opis:
A scheme for real-time optical demultiplexing is proposed by utilizing the time-broadened and linearly chirped pulses instead of the conventional mode-locked pulses. The copies of the optical-time-division-multiplexed signal are acquired through a dual-pump parametric gate and used as the parametric multicast block. Simulation results show that the demultiplexing from 160 Gb/s down to sixteen 10 Gb/s tributaries can be achieved only by using a sampling source of 10 GHz. The proposed scheme can effectively reduce the complexity of parallel processing, and find important applications in the high-speed all-optical signal processing.
Źródło:
Optica Applicata; 2018, 48, 4; 621-632
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design of LED collimator for uniform illumination using two freeform lenses
Autorzy:
Zeng, J.
Li, X.
Ge, P.
Powiązania:
https://bibliotekanauki.pl/articles/173429.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
illumination design
lenses
light-emitting diodes
optical design
high uniformity
Opis:
Regulating the illuminance distribution of an LED collimator to produce a uniform illumination in both the near field and the far field is a challenge in illumination design. In this paper, we present an effective method for designing two separated freeform lenses to control the illuminance distribution and the direction of the rays from the LED. The first lens redistributes the ray energy, and the second one collimates them to obtain a uniform collimated illumination. According to the conservation law of energy, Snell’s law, Fermat’s law and tangent-plane iterative method, the two freeform surfaces could be calculated simultaneously. The simulation results show that the two freeform lenses can control most of rays into an angle within ±1.5° for an LED with 1 × 1 mm size. The illuminance uniformities are higher than 0.9 in both the near field and the far field.
Źródło:
Optica Applicata; 2018, 48, 3; 413-420
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 43

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