Journals >Acta Photonica Sinica
Contents
2013
Volume: 42 Issue 4
24 Article(s)
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Research Article
Flat Spectral Response of Arrayed Waveguide Grating
ZHANG Li-yao, WU Yuan-da, AN Jun-ming, WANG Yue, WANG Liang-liang, PAN Pan, ZHANG Jia-shun, ZHANG Xiao-guang, and HU Xiong-wei
It is significant of the flat spectral response arrayed waveguide grating in practical application. Flat spectral response arrayed waveguide grating is systematically studied. Tapers with exponential type are introduced into input waveguides, output waveguides and arrayed waveguides. Optimal design is achieved by changIt is significant of the flat spectral response arrayed waveguide grating in practical application. Flat spectral response arrayed waveguide grating is systematically studied. Tapers with exponential type are introduced into input waveguides, output waveguides and arrayed waveguides. Optimal design is achieved by changing the shape and size of the tapers. Firstly, the output spectral characteristic is discussed theoretically for tapers with exponential type and the relational expressions of the structural parameters are given. It is illustrated that the characteristic of the tapered input waveguides is the main factor that affects the output spectrum and that the tapered arrayed waveguides and the tapered output waveguides have a certain impact on the output spectrum. Secondly, numerical simulation method is used to simulate the output spectrum and to optimize the structure. Trend and regularity about flat spectral response affected by the structure of tapers are concluded. Simulation results show that the 1 dB passband width is bigger than 50% of the channel spacing, Insertion loss decreases from 5.2 to 4.0 dB, crosstalk is less than -30 dB. Finally, the experimental results are given, insertion loss reduces 0.87 dB, crosstalk decreases 3.67 dB, and 1 dB bandwidth increases 0.1 nm with an increase of 54.7%. Experimental results show that the introduction of tapered waveguides with the exponential type improves the spectral properties of the arrayed waveguide grating device..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 379 (2013)
Optical Propagation and Interference in the Sub-wavelength Metallic Waveguide
TANG Wei-min, WANG Zheng-ling, and JIANG Wen-fan
Properties of optical propagation as well as interference in the sub-wavelength metallic waveguide based on the extraordinary transmission are investigated by the Finite Difference Time Domain(FDTD) method. And several parameters on the standing wave as well as the coupling of two standing waves are studied, which is uProperties of optical propagation as well as interference in the sub-wavelength metallic waveguide based on the extraordinary transmission are investigated by the Finite Difference Time Domain(FDTD) method. And several parameters on the standing wave as well as the coupling of two standing waves are studied, which is useful to understand the properties of optical propagation and the extraordinary transmission in the sub-wavelength metallic waveguide. It shows that TE light field is hard to propagate efficiently in the sub-wavelength metallic waveguide as the waveguide width is much smaller than the half wavelength. The propagating distance of the TE light field will be larger with the increasing of the waveguide width and can propagate generally when the waveguide width is about or larger than the half wavelength. There is a cut-off wavelength in the waveguide and it is linearly proportional to the absorption coefficient of the metal. In addition, due to the extraordinary transmission, it generates the standing wave in the sub-wavelength metallic waveguide..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 386 (2013)
Raman Spectra Study of Thermal Effect of Polymer Light-Emitting Diodes
QIN Zhe, WANG Jian, and ZHANG Cun-zhou
Raman spectra and infrared imaging systems are used for the study of internal temperatures of polymer light-emitting diodes. The thermal degradations of polymer light-emitting diodes with different current densities are investigated. Raman intensity is proportional to the number of molecules in the next higher vibratioRaman spectra and infrared imaging systems are used for the study of internal temperatures of polymer light-emitting diodes. The thermal degradations of polymer light-emitting diodes with different current densities are investigated. Raman intensity is proportional to the number of molecules in the next higher vibration energy level, and accurate internal temperature of polymer light-emitting diodes at thermal equilibrium can be calculated with the ratio of anti-stokes to stokes Raman intensity by Boltzmann equation. With the current density of polymer light-emitting diodes going from 0 to 169 mA/cm2, it is found that the internal temperature of polymer light-emitting diodes increases accordingly. When the temperature comes to the glass transition temperature of the emission layer, there is a phase change in it and the layer becomes free state as liquid, which is not stable. Local disfigurement in the emission layer results in short circuit between the cathode and the anode of a polymer light-emitting diode, and the luminescence of polymer light-emitting diode fails. Therefore, Raman spectra is considered as a good method for detecting temperature of thin-film semiconductor devices..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 392 (2013)
Simultaneous Measurement of Piezoelectric and Electro-optical Coefficients of Crystal Material Utilizing Ultrahigh Modes
XIAO Ping-ping, and DENG Man-lan
A novel method for simultaneous measuring piezoelectric coefficient and electro-optical coefficients of crystal material is proposed by utilizing the ultrahigh modes excitation from a symmetrical metal-cladding optical waveguide. The method can be directly used to calculate the electro-optic coefficient and piezoelectrA novel method for simultaneous measuring piezoelectric coefficient and electro-optical coefficients of crystal material is proposed by utilizing the ultrahigh modes excitation from a symmetrical metal-cladding optical waveguide. The method can be directly used to calculate the electro-optic coefficient and piezoelectric coefficient by shift of the reflectance curves at different voltages. The theoretics and experiment results all indicate that this method has an excellent performance, such as high compact, low insert loss, no moving parts, high reliability and so on, which promises an application prospect in optical devices in electro-optic coefficient and piezoelectric coefficient..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 397 (2013)
Fabrication of 1×4 Optical Waveguide Splitter by Femtosecond Laser in LiNbO3
ZHOU Zi-gang, LUO Chen, YANG Yong-jia, FAN Zong-xue, QUAN En-si, ZHU Wan-qing, and WANG Liang
This paper reports the experimental research of optical channel waveguides in Z-LiNbO3 crystals by femtosecond pulses. The laser scanning trajectory is controlled by the five power function program. A 1×4 optical splitter was prepared by the horizontal scanning when the pulse energy is 270 mW, the scanning speed fThis paper reports the experimental research of optical channel waveguides in Z-LiNbO3 crystals by femtosecond pulses. The laser scanning trajectory is controlled by the five power function program. A 1×4 optical splitter was prepared by the horizontal scanning when the pulse energy is 270 mW, the scanning speed from 50 μm to 200 μm per second. The result shows that the scanning speed is slower, and the repeat times are more, the waveguide width is wider..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 402 (2013)
Design and Characteristics of a Broad-band Metamaterial Absorber
SHI Xiao-qiang, GONG Qiao-xia, DUAN Zhi-yong, MA Feng-ying, and ZHU Zhi-xian
To obtain the high absorptivity and broad bandwidth, a resonant metamaterial absorber composed of split rings is designed and investigated numerically by employing the frequency domain solver of the commercial software (CST Studio Suite 2009). The calculated absorption spectrum in 25~35 GHz range shows that a very highTo obtain the high absorptivity and broad bandwidth, a resonant metamaterial absorber composed of split rings is designed and investigated numerically by employing the frequency domain solver of the commercial software (CST Studio Suite 2009). The calculated absorption spectrum in 25~35 GHz range shows that a very high absorption of 86%with a broad bandwidth of 3.5 GHz can be achieved. Moreover, its absorbing performances in THz frequency are investigated. The complex absorbing structure by combining the elementary absorber based on the superposition effect of absorption at different frequencies is also discussed.It is shown that the complex metamaterial absorber can reach a nearly perfect absorption of 99.9%,with the bandwidth of 3.1 GHz. To minify 1 000 times of the absorber size in GHz frequency, the perfect absorber can be achieved in the THz frequency, thus providing a means to dynamically control the absorbing band. Obviously, the absorption is increased largely when compared to that of the elementary absorbers. Meanwhile, different simulation results of diverse arrays can be calculated. Due to the interaction of the ring resonators, the absorption effect can be influenced and absorption rate decreased. This metamaterial consists entirely of metal structure which allows for maximization of the absorption through independent controlling the electrical permittivity and magnetic permeability..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 405 (2013)
Influence of Surface ZnO Nano-structures on the Light Emitting Efficiency of GaN-based LED
LI Wei, YUE Qing-yang, KONG Fan-min, and LI Kang
In order to improve the light emitting efficiency(LEE) of GaN-based blue LED, two LED models covered by ZnO nano-structures, including nano-rod and nano-cone structures, are simulated in the method of FDTD. The results of these simulations show that the light emitting efficiency of LED is varying regularly with the difIn order to improve the light emitting efficiency(LEE) of GaN-based blue LED, two LED models covered by ZnO nano-structures, including nano-rod and nano-cone structures, are simulated in the method of FDTD. The results of these simulations show that the light emitting efficiency of LED is varying regularly with the different nanostructures’geometric parameters (such as the period: P, the wide of bottom: W, and the length: L). The optimized model structure is obtained, and it is found that both ZnO nano-rod and nano-cone can bring obviously incensement (250% and 230%) on LEE. Besides, with the analysis on the variation curve, the influence of ZnO nano-structure and the reason of the optimization results are theoretically explained. These results provide a theoretical reference on the practical design and optimization of highly efficient GaN-based LED..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 409 (2013)
Uniform Removal of the Surface Material of the Optical Components in Ultra-smooth Technology
CHEN Hua-nan, WANG Jun-lin, and LIU Jian
Accuracy of the intermediate frequency and the high frequency, of the optical components, are enhanced during the ultra-smooth processing, under the premise of non-deterioration of its surface accuracy. The uniform removal is an important way to ensure of non-degradation of the surface accuracy of the optical componentAccuracy of the intermediate frequency and the high frequency, of the optical components, are enhanced during the ultra-smooth processing, under the premise of non-deterioration of its surface accuracy. The uniform removal is an important way to ensure of non-degradation of the surface accuracy of the optical components during the ultra-smooth processing. On the basis of the four-axis three linkage machine with small grinding heads, used for ultra-smooth processing , combined with the Preston hypothesis, the characteristics of the material removal of the optical components are studied. When the machine takes some specific parameters, uniform removal of the surface material of the optical element can be achieved with equivalent dwell time. Finally, comparison tests are done to test the specific parameters. The test results confirm the results of the theoretical analysis..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 417 (2013)
A Kind of S-type Structure of Left-handed Materials for 60 GHz Communication
ZHOU Fu-kun, YI Qiang, and LUO Xing-fang
The S-typed LHM is selected as design objective. The center frequency of S-typed structure is set as 60 GHz. By reasonably varing the corresponding parameters size of unit structure, the required electric resonance and magnetic resonance frequency can be obtained. Based on the theoretical analysis of S-typed structure,The S-typed LHM is selected as design objective. The center frequency of S-typed structure is set as 60 GHz. By reasonably varing the corresponding parameters size of unit structure, the required electric resonance and magnetic resonance frequency can be obtained. Based on the theoretical analysis of S-typed structure, the coincidence frequency of negative permeability and permittivity can be optimized as possible as ideal. The dielectric constant of substrate can effect the characteristic and stability of LHM. In this paper, the dielectric constant is set as 2.2. The electromagnetic parameters are extracted using NRW method. The negative ε and negative μ index can be obtained in the band from 58.1 GHz to 61.4 GHz which is proved as left-hand band. From the simulation results of scattering parameters, it can be observed that the S21 values are greater than -3 dB with the frequency range from 58 GHz to 62 GHz and the S11 values are less than -20 dB with the frequency range of 59.8~60.4 GHz. Therefore, the results can be referred as the design of filter and antenna for 60 GHz communication..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 423 (2013)
Failure Prediction of Coiled Fibers
LIANG Xiao-hong, and LIU Jun-hao
The mechanism of crack occurrence and propagation in optical fibers were reviewed with emphasis on the reliability of optical fibers. The lifetime prediction model of communication optical fibers were given on the basis of the fracture mechanics. The stresses distribution of optical fibers in the configuration of fiberThe mechanism of crack occurrence and propagation in optical fibers were reviewed with emphasis on the reliability of optical fibers. The lifetime prediction model of communication optical fibers were given on the basis of the fracture mechanics. The stresses distribution of optical fibers in the configuration of fiber coils was analyzed. A general model was derived for evaluating the mechanical reliability of this kind of coiled sensing fibers. The model was then simplified to an alternative model for engineering applications. This simplified model would bring the conserved results out rapidly and simply. Several numerical calculations of the failure probability in service time of various fiber coils with different fiber radius and bending radius were carried out using the simplified model. The results displayed the dependence of the failure probability on the parameters of the fibers, coils, and the process. According to the relation, the failure probability and the lifetimes could be estimated for fiber coils installed. Meanwhile, the relations provided the guidelines to various design solutions of the fiber coils with deferent geometric configurations and service conditions in the future..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 427 (2013)
Detection of Underwater Low-frequency Acoustic Signal and Wave Attenuation
MIAO Run-cai, WANG Yu-ming, MENG Feng, and MA Jing
A simple measurement system is developed to study the optical effect of the low-frequency liquid surface wave which excited by underwater acoustic source. The high stability and clear diffraction pattern was observed experimentally.The relationship between diffraction patterns divergence angle and the distance of the aA simple measurement system is developed to study the optical effect of the low-frequency liquid surface wave which excited by underwater acoustic source. The high stability and clear diffraction pattern was observed experimentally.The relationship between diffraction patterns divergence angle and the distance of the acoustic signal was derived. Furthermore, with the increase of distance, the diffraction patterns divergence angle will decrease. The damping characters of the liquid surface wave was theoretically obtained when underwater acoustic wave spread to the liquid surface.The analytical expression between diffraction patterns divergence angle and the liquid surface wave amplitude was theoretically derived. It was found that the surface wave amplitude is exponent attenuation with the change of the horizontal distance.The attenuation coefficients is dependent on the frequency of liquid surface acoustic wave, and the greater frequency, the smaller attenuation coefficient..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 432 (2013)
Analytical Solution and Spatiotemporal Coupling Effect for Ultra-short Pulsed Radially Polarized Beams
LU Da-quan
Based on the propagation equation which governs the propagation of ultra-short pulsed beams, and by utilizing the Fourier transform technique as well as the commutation relation between two mathematical operators, the analytical solution for ultra-short pulsed radially polarized beams is obtained. This solution is applBased on the propagation equation which governs the propagation of ultra-short pulsed beams, and by utilizing the Fourier transform technique as well as the commutation relation between two mathematical operators, the analytical solution for ultra-short pulsed radially polarized beams is obtained. This solution is applicable to radially polarized beams driven by any pulse. On the basis of the solution, the propagation properties of the ultra-short pulsed radially polarized beams are discussed. It shows that the pulse at the beam periphery is delayed compares to that around the beam center. This effect results in the the varying of transverse intensity distribution of the ultra-short pulsed radially polarized beam at different temporal positions during propagation, and the asymmetric intensity distribution of the vertical profle at the head and the trail of the pulse. The method used in this paper is applicable in obtaining the analytical solution and the propagation properties for the ultra-short pulsed azimuthally polarized beams..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 437 (2013)
Superresolution Technology of Gaussian Beam under High Numerical Aperture
WANG Wei
Using vector diffraction theory, the superresolution properties of Gaussian beam are studied under high numerical aperture. The two and three rings phase structures, which can realize superresolution, are solved and optimized. The varirty regularities of superresolution properities are analyzed with the changing of radUsing vector diffraction theory, the superresolution properties of Gaussian beam are studied under high numerical aperture. The two and three rings phase structures, which can realize superresolution, are solved and optimized. The varirty regularities of superresolution properities are analyzed with the changing of radius and phase. The methods and solutions of optimization are also given. The results show that superresolution can be get with the same side lobe at illumination of plane wave, when using the Gaussion beam illumination.The inner radius is crucial when using two ring phase structure and the property of superresolution has little change with tiny phase changing. Two ring phase structures have the advantages of machining tolerances. Three ring phase structures can get larger compression radio and small peak intensity of the main lobe with the same side lobe. The changing of radius and phase has important influence on the performance of superresolution. The machining tolerance is smaller than that of two ring phase structure. For both two and three ring phase structure, the increase of compression radio will inevitably cause the decrease of main lobe peak intensity and the increasing of the sidelobe radio. This research provides a new method for the design of superresolution pupil filter with Gaussian beam illumination under high numerical aperture..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 441 (2013)
Demodulation of Part Period Signal of Fourier Telescope and Effects for Imaging
DONG Lei, LIU Xin-yue, LIU Jie, and YU Shu-hai
In order to settle the problem of high power short pulse laser of Fourier telescope including part period of signal, the technique of multiple pulse segment was first put forward and its basic principle and application was also first studied. Firstly, the conflict between high power short pulse laser and band width of In order to settle the problem of high power short pulse laser of Fourier telescope including part period of signal, the technique of multiple pulse segment was first put forward and its basic principle and application was also first studied. Firstly, the conflict between high power short pulse laser and band width of acousto-optic frequency shifter was introduced, and then the difficulty that part period signal was demodulated by conventional time demodulation formula of Fourier telescope was put forward. Secondly, the basic principle of multiple pulse segment was given and the condition of segment between shifting frequency, pulse repetition and pulse width under ideal instance was deduced. Thirdly, the effects of stabilization of frequency shifting and pulse repetition on imaging results of multiple pulse segment were analyzed and the effects of changing pulse width on imaging results of multiple pulse segment under usual condition were studied by computer simulation. At last, the conclusion was acquired that shifting frequency and pulse repetition had no effects on imaging and the figure of object could also been identified under the condition of laser pulse changing less than 25%..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 447 (2013)
Influence of Inhomogeneity of Optical Glass Used in High-precision Optical System on Imaging Quality
LIU Yang-zhou, LI Xiao-tong, CEN Zhao-feng, XU Wei-cai, SHANG Hong-bo, and RUAN Wang-chao
Inhomogeneity of optical glass used in high-precision optical system influences the imaging quality of the system. This kind of inhomogeneity can be expressed by Zernike polynomial expression with the discrete refractive-index data measured by ZYGO interferometer, in order to use the Fourth Order Runge-Kutta method forInhomogeneity of optical glass used in high-precision optical system influences the imaging quality of the system. This kind of inhomogeneity can be expressed by Zernike polynomial expression with the discrete refractive-index data measured by ZYGO interferometer, in order to use the Fourth Order Runge-Kutta method for ray tracing. Due to the randomness of the material′s refractive-index distribution, using different part of one piece of semi-finished optical glass to manufacture lenses with same parameter and rotating manufactured lens different degrees around the optical axis would influence the optical system′s performance..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 451 (2013)
Development of Spaceborne Wide-angle Aerosol Imager with Low-distortion and Uniform Image Surface
XUE Qing-sheng, WANG Shu-rong, and CHEN Wei
In order to meet the urgent requirements of space remote sensing, a spaceborne wide-angle aerosol imager prototype with low-distortion and uniform image surface is designed. The illuminance distribution on image plane is improved by using effective aberration vignetting resulted from stop aberration, and the problem ofIn order to meet the urgent requirements of space remote sensing, a spaceborne wide-angle aerosol imager prototype with low-distortion and uniform image surface is designed. The illuminance distribution on image plane is improved by using effective aberration vignetting resulted from stop aberration, and the problem of non-uniform illuminance on the image plane of wide-angle optical system. The distortion is corrected by choosing appropriate optical structure. The optical elements are all spherical face, so it is easy to fabricate and test. The central wavelength is 670 nm, wavelength band is 20 nm, and full field of view is 72°, the relative aperture is 1∶3.6, and the focal length is 20 mm. Experiments show that the entrance pupil size is 5.6 mm, the relative illuminance of edge field of view is 95.6%, the MTF of on-axis FOV is more than 0.61@36 lp/mm, the MTF of off-axis FOV is more than 0.58@36 lp/mm, and the maximum distortion is -1.95%, , which satisfies the pre-designed requirement. Its structure is compact, and feasible for applying in space remote sensing..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 456 (2013)
Athermal Design for IR Optical Seeker System with Wide FOV
Jiang Yang, Sun Qiang, Liu Ying, and Zhao Longxian
In order to stabilize the optical performance influenced by the temperature changes, an optical seeker with conformal dome on the basis of the passive optical athermallization method is discussed. Reasonable materials are chosen correctly according to athermal equations. The hybrid refractive-diffractive configuration In order to stabilize the optical performance influenced by the temperature changes, an optical seeker with conformal dome on the basis of the passive optical athermallization method is discussed. Reasonable materials are chosen correctly according to athermal equations. The hybrid refractive-diffractive configuration is introduced for the design of athermal optical system design.Ellipsoidal conformal dome could optimize the aerodynamic performance and reduce the heating of the missile dome.missile dome heating. Inverted telephoto triplet is helpful to acquire short focal length and wide FOV. It is shown that an optical system with ±90° unvignetted FOR, F/2, 100% cold stop efficiency was present. A back focal length of 22.8 mm is large enough for the cooled detector, and also MTF are higher than 0.4 at the spatial frequency of 15 lp/mm across the entire field with the working wavelength at 3~5 μm. The specifications can satisfy the requirements of precise seeker, which can ensure the compact design of the system..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 462 (2013)
Design of an Optical Integrator for Solar Simulator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Aiming at lower irradiation uniformity of the traditional solar simulator, an optical integrator is designed which can effectively improve the irradiation uniformity of sun simulator. The composition and working principle of optical integrator is introduced, optical optimization design technology of optical integrator Aiming at lower irradiation uniformity of the traditional solar simulator, an optical integrator is designed which can effectively improve the irradiation uniformity of sun simulator. The composition and working principle of optical integrator is introduced, optical optimization design technology of optical integrator is described, optical and mechanical structure of the optical integrator is designed reasonably, and the ansys software is used for thermal analysis of the machine structure. Finally, lightTools software is used to be simulating for solar simulator. The results show that: after using the optical integrator, irradiation non uniformity of the sun simulator is markedly improved, irradiation non uniformity in 60 mm range is less than ±1%, and in (60~200) mm is less than ±2%, instability is better than ±1%/h, which agree with the test data and can meet the requirements of high-precision..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 467 (2013)
Pipeline Filter Algorithm Based on Movement Direction Estimation
DONG Wei-ke, ZHANG Jian-qi, LIU De-lian, and WANG Xiao-rui
Pipeline filter algorithm proposes a solution of detection of dim small target from the perspective of time domain. In terms of detection of weak point target in the strongly undulant infrared sky background, a pipeline filter algorithm is proposed based on motion direction estimation as a method to improve the flaw ofPipeline filter algorithm proposes a solution of detection of dim small target from the perspective of time domain. In terms of detection of weak point target in the strongly undulant infrared sky background, a pipeline filter algorithm is proposed based on motion direction estimation as a method to improve the flaw of detection probability deduction due to the strong interferential noise within the pipeline and low signal noise ratio. The motion characteristics of infrared weak point target are analyzed and the motion direction estimation model was established according to the continuity characteristic of the targets between consecutive frames. Through the model, the prior position information of the targets is detected frame by frame and analyzed in order to estimate the motion direction and trajectory of the targets. The estimation results are used to eliminate the interference on the targets caused by the pipeline inner noises. Experiments and simulation results show that the algorithm can suppress noises in the pipeline effectively, increase the detection probability of the targets, and strengthen the resistance characteristic of the targets against the noises within the pipe..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 471 (2013)
Research on Nonuniformity Correction Algorithm of IRFPA Based on Adjusting Integral Time
CHEN Shi-wei, YANG Xiao-gang, ZHANG Sheng-xiu, and WANG Yi
According to the problems of two temperature points correction algorithm in application, a nonuniformity correction algorithm witch based on adjusting integral time is presented. In this algorithm, the nonlinear image data is translated into the linearized one firstly, then by using the relationship of IRFPA between reAccording to the problems of two temperature points correction algorithm in application, a nonuniformity correction algorithm witch based on adjusting integral time is presented. In this algorithm, the nonlinear image data is translated into the linearized one firstly, then by using the relationship of IRFPA between response characteristic and integral time, the response curve of IRFPA is fitted by adjusting the integral time. And two point calibration correction is used. Finally the exponent of the corrected linearized image data is calculated and the uniformity image of the original one is achieved. The effect of correction aerial infrared image is verified by two temperature points correction algorithm and adjusting the integral time method, and this assessment method for the adaptability of nonuniformity is used in different nonuniformity correction methods. Experimental results indicate that the new algorithm has better engineering practice significance because of its characteristics of small calculating amount and fast speed, and high precision. The algorithm of the nonlinear response model of IRFPA reduces the influence of the detector nonlinear response to the nonuniformity correction performance in large dynamic range in some degree..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 475 (2013)
Influence of Afterburning on Infrared Radiation of Liquid Rocket Exhaust Plume
LIU Zun-yang, SHAO Li, WANG Ya-fu, and SUN Xiao-quan
In order to study the influence of afterburning on the infrared radiation of a liquid rocket exhaust plume, a model was founded which could calculate afterburning flow field and infrared radiation of a liquid rocket exhaust plume. The FLUENT was used to calculate the afterburning flow field of a liquid rocket exhaust pIn order to study the influence of afterburning on the infrared radiation of a liquid rocket exhaust plume, a model was founded which could calculate afterburning flow field and infrared radiation of a liquid rocket exhaust plume. The FLUENT was used to calculate the afterburning flow field of a liquid rocket exhaust plume, the finite rate chemistry reaction model was adopted to calculate the afterburning reaction. Then, a narrow band model based on the HITEMP data base was employed to calculate the radiation parameters of plume gas. Lastly, the finite volume method was used to solve the radiation transfer equation. The feasibility of this model was testified by comparing the calculated spectral radiation intensity of the Titan IIIB exhaust plume and the result of (American) National Aeronautics and Space Administration. By means of this model, the influence of afterburning on the infrared radiation of a liquid rocket exhaust plume was calculated. The results show that, afterburning is able to increase the infrared spectral radiation greatly, and the average increase radio of the two domain radiation bands 2.5~3.0 μm and 4.2~4.7 μm achieve 30.8% and 28.3% respectively. Therefore, the afterburning should be taken into account when calculating the exact infrared radiation of a liquid rocket exhaust plume..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 480 (2013)
A Method of Non-uniformity Correction Based on Adaptively Adjusting Integration Time
LI Jing, ZHU Bin, GUO Li-xin, TANG Lei, and CAO Xiao-he
The real-time correction algorithm is proposed, which adjusts the integration time adaptively according to the current scene information in the process of correction. Firstly, the background images are stored at different integration time and the integration time is adjusted by the specific thresholds. Then the correspThe real-time correction algorithm is proposed, which adjusts the integration time adaptively according to the current scene information in the process of correction. Firstly, the background images are stored at different integration time and the integration time is adjusted by the specific thresholds. Then the corresponding background image is subtracted from the output of IRPPA and the result are taken as the input of neural network. So it can make up the deficiency of neural network, and reduce the non-uniformity caused by the change of integration time. Experiments of real IRFPA videos show that the proposed algorithm insures high quality of image, also has the advantages of integration time adjusting adaptively and real-time correction..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 486 (2013)
Resampling of Piecewise Linear Sequences
DENG Jia-xian, and GUAN Li-na
In order to solve the problems laid on continuous signal sampling based on finite rate of innovationm, the feature of piecewise linear sequences is studied seriously, and a method called sequence resampling is proposed where the continuous signal variation parameters is extracted in discrete domain. The finite rate of In order to solve the problems laid on continuous signal sampling based on finite rate of innovationm, the feature of piecewise linear sequences is studied seriously, and a method called sequence resampling is proposed where the continuous signal variation parameters is extracted in discrete domain. The finite rate of innovation of sequence with finite length is defined, and a parameter extract method called test method is concluded which is suitable for the parameter extract of simple linear sequences, then this method is extended to the one of normal linear sequences. The innovation number does not need to be known in advance, and complex operations in continuous domain can be avoided; the signal′s innovation time and parameters can be extracted from the sampled sequence, and the signal sampling is realized. The proposed algorithm is simulated, and the results show that the proposed algorithm is valid..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 491 (2013)
Image Fusion Algorithm Based on Shift-invariant Shearlet Transform
LIU Wei, YIN Ming, LUAN Jing, and GUO Yu
To overcome the shortcoming of traditional image fusion method based on multi-scale transform, a novel adaptive image fusion algorithm based on shift-invariant shearlet transform (SIST) is proposed. Firstly, the SIST is utilized to decompose the source images, and the low frequency sub-band coefficients and directionalTo overcome the shortcoming of traditional image fusion method based on multi-scale transform, a novel adaptive image fusion algorithm based on shift-invariant shearlet transform (SIST) is proposed. Firstly, the SIST is utilized to decompose the source images, and the low frequency sub-band coefficients and directional bandpass sub-band coefficients are obtained. Secondly, for the low frequency sub-band coefficients, the singular value decomposition method in the gradient domain is used to estimate the local structure information of image, and a variable weights fusion scheme based on the sigmoid function and the extracted features is presented, while for the directional bandpass sub-band coefficients, a scheme based on the Sum-modified-Laplacian (SML) combined with the weighted average scheme is presented. Finally, the fused image is obtained by performing the inverse SIST on the combined coefficients. The experimental results show that the proposed approach can significantly outperform the conventional image fusion methods in terms of both objective evaluation criteria and visual quality..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 4, 496 (2013)
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