Journals >Acta Photonica Sinica
Contents
2013
Volume: 42 Issue 7
23 Article(s)
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Research Article
Dual-blue Wavelength Light-emitting Diodes Based on Varied GaN Barrier Thickness
LI Zheng-kai, YAN Qi-rong, LUO Chang-de, XIAO Han-zhang, and ZHANG Yong
Due to low color rendering index of white light-emitting diodes based on packing of single-blue wavelength chip and Y3Al5O12∶Ce3+ yellow phosphors, using dual-blue wavelength chip, Y3Al5O12∶Ce3+ yellow phoshpor is proposed to realize high color rendering index white emission, and feasibility of the method is analyzed. Due to low color rendering index of white light-emitting diodes based on packing of single-blue wavelength chip and Y3Al5O12∶Ce3+ yellow phosphors, using dual-blue wavelength chip, Y3Al5O12∶Ce3+ yellow phoshpor is proposed to realize high color rendering index white emission, and feasibility of the method is analyzed. Dual-blue wavelength light-emitting diodes based on two pairs of In0.18Ga0.82N/GaN quantum-well and two pairs of In0.12Ga0.88N/GaN quantum-well structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition. Optoelectronic properties of dual-wavelength light-emitting diodes with different GaN barrier thicknesses were also studied. The experimental results indicate that efficient dual-blue-wavelength emission and higher luminescent efficiency are realized from light-emitting diodes by reducing GaN barrier thickness from n-GaN to p-GaN. The a. c. impedance spectroscopy can be explained in terms of the equivalent series circuit model of a set of parallel resistor-capacitor RpCp and a resistor Rs for the dual-blue wavelength light-emitting diodes. Varied GaN barrier thickness can tune parallel resistor and capacitor while it has no effect on series resistor. In addition, Y3Al5O12∶Ce3+ phosphor-converted white light emission with high color rendering index is achieved by use of dual-blue emitting active regions from reducing barrier thickness..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 757 (2013)
All-optical Single-photon Wavelength Conversion Based on Cascaded Sum-frequency Generation and Difference-frequency Generation
LI Wan-jie, ZHU Chang-hua, ZHAO Nan, and PEI Chang-xing
Based on periodically poled lithium niobate (PPLN) waveguides，an all-optical single-photon wavelength conversion scheme is proposed, in which a cascaded sum-frequency generation (SFG) and difference-frequency generation (DFG) are applied. In the Heisenberg picture, the annihilation operators of target photon are obtainBased on periodically poled lithium niobate (PPLN) waveguides，an all-optical single-photon wavelength conversion scheme is proposed, in which a cascaded sum-frequency generation (SFG) and difference-frequency generation (DFG) are applied. In the Heisenberg picture, the annihilation operators of target photon are obtained by using the Hamiltonian of nonlinear conversion process. According to the efficiency of the single-photon wavelength converter, that is, the ratio of the value of photon number operator after conversion to the value before conversion, the relation of the efficiencies of the single-photon wavelength converters in the SFG and DFG process with the pump power are analyzed. The result that there exists an optimum pump power with which the quantum state can be transferred completely is demonstrated. Numerical analysis results show that the efficiency of single-photon wavelength conversion from 1 550 nm to 1 530 nm is about 61% when the pump power of up-converter is 65 mW and the pump power of the down-converter is 150 mW, respectively. In addition, an experimental setup is also proposed, which consists of PPLN waveguides, pump lasers, quasi-single photon source, optical components, e.g. filtering, single photon detector (SPD) and synchronization circuit..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 763 (2013)
Non-visual Effects of Flat Panel Display with Light Emitting Diode Backlight on Human
SONG Li-yan, LI Jun-kai, and MOU Tong-sheng
Aiming at the non-visual effects of optical radiation of the flat panel display with light emitting diode backlight on human circadian rhythms, an experimental system is designed using a model of the evaluation of the circadian factor. By the method of average radiation in total space, the circadian factors of differenAiming at the non-visual effects of optical radiation of the flat panel display with light emitting diode backlight on human circadian rhythms, an experimental system is designed using a model of the evaluation of the circadian factor. By the method of average radiation in total space, the circadian factors of different pictures displayed on flat panel display with light emitting diode backlight are measured, and the pictures are all from the program of Average Picture Level in the International Electrotechnical Commission standard. It is found that the circadian factors of flat panel display with white and majority of colorful backgrounds are above 5.0, which are much stronger than ordinary lighting source, and are closely related to the content is displayed. The result suggests that the non-visual effect of the optical radiation of flat panel display on human circadian rhythms should be considered..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 768 (2013)
Combined with DPVBi Excton Block-layer to Fabricate and Study on Optical and Electronic Performance of the Sub-monolayer OLED
YANG Hui-shan, WU Li-shuang, and PAN Yu-zhuo
A multiple organic light emitting device was fabricated with sub-monolayer technique, of which the structure is ITO/ m-MTDATA(50 nm)/C545T(0.05 nm)/DPVBi (d nm)/DCM2(0.05 nm)/Alq (60 nm)/LiF(1 nm)/Al. C545T and DCM2 sub-monolayer were inserted both the DPVBi sides. Effect of the thickness variation of DPVBi on the deviA multiple organic light emitting device was fabricated with sub-monolayer technique, of which the structure is ITO/ m-MTDATA(50 nm)/C545T(0.05 nm)/DPVBi (d nm)/DCM2(0.05 nm)/Alq (60 nm)/LiF(1 nm)/Al. C545T and DCM2 sub-monolayer were inserted both the DPVBi sides. Effect of the thickness variation of DPVBi on the device performance was studied. As the thickness of DPVBi is 4 nm, the current efficiency is 4.19 cd/A at 4 V and the luminance is 17050 cd/ m2 at 13 V. Experimental results show that the current density-voltage, luminance-voltage, electroluminescence (EL) spectra and the commission internationale de 1′Eclairage coordinates varying voltage, etc. The current efficiency can improved when select the proper thickness of material acting as excton block-layer, which is the lower cavvier mobility and largely negative HOMO position. The results obtained will be helpful for the optimal design and operation of organic light emitting devices, especially for white organic light emitting device using sub-monolayer emitter..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 772 (2013)
Design of High Efficiency Grating Coupler for Vertical Coupling
WU Hua, GUO Xia, and HAN Ming-fu
A high-efficiency grating coupler is designed for vertical coupling between silicon-on-insulator waveguides and single-mode fibers. The reflection characteristics of reflector grating and distributed bragg reflector are employed to obtain a high reflection from the right side and bottom of the coupler. The reflected liA high-efficiency grating coupler is designed for vertical coupling between silicon-on-insulator waveguides and single-mode fibers. The reflection characteristics of reflector grating and distributed bragg reflector are employed to obtain a high reflection from the right side and bottom of the coupler. The reflected light is interfered destructively to reduce the negative second-order reflection by selecting a reasonable spacing between the reflector grating and the coupler grating when the coupler grating is in the vertical coupling. The coupler is optimized using eigenmode expansion-based simulations. The highest coupling efficiency of 89% at a wavelength 1 550 nm is achieved by simulation. The results provide some useful references for the fabrication of the actual vertical coupling grating coupler..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 777 (2013)
Condenser Inside Spherical Solar Cell
XU Yi, SONG Zhao-li, XU Zheng, GUAN Cong, LIU Guo-song, and JIANG Yi
In order to raise utilization ratio of sunlight and photoelectric conversion rate, the inner spherical focusing solar cell structure and the main performance are designed and studied. A Fresnel condenser is used to focus the sun's light onto the inner surface of a ball cavity which is prepared with polycrystalline In order to raise utilization ratio of sunlight and photoelectric conversion rate, the inner spherical focusing solar cell structure and the main performance are designed and studied. A Fresnel condenser is used to focus the sun's light onto the inner surface of a ball cavity which is prepared with polycrystalline silicon photovoltaic cells, implementing concentrating photovoltaic effect on the sphere. By using Inner cavity photon gas model, the light intensity in the inner sphere is analyzed and calculated, the concept of optimum light intensity on the silicon photocell is put forward, and the best condenser multiples for a spherical semiconductor polysilicon batteries of 18 and 9 with the layer thicknesses of 10 μm and 5 μm are calculated. Finite element analysis method is applied to discuss the inside sphere temperature of the solar system. Under the condition of the AM 1.5, 8 times concentration, photovoltaic cells′ maximum temperature is 353.15 K, in the normal scope of work. Active air cooling or water cooling method can greatly increase the convective heat transfer coefficient and decrease the temperature of the photovoltaic cells, and stabilize the work efficiency. By analyzing the constraints of the efficiency of the silicon photocell, the optimize structure of the inner spherical photovoltaic cells is designed; the fill factor can achieve 0.85, and the efficiency of the solar cells inside the spherical condenser can be more than 33% when the sunlight radiation power is 800 mW/cm2..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 782 (2013)
Responsivity Variation with Temperature of Uncooled Mid-infrared HgCdTe Photoconductive Detector
FENG Guo-bin, ZHANG Jian-min, YANG Peng-ling, WANG Qun-shu, and AN Yu-ying
To measure the mid-infrared deuterium fluoride laser irradiance distribution, a laser beam profile diagnostic system based on uncooled mid-infrared HgCdTe photoconductive detector array is developed. Because the mid-infrared detector is very sensitive to work temperature, it is necessary to quantitatively analyze its tTo measure the mid-infrared deuterium fluoride laser irradiance distribution, a laser beam profile diagnostic system based on uncooled mid-infrared HgCdTe photoconductive detector array is developed. Because the mid-infrared detector is very sensitive to work temperature, it is necessary to quantitatively analyze its temperature characteristics for evaluating the measuring uncertainty of the system and providing the criterion of selecting the satisfactory detector. The responsivity of HgCdTe photoconductive detector related with temperature and wavelength is analyzed. It is deduced that the responsivity can be expressed as a variable-separate function of temperature and wavelength under special conditions. The assumption is validated by the experiment，of which the responsivity of uncooled mid-infrared HgCdTe photoconductive detector in (－40~+30) ℃ is measured with 3.8 μm and 1.31 μm lasers. Based on the results, a simple and practical method to measure the temperature characteristic of the responsivity of uncooled MIR HgCdTe detector is presented..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 787 (2013)
Travelling Wave Deflecting Characteristics of Streak-tube
LI Hao, TIAN Jin-shou, LI Yan, WANG Chao, WEN Wen-long, WANG Jun-feng, and WANG Xing-chao
In order to obtain deflection device having wide bandwidth, small dispersion and high deflection sensitivity, a kind of traveling wave deflector is designed. Using commercial electromagnetic simulation software CST finite element method, bandwidth of traveling wave deflector in streak camera is studied, and the travellIn order to obtain deflection device having wide bandwidth, small dispersion and high deflection sensitivity, a kind of traveling wave deflector is designed. Using commercial electromagnetic simulation software CST finite element method, bandwidth of traveling wave deflector in streak camera is studied, and the travelling wave deflector characteristics of dispersion curves, characteristic impedance changing with frequency and electron beam deflecting function are studied numerically using finite integration method. The comparison of deflecting sensitivity between traveling wave deflector and traditional plating deflector is made. Moreover, the electric field distribution in traveling wave deflector with sinewave scanning voltage signal is simulated. The results show that bandwidth of sharp top deflector is bigger than that of round top deflector and that bandwidth becomes smaller when legs of deflector become longer, with the biggest bandwidth of 7 GHz; phase velocity and group velocity decrease with the increasing of frequency; when frequency increases, a peak value exists for characteristic impedance; under the same dimensions, the deflecting sensitivity of travelling wave detector is two times higher than that of plating deflector; the electric field produced by sinewave scanning voltage appears periodic; the designed traveling wave deflector has wide bandwidth, of which dispersion is small in wide frequency range, and it can effectively make electron beam deflect..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 792 (2013)
Inspection Focus Technology Based on Astigmatic Method for Linear CCD Camera
WANG Zhi
The target plane of the space tridimensional mapping camera will be deviated from the focal plane, under the condition of space environment and vibration, impact when satellite is launching, and image resolution ratio will be descended because of defocusing. For tridimensional mapping camera, principal point position aThe target plane of the space tridimensional mapping camera will be deviated from the focal plane, under the condition of space environment and vibration, impact when satellite is launching, and image resolution ratio will be descended because of defocusing. For tridimensional mapping camera, principal point position and focal length variation of the camera affect positioning accuracy of ground target. In order to revise the shortage of photoelectric encoder utilization, the measuring and focusing method was put forward based on astigmation. A quadrant detector was adopted to measure the astigmation caused by the deviation of the target plane, refer to calibrated relation between the target plane poison and the asrigmation, so the deviation vector of the target plane can be obtained. This method includes all factors caused deviation of the target plane, and experimental results show that the focusing resolution of mapping camera focusing mechanism based on astigmatic method can reach 0.025 mm..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 797 (2013)
Next Generation of Space Wireless Communication Technology Based on X-ray
ZHAO Bao-sheng, WU Chuan-xing, SHENG Li-zhi, and LIU Yong-an
In the field of space wireless communication, laser and microwave technology have become mature, but bottleneck problems such as the limited transmission distance, the limited communication rate and so on already exist, which restrict the future applications in deep space. As a result of its short wavelength and great In the field of space wireless communication, laser and microwave technology have become mature, but bottleneck problems such as the limited transmission distance, the limited communication rate and so on already exist, which restrict the future applications in deep space. As a result of its short wavelength and great penetrability, X-ray has no attenuation for transmission in space when its photon energy is more than 10keV (λ<0.1nm). Thus, via X-ray, a communication technology of long distance signal transmission in space can be achieved with smaller volume, lower weight and lower power. However, studies on X-ray communication and its applications still remain blank in China presently. X-ray communication was proposed and defined as a “revolutionary concept” by National Aeronautics and Space Administration of USA just a short time ago. Thus, the study on this novel space communication method with a new conception by using X-ray as information carrier will have a great scientific significance and applicable prospect. X-ray communication technology will not only be a good complement to laser and microwave communications, but will also have a unique performance on those occasions where laser and microwave could have been shielded. Study on space wireless communication technology based on X-ray will include: the theoretical research on X-ray space transmission; the research on a high power and wide bandwidth(GHz) modulated X-ray source for pulse signal; the research on high speed, week signal of X-ray detection technology; the research on acquisition, tracking and pointing technology of X-ray space communication; the research on high efficient coding theory and technology..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 801 (2013)
Investigation on Evaluation Theory of Fiber Bragg Grating Tensile Fatigue Property
SHU Yue-jie, CHEN Wei-min, ZHANG Peng, LIU Hao, ZHANG Wei, and LIU Xian-ming
Fiber Bragg Grating(FBG) tensile fatigue property seriously affects the long term reliability of FBG strain sensors. To evaluate FBG tensile fatigue property, the package of FBG sensors is analyzed, and the surface mounting FBG is selected to study the FBG tensile fatigue property. To distinguish the tensile fatigue siFiber Bragg Grating(FBG) tensile fatigue property seriously affects the long term reliability of FBG strain sensors. To evaluate FBG tensile fatigue property, the package of FBG sensors is analyzed, and the surface mounting FBG is selected to study the FBG tensile fatigue property. To distinguish the tensile fatigue signal of FBG from the bonding layer, the property of the grating reflection spectrum is proposed as the evaluation index of FBG, and sensing characteristics is proposed as the evaluation index of bonding layer. The grating reflection spectrum evaluation index includes side mode suppression ratio and the 3 dB bandwidth. And the sensing characteristics evaluation index includes sensitivity, linearity and the strain transfer efficiency rate. To verify this theory, an experiment based on equal strength beam is conducted, in which the amplitude of “AC” strain is 500 micro strains, and the frequency is 18 Hz. After 10 million tensile fatigue tests on three FBG sensors, the average bandwidth increase 2.07%, the strain transfer efficiency rate decrease 4.5%, and the sensitivity decrease 3.9%. The experiment results show that this theory is workable..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 805 (2013)
Effect of Substrate Temperature on the Properties of Textured Ag/AZO Back Electrodes Prepared by Magnetron Sputtering
WANG Chun-lei, WANG Chao, and MAO Yan-li
By optimizing the back reflection electrode of the thin-film silicon-based solar cell, the back reflection electrode surface appears the homogeneous pyramid-structure, which can increase the effective optical-path of the incoming light, and the photon capture rate, thereby the photoelectric conversion efficiency of theBy optimizing the back reflection electrode of the thin-film silicon-based solar cell, the back reflection electrode surface appears the homogeneous pyramid-structure, which can increase the effective optical-path of the incoming light, and the photon capture rate, thereby the photoelectric conversion efficiency of the thin-film silicon solar cells is improved. In this paper, the Ag/AZO(ZnO:Al) conductive films were prepared on glass substrates by magnetron sputtering. In the case of the other sputtering parameters being optimal, the photovoltaic properties and surface morphology of AZO/Ag of the different substrate temperatures were investigated emphatically. The study shows that the film haze factor in the visible region first increases and then decreases; when the substrate temperature is 500℃, the haze factor of the film is the maximum with an average of more than 95% in the visible range; the resistivity of the film increases gradually with the increase of the substrate temperature, and the resistivity increases quickly when the substrate temperature is higher than 500℃. Considering the optical and electrical properties of the conductive films, when the substrate temperature is 500℃, the surface haze value of the tandem conductive films is the best and its resistivity is very small, which will play a significant role in improving the performance of the solar cells..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 812 (2013)
Calculation of Pseudo-brewster Angle for Substrate and Thin Film-substrate System
LIU Hua-song, JIANG Yu-gang, WANG Li-shuan, JIANG Cheng-hui, and JI Yi-qin
Numerical calculation of pseudo-Brewster angles for substrate and thin-film substrate system is demonstrated. The results show: for only substrates, pseudo-Brewster angles are mainly affected by refractive index when the extinction coefficient is lower than 0.01; when the extinction coefficient is above 0.1, the pseudoNumerical calculation of pseudo-Brewster angles for substrate and thin-film substrate system is demonstrated. The results show: for only substrates, pseudo-Brewster angles are mainly affected by refractive index when the extinction coefficient is lower than 0.01; when the extinction coefficient is above 0.1, the pseudo-Brewster angle is also modulated by the extinction coefficient. The studies indicate: for thin film-substrate systems, pseudo-Brewster angle is influenced by both refractive index and physical thickness of thin film together with optical constants of substrate; in the HfO2 film on silicon and fused silica substrate systems, pseudo-Brewster angles exhibit quasi-periodic characteristic with variation of incident wavelength or thin film thickness, as caused by interference effect..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 817 (2013)
Comparison of Base-catalyzed Silica Antireflective Coatings Modified by Different Surface Treatments of Water-NH3 and/or Hexamethyldisilazane Vapors
HUO Yan-fang, LUO Rong-hui, and SU Yong-gang
Aiming at the shortcoming that base-catalyzed quarter-wave silica antireflective coatings, prepared by sol-gel method, are porous and therefore low environment-resistant, water/NH3 vapor and/or hexamethyldisilazane vapor were utilized to modify the surface of these coatings to obtain high hydrophobicity and abrasion-reAiming at the shortcoming that base-catalyzed quarter-wave silica antireflective coatings, prepared by sol-gel method, are porous and therefore low environment-resistant, water/NH3 vapor and/or hexamethyldisilazane vapor were utilized to modify the surface of these coatings to obtain high hydrophobicity and abrasion-resistance. Otherwise, comparison between different modified results from single vapor and combined vapors, were carried out to show the changes of coatings’ physical properties and microstructures after different surface modifications and the influence of the treated order of combined vapors to the result coatings. According to the investigations, some conclusion can be drawn that water-ammonia vapor treatment facilitates the cross-link between hydroxyl groups in coatings, which reduces the film thickness, strengthens the abrasion-resistance, and simultaneously maintains the high transmittance; hexamethyldisilazane vapor treatment introduces methyl groups into coatings, making the polarity of coating surface and the interaction between particles decreased obviously, leading to poorer abrasion-resistance but fortunately, distinctly improved hydrophobicity; when coatings are treated by water-ammonia combined hexamethyldisilazane vapor, the water-ammonia vapor firstly strengthens the abrasion-resistance and meanwhile reduces the amount of hydroxyl groups which hindered the later hexamethyldisilazane vapor treatment, finally obtaining AR coatings with good abrasion-resistance and a certain extent of hydrophobicity; when coatings are treated by hexamethyldisilazane combined water-ammonia vapor, the hexamethyldisilazane vapor obviously improves the hydrophobicity but weakens the effect of water-ammonia vapor, resulting in a slight weaker abrasion-resistance compared to that after single water-ammonia vapor treatment..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 823 (2013)
Influence of Detector Sampling Frequency to Optics Diffraction Frequency Ratio on Aviation Image
DING Shuai, KUANG Hai-peng, WANG De-jiang, XU Zheng-ping, and DING Ya-lin
The Q of a digital imaging system defines how these two limitations are balanced in the camera design. The image quality in different Q values was simulated and compared. During the design phase, a tradeoff between optical resolution and detector resolution limitations ensues regarding the best Q for an imaging system.The Q of a digital imaging system defines how these two limitations are balanced in the camera design. The image quality in different Q values was simulated and compared. During the design phase, a tradeoff between optical resolution and detector resolution limitations ensues regarding the best Q for an imaging system. A Q=2 design seems to offer the best image quality from a fundamental resolution perspective, however, other factors such as signal to noise ratio(SNR), scene area and motion blur can push the design to a lower Q. The best Q for the design is determined by performing careful trade studies. Q value can be used as a directory indicator in imaging system design..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 828 (2013)
Image Metric Analysis of Laser Jamming Effect Based on Wavelet Energy and Spot Size
WU Yun-long, SHAO Li, ZHANG Kai, LI Feng, and SUN Xiao-quan
The influence of laser jamming on CCD imaging system is introduced. The similarity between laser jamming image and background clutter is illuminated in the view of their influence on electro-optical imaging detection system. Aiming at the frequency characteristic of laser jamming image and combining with background cluThe influence of laser jamming on CCD imaging system is introduced. The similarity between laser jamming image and background clutter is illuminated in the view of their influence on electro-optical imaging detection system. Aiming at the frequency characteristic of laser jamming image and combining with background clutter metrics in machine vision, a comprehensive image metric for describing laser jamming effect is proposed by taking advantage of the predominance of wavelet analysis, based on wavelet energy and spot size. The wavelet analysis on typical laser jamming images indicates that the approximation coefficients and detail coefficients will both increase with the raise of laser power; the laser spot in jamming image can be regarded as the approximation coefficients, and the laser speckle around the spot can be seen as detail coefficients, which is similar to the salt noise. Laser jamming experiment in the field of view and simulative calculation show that laser jamming can reduce the segmentation accuracy of Otsu method, and raise the false alarm probability of correlation method. The metric can avoid the weaknesses of spot metric and wavelet energy metric. Hence, it is able to reflect the performance of laser jamming on CCD imaging system in the field of view properly..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 832 (2013)
An Infrared Target Detection Algorithm Based on Knowledge Model
SU Juan, YANG Luo, and LU Jun
Based on analyzing the infrared characteristics and shape characteristics of condensing tower that has special construction rules, an infrared target detection algorithm based on knowledge model is proposed. Firstly, based on the infrared characteristics of condensing tower, the intensity, orientation and local entropyBased on analyzing the infrared characteristics and shape characteristics of condensing tower that has special construction rules, an infrared target detection algorithm based on knowledge model is proposed. Firstly, based on the infrared characteristics of condensing tower, the intensity, orientation and local entropy features are extracted to construct the visual attention model, which is used to extract salient regions as regions of interest in the infrared image. Secondly, based on the shape characteristics of condensing tower, hyperbola shape model is constructed for condensing tower, structure feature edges are extracted in the salient regions and used to fit the hyperbola shape model, and relevant decision rules are constructed to confirm the targets. The recall and precision of the experiment on a set of air-born infrared images can reach up to 98.67% and 93.67% respectively, which demonstrates the excellent performance of the proposed algorithm. Moreover, since the reference image is unnecessary in the proposed algorithm, the requirements for the data preparation is reduced greatly, which improve the practicality of the algorithm..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 839 (2013)
Space Target Dual-band IR Imaging Thermometry
LIU Ying-qi
The earth′s heat radiation, as one of the unknown parameters between the space target and ground-based telescopes infrared imaging terminal, will reduce the traditional dual-band pyrometry forward accuracy. To improve the accuracy of target temperature estimation, an estimation function based on the measured number of The earth′s heat radiation, as one of the unknown parameters between the space target and ground-based telescopes infrared imaging terminal, will reduce the traditional dual-band pyrometry forward accuracy. To improve the accuracy of target temperature estimation, an estimation function based on the measured number of electrons is established, and temperature inversed solution model for solving the maximum likehood function is obtained; dual-band forward solution method based on the number of electrons is derived, and the simulation and analysis of the algorithm is performed. The experimental results indicate that the target temperature inversion precision has a close relationship with the imaging detector signal-to-noise ratio, the earth′s thermal radiation estimation accuracy and emissivity difference between bands; when the signal-to-noise ratio is relatively low, the dual-band pyrometry is in no solution; when the signal-to-noise ratio is relatively high, the inversion temperature accuracy of the dual-band pyrometry and maximum likelihood function is quite; function method of maximum likelihood using constraints and limited memory quasi-Newton optimization algorithm can effectively avoid the objective function into a local minimum; maximum likelihood function method has a strong ability to resist noise interference, can expand the scope of object temperature solution, and with high precision; under the guarantee of signal-to-noise ratio, increasing the number of image-band in order to improve the accuracy of temperature inversion..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 845 (2013)
A Small IR Target Detection and Tracking Algorithm Based on Morphological and Genetic-particle Filter
WANG Ling-ling, and XIN Yun-hong
Aiming at small IR target dectection and tracking in complex background, a method based on the top-hat detection algorithm, genetic algorithm and particle filter is presented. Firstly, a sub-frame extracting method is used for the removal of the background and noise around target, which effectively reduces the number oAiming at small IR target dectection and tracking in complex background, a method based on the top-hat detection algorithm, genetic algorithm and particle filter is presented. Firstly, a sub-frame extracting method is used for the removal of the background and noise around target, which effectively reduces the number of pixels participating in operation; secondly, a few structures with different edge characteristics are introduced in the top-hat algorithm, which greatly improve the efficient for the detection of the pre-target from sub-frame; thirdly, based on the correlation of target movement in time and space domain, a threshold judgment technology is used to remove the false targets; finally, the genetic algorithm is introduced into the particle filtering to enhance the diversity of particles, which can effectively improve the real-time and the precision of target tracking. The experimental results show that the presented algorithm has obvious superiority in detection correctness and tracking accuracy and robustness..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 849 (2013)
Interactive Rendering for Realistic Face via Three-layer Material Model
YANG Meng-zhao, WANG Kuan-quan, and ZUO Wang-meng
An interactive rendering platform is designed based on three-layer material model. The specular reflection of human skin is approximated based on the bidirectional reflectance distribution function, and the subsurface scattering is effectively simulated using sum-of-Gaussians blur and texture coordinates stretch correcAn interactive rendering platform is designed based on three-layer material model. The specular reflection of human skin is approximated based on the bidirectional reflectance distribution function, and the subsurface scattering is effectively simulated using sum-of-Gaussians blur and texture coordinates stretch correction. Combining specular reflection with subsurface scattering, the final real-time rendering for realistic face is obtained. The interactive platform provides a friendly interface for user to operate digital character, views the reflection and scattering effect when the incoming light is rotating, adds high-dynamic range environment map in real-time, and adjusts intensity of illumination and degree of blur, which greatly help user to control and design digital character..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 857 (2013)
A No-reference Assessment Model for Video Quality Based on Movement Activity
YU Chun-yan, WU Li-li, CHEN Guo-long, and ZHENG Wei-hong
It is necessary to assess network video quality in real-time that depends on network transmission statement to subjective visual without any referenced video sequences. Focusing on distortion of videos caused by network packet loss, it is found that network packet loss in different frames with different decoding types It is necessary to assess network video quality in real-time that depends on network transmission statement to subjective visual without any referenced video sequences. Focusing on distortion of videos caused by network packet loss, it is found that network packet loss in different frames with different decoding types causes different sustained effects of video distortion, and it exists significant association between visual feelings caused by network packet loss and movement activity of lost video content. Hence, a no-reference assessment model for video quality is proposed based on movement activity. This model analyzes the damage caused by the packet loss of the code stream received by client, and marks the damaged macro block to associate the damaged macro blocks′ distortion continuing effect and movement activity with videos' quality. Then, it completes the quality assessment of videos without reference of any original video sequence or video decoding. Experimental results show that this method has a small amount of calculation, a high real-time and a high degree of consistency with the subjective assessment results..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 864 (2013)
An Improved Method of Image Fast Defogging
PANG Chun-ying, JI Xiao-qiang, SUN Li-na, and LANG Xiao-long
In order to improve degraded image clarity and color fidelity in foggy weather, an improved defogging method based on dark-channel prior is proposed. According to the more computation time，and on the premise of defogging effect, fast bilateral filtering is used instead of soft matting to refine transmission map that reIn order to improve degraded image clarity and color fidelity in foggy weather, an improved defogging method based on dark-channel prior is proposed. According to the more computation time，and on the premise of defogging effect, fast bilateral filtering is used instead of soft matting to refine transmission map that reduces the complexity of the algorithm greatly. The processing time is 5% of original method，which can meet the real-time requirements of the general engineering. Since the brightness of image after haze removal is lower than the actual scene and the color is dim, a simple and effective method of image contrast and brightness enhancement is proposed. It adaptively enhances the image brightness, and modifies the local contrast which is due to the thick fog and haze. The experimental results indicates that this method can restore the fog scene and color rapidly and effectively, and guaranteed the stability and reliability of outdoor imaging system in bad weather in a certain extent..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 872 (2013)
Multigrid Algorithm Based on Transport of Intensity Equation
LIU Hong, TAO Shao-jie, CHENG Hong, and HUANG Jiang-lin
Multigrid algorithm based on the transport of intensity equation is researched to retrieval phase information from the intensity measurement. Given initial value and stared from the coarsest grid, a solution is obtained by calculating; regarded it as the finest initial value, an approximate solution is obtained by calcMultigrid algorithm based on the transport of intensity equation is researched to retrieval phase information from the intensity measurement. Given initial value and stared from the coarsest grid, a solution is obtained by calculating; regarded it as the finest initial value, an approximate solution is obtained by calculating; then its residual is calculated and it is restricted to coarser grid and solving, until to the coarsest grid, followed by corrected the solution of finer grid. Finally, different frequency error components are eliminated by cycle which on different sizes grids, and the accurate solution is obtained. The simulation and real experiments show that the multigrid algorithm can well retrieve the actual phase of the object from the intensity image..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 878 (2013)
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