2014
2014
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Record 217 of
Title:Graded index microstructured polymer fiber for terahertz applications
Author(s):Ma, Tian(1,2); Skorobogatiy, Maksim(1); Wang, Lili(2)Source: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz Volume: Issue: DOI: 10.1109/IRMMW-THz.2014.6955999 Published: November 13, 2014Abstract:A novel graded index microstructured polymer THz fiber, whose graded index profile is achieved by a hexagonal subwavelength air-hole array with graded diameters, is studied. The simulation results show that this geometry design can reduce the dispersion and the confinement loss significantly. ? 2014 IEEE.Accession Number: 20144800265259 -
Record 218 of
Title:Design of infrared imaging system with adaptive correction function
Author(s):Wang, Huawei(1,2); Cao, Jianzhong(1); Ma, Caiwen(1); Zhang, Hui(1); Wu, Dengshan(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 1 DOI: Published: January 2014Abstract:In view of the fact that the response of IRFPA will drift with time and temperature and the IR imaging system will be used to measure and watch, an long-wave infrared uncooled imaging system which has adaptive correction function was designed. The system is based on FPGA, in which FPGA performs system control and image processing. Architecture of the system is simple and with less power dissipation. In order to improve the performance of the detector, a temperature control circuit based on ADN8830 was introduced, which could set temperature of the detector to a fixed point. In order to correct non-uniform responses of the detector' s individual elements, an adaptive non-uniformity correction algorithm was proposed based on shutter, which could compensate the response drift according to temperature and time. The system had both analog and digital video output, in which analog video could be used to watch, while digital video with 12 bit precision could be used to measure. The results show that the imaging system has the advantages of good image quality, good environmental adaptability and low power consumption.Accession Number: 20141017420243 -
Record 219 of
Title:Iterative interpolation algorithm of Bayer images based on color difference space
Author(s):Liang, Xiaofen(1,2); Qiao, Weidong(1); Yang, Jianfeng(1); Xue, Bin(1); Qin, Jia(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 9 DOI: Published: September 25, 2014Abstract:Signal CCD/CMOS sensors capture image information by covering the sensor surface with a color filter array (CFA). For each pixel, only one of three primary colors(red, green and blue) can pass through the CFA. The other two missing color components are estimated by the values of surrounding pixels. The first step was to estimate interpolation direction taking advantage of the pixels in 5×5 template and use the optimal weighting factors to interpolate G components. The second step was to interpolate R(B) components at the location of B(R) using the interpolation operator based on two-dimensional rational function. The third step was to interpolate R and B components at the location of G components by color difference interpolation. Lastly, the iterative interpolation repeated until approaching the optimal results using variance-constrained condition. Through Matlab simulate experiments based on 24 Kodak images and the images captured from our camera, the proposed algorithm outperforms both in visual and numerical aspects.Accession Number: 20144400132260 -
Record 220 of
Title:Laser wave-front measuring based on quadri-wave lateral shearing interferometry
Author(s):Ren, Juan(1,2); Luo, Xiu Juan(1); Xia, Ai Li(1); Zhang, Yu(1,2)Source: Applied Mechanics and Materials Volume: 568-570 Issue: DOI: 10.4028/www.scientific.net/AMM.568-570.50 Published: 2014Abstract:Quadri-wave lateral shearing interferometry(QWLSI) is a new and powerful technique for wave-front measurement. This paper deduced the principle of QWLSI in details, showed a Fourier analysis of the resulting interferogram, then obtained a wave-front with high accuracy and minimum reconstruction error by using the least square method. Finally a 532nm laser was measured to validate the reconstruction, and the error analysis was discussed in practical laser metrology. It is concluded that QWLSI provides a better choice for the adaptive optics as compared with traditional lateral shearing interferometer(TLSI) and Shack-Hartmann(S-H) wave-front sensor. ? (2014) Trans Tech Publications, Switzerland.Accession Number: 20142717908315 -
Record 221 of
Title:PST research and measurement of lunar-based optical telescope stray light
Author(s):Xu, Liang(1,2); Zhao, Jianke(1); Xue, Xun(1); Zhou, Yan(1); Liu, Feng(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 4 DOI: Published: April 2014Abstract:To verify suppression capability of the stray light of the lunar-based optical telescope (LOT), its stray light rejection ratio of glare shield out of field range by point source transmittance on ground was tested, and assessing its stray light rejection ratio with PST of optical system diversity angle of offaxis. The new test method of PST breaks through the tradition method of stray light, using a new method that is combining high degree of accuracy star simulator with EMCCD, guaranteeing that the detector has large dynamic region within its linear range, and the dynamic range is 1012. It could satisfy the indexing demand that the PST testing result is 10-7 (at 22°angle of off-axis). This test method could objectively and directly reflect the stray light rejection ratio of glare shield. The testing uncertainty of PST is above 60%, it will exceed the testing precision of classical stray light testing method. Moreover, discussing the improving method, the target PST testing result will reach 10-12. Last it verify the PST of LOT catering design demand with the experiment that it test stray light rejection ratio of glare shield.Accession Number: 20142217774893 -
Record 222 of
Title:Spectroscopic properties of Yb3+-doped TeO2 - BaO - BaF2 - Nb2O5-based oxyfluoride tellurite glasses
Author(s):Lin, She-Bao(1,2); Wang, Peng-Fei(1); She, Jiang-Bo(1); Guo, Hai-Tao(1); Xu, Shen-Nuo(1,2); Yu, Cheng-Long(3); Liu, Chun-Xiao(4); Peng, Bo(1,5)Source: Chinese Physics B Volume: 23 Issue: 9 DOI: 10.1088/1674-1056/23/9/097801 Published: 2014Abstract:A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, (15 mol%-x) BaO, x BaF2 (x = 0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm2 to 1.21 pm2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser. ? 2014 Chinese Physical Society and IOP Publishing Ltd.Accession Number: 20164202907478 -
Record 223 of
Title:Adaptive fusion of particle filtering and spatio-temporal motion energy for human tracking
Author(s):Zhou, Huiyu(1); Fei, Minrui(2); Sadka, Abdul(3); Zhang, Yi(4); Li, Xuelong(5)Source: Pattern Recognition Volume: 47 Issue: 11 DOI: 10.1016/j.patcog.2014.05.006 Published: November 2014Abstract:Object tracking is an active research area nowadays due to its importance in human computer interface, teleconferencing and video surveillance. However, reliable tracking of objects in the presence of occlusions, pose and illumination changes is still a challenging topic. In this paper, we introduce a novel tracking approach that fuses two cues namely colour and spatio-temporal motion energy within a particle filter based framework. We conduct a measure of coherent motion over two image frames, which reveals the spatio-temporal dynamics of the target. At the same time, the importance of both colour and motion energy cues is determined in the stage of reliability evaluation. This determination helps maintain the performance of the tracking system against abrupt appearance changes. Experimental results demonstrate that the proposed method outperforms the other state of the art techniques in the used test datasets. ? 2014 Elsevier Ltd.Accession Number: 20143017965692 -
Record 224 of
Title:Observation of multipulse bunches in a graphene oxide passively mode-locked ytterbium-doped fiber laser with all-normal dispersion
Author(s):Huang, Shisheng(1); Wang, Yonggang(2); Peiguang, Yan(1); Zhang, Gelin(1); Zhao, Junqing(1); Li, Huiquan(1); Lin, Rongyong(1); Cao, Guangzhong(3); Duan, Ji'An(4)Source: Applied Physics B: Lasers and Optics Volume: 116 Issue: 4 DOI: 10.1007/s00340-014-5780-7 Published: September 2014Abstract:We give a systematic experimental study of multipulse bunches in a graphene oxide saturable absorber (GOSA) passively mode-locked all-normal dispersion ytterbium-doped fiber laser (YDFL). Some special phenomena such as harmonic multipulse bunches, harmonic mode-locking, and chaotic multipulse states are also obtained. Our experiment reveals that the inserted 2.5-nm narrow bandwidth filter plays an important role in the formation of multipulse in all-normal dispersion fiber lasers. Because of the effective gain bandwidth depends on both the 2.5-nm narrow bandwidth filter and the artificial fiber birefringence filter, the multipulse operation states are sensitive to the polarization. It is the first demonstration of multipulse evolution in a GOSA passively mode-locked all-normal dispersion YDFL. ? 2014 Springer-Verlag Berlin Heidelberg.Accession Number: 20143618141173 -
Record 225 of
Title:Image super-resolution via low-rank representation
Author(s):Li, Zhao(1,2); Wang, Le(1); Yu, Tao(1,2); Hu, Bing Liang(1)Source: Applied Mechanics and Materials Volume: 568-570 Issue: DOI: 10.4028/www.scientific.net/AMM.568-570.652 Published: 2014Abstract:This paper presents a novel method for solving single-image super-resolution problems, based upon low-rank representation (LRR). Given a set of a low-resolution image patches, LRR seeks the lowest-rank representation among all the candidates that represent all patches as the linear combination of the patches in a low-resolution dictionary. By jointly training two dictionaries for the low-resolution and high-resolution images, we can enforce the similarity of LLRs between the low-resolution and high-resolution image pair with respect to their own dictionaries. Therefore, the LRR of a low-resolution image can be applied with the high-resolution dictionary to generate a high-resolution image. Unlike the well-known sparse representation, which computes the sparsest representation of each image patch individually, LRR aims at finding the lowest-rank representation of a collection of patches jointly. LRR better captures the global structure of image. Experiments show that our method gives good results both visually and quantitatively. ? (2014) Trans Tech Publications, Switzerland.Accession Number: 20142717908431 -
Record 226 of
Title:Contrast enhancement-based forensics in digital images
Author(s):Cao, Gang(1,2); Zhao, Yao(1,3); Ni, Rongrong(1,4); Li, Xuelong(5)Source: IEEE Transactions on Information Forensics and Security Volume: 9 Issue: 3 DOI: 10.1109/TIFS.2014.2300937 Published: March 2014Abstract:As a retouching manipulation, contrast enhancement is typically used to adjust the global brightness and contrast of digital images. Malicious users may also perform contrast enhancement locally for creating a realistic composite image. As such it is significant to detect contrast enhancement blindly for verifying the originality and authenticity of the digital images. In this paper, we propose two novel algorithms to detect the contrast enhancement involved manipulations in digital images. First, we focus on the detection of global contrast enhancement applied to the previously JPEG-compressed images, which are widespread in real applications. The histogram peak/gap artifacts incurred by the JPEG compression and pixel value mappings are analyzed theoretically, and distinguished by identifying the zero-height gap fingerprints. Second, we propose to identify the composite image created by enforcing contrast adjustment on either one or both source regions. The positions of detected blockwise peak/gap bins are clustered for recognizing the contrast enhancement mappings applied to different source regions. The consistency between regional artifacts is checked for discovering the image forgeries and locating the composition boundary. Extensive experiments have verified the effectiveness and efficacy of the proposed techniques. ? 2005-2012 IEEE.Accession Number: 20141117440210 -
Record 227 of
Title:Image super-resolution via saliency sparse representation
Author(s):Zhang, Xue Jun(1,2); Hu, Bing Liang(1)Source: Applied Mechanics and Materials Volume: 568-570 Issue: DOI: 10.4028/www.scientific.net/AMM.568-570.659 Published: 2014Abstract:The paper proposes a new approach to single-image super resolution (SR), which is based on sparse representation. Previous researchers just focus on the global intensive patch, without local intensive patch. The performance of dictionary trained by the local saliency intensive patch is more significant. Motivated by this, we joined the saliency detection to detect marked area in the image. We proposed a sparse representation for saliency patch of the low-resolution input, and used the coefficients of this representation to generate the high-resolution output. Compared to precious approaches which simply sample a large amount of image patch pairs, the saliency dictionary pair is a more compact representation of the patch pairs, reducing the computational cost substantially. Through the experiment, we demonstrate that our algorithm generates high-resolution images that are competitive or even superior in quality to images produced by other similar SR methods. ? (2014) Trans Tech Publications, Switzerland.Accession Number: 20142717908432 -
Record 228 of
Title:A gradient threshold auto-focus algorithm
Author(s):Mo, Chunhong(1,2); Liu, Bo(1); Ding, Lu(1); Chen, Errui(1); Guo, Gao(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 1 DOI: Published: January 2014Abstract:Traditional gradient auto-focus algorithms have large amount of calculation which will cause the reduction of real-time performance. These algorithms are also weak in anti-noise capability which will result in the decline of unimodality and sensitivity. So a gradient threshold auto-focus algorithm was proposed to improve the focusing performance to meet the requirements of real time and accuracy in auto-focusing subsystem of photoelectric tracking system. The proposed algorithm took the local variance as a local threshold to distinguish the edge pixels from non-edge pixels. Then it used a kind of new standard deviation of the whole image as a global threshold to weaken the effects of noise and background. At last, it used one of traditional gradient auto-focus algorithms to calculate the focusing value of the pre-processed image for clarity-evaluation. The results of lots of experiments show that the proposed algorithm has good real- time performance, strong unimodality, high sensitivity and powerful anti-noise capability. When the proposed algorithm is used in the auto-focusing subsystem of photoelectric tracking system, all the attractive performances remain, which traditional gradient auto-focus algorithm can't achieve.Accession Number: 20141017420289