LASIS高光谱图像的3D-SPECK压缩算法

将三维集合分裂嵌入块编码算法结合感兴趣区域的压缩方案用于大孔径静态干涉成像光谱仪图像压缩.首先,对高光谱干涉图像序列进行三维非对称离散小波变换.其次,定义零块树作为编码单位.采用感兴趣区域方法对不同的编码单位赋予不同的比特率,以保护光谱信息.最后,采用改进的三维集合分裂嵌入块编码算法分别对每个编码单位进行编码.实验结果表明,该方案在8:1压缩比下,获得大于40dB的峰值信噪比,同时有效地保护了光谱信息.该算法复杂度低,实时性好,满足大孔径静态干涉成像光谱仪系统图像压缩要求.     

大孔径静态干涉光谱仪图像压缩技术

从图像压缩的角度分析了大孔径静态干涉成像光谱仪成像原理，并提出了一种新的遥感多光谱图像压缩方案。新方案利用大孔径静态干涉成像光谱仪推扫成像特点提出了一种低存储量，帧间小波域匹配的图像序列压缩方法，提高图像质量3～4dB。为了保证图像的光谱信息在8倍压缩比下有效应用，系统采用了一种新的感兴趣区域(ROD编码技术。感兴趣区域编码时，由于方案中采用率失真优化斜率提升，而不是比特平面移位，从而使图像在相同的光谱分辨率下拥有更好的空间分辨率。实验结果表明，算法大大保护了图像的光谱特性，在8倍压缩比下，满足了该类干涉多光谱遥感图像的质量要求。     

一种干涉高光谱图像的3DSPIHT结合ROI压缩算法

针对大孔径静态干涉成像光谱仪的成像特点,提出了一种基于三维小波变换的3DSPIHT算法结合ROI的图像压缩方案.对干涉高光谱图像序列进行了三维非对称离散小波变换.采用ROI方法对主要的光谱系数进行提升,以保护光谱信息.最后,对3DSPIHT算法进行改进,以有效编码干涉高光谱图像的小波变换系数.实验结果表明,该方法在8:1压缩比下可获得大于40dB的峰值信噪比,同时有效地保护了光谱信息.     

一种干涉高光谱图像的3DSPIHT结合ROI压缩算法

 针对大孔径静态干涉成像光谱仪的成像特点,提出了一种基于三维小波变换的3DSPIHT算法结合ROI的图像压缩方案.对干涉高光谱图像序列进行了三维非对称离散小波变换.采用ROI方法对主要的光谱系数进行提升,以保护光谱信息.最后,对3DSPIHT算法进行改进,以有效编码干涉高光谱图像的小波变换系数.实验结果表明,该方法在8:1压缩比下可获得大于40 dB的峰值信噪比,同时有效地保护了光谱信息.     

一种大孔径静态干涉成像光谱仪高光谱图像的AT-3DSPIHT压缩算法

针对大孔径静态干涉成像光谱仪(LASIS)的成像特点,提出了一种支持感兴趣区域(ROI)的非对称三维分层树集划分(AT-3DSPI HT)压缩算法。首先,对高光谱干涉图像进行非对称三维离散小波变换。然后,根据光谱信息的分布特点,采用ROI方法对不同区域的变换系数赋予不同的编码精度,以保护光谱信息。最后,采用改进的三维分层树集划分(3DSPI HT)算法编码高光谱干涉图像的小波变换系数。实验结果表明,该方法在8:1压缩比下,获得大于40 dB的峰值信噪比,同时有效地保护了光谱信息。     

一种改进的无链表3DSPITH算法用于高光谱图像压缩

 针对大孔径静态干涉成像光谱仪(LASIS)的成像特点,提出了一种基于三维非对称等长树小波变换的无链表SPITH算法结合ROI的图像压缩方案。首先,对干涉高光谱图像进行三维非对称等长树离散小波变换。其次,采用ROI方法对主要的光谱系数进行保护。最后,采用改进的三维无链表SPITH算法,编码干涉高光谱图像的小波变换域。实验结果表明,该方法在8∶1压缩比下,获得大于40 dB的平均峰值信噪比,同时有效地保护了光谱信息。     

干涉多光谱图像压缩编码新技术

提出一种基于运动估计的三维小波变换和非对称零树编码的干涉多光谱图像压缩方案.该方案利用大孔径静态干涉成像光谱仪推扫成像特点,对图像进行分区域运动估计的三维小波变换.采用了一种新型非对称零树编码方法,该方法可在较少的图像间建立较长的零树,增加了系数编码时由重要结点变为不重要结点并趋于零的概率,使编码的效果更好.该方案消耗内存少,延时小,有利于卫星上的图像压缩,有效地保护了图像的光谱特性.在8倍压缩下,满足干涉多光谱图像的质量要求.     

基于分布式信源编码的干涉多光谱图像压缩

根据干涉多光谱图像的特点.提出一种基于分布式信源编码的干涉多光谱图像压缩箅法.干涉多光谱图像序列的相邻图像之间具有明显的平移特性,编码端通过块匹配算法检测出相邻帧间的相对位移量,联合块匹配算法估计的边信息帧进行比特平面码率估计,采用基于率失真提升的感兴趣区域编码,调整图像不同区域的率失真斜率来进行更合理的码率分配.实验结果表明.该算法比传统算法更好地保护了多光谱图像的光谱信息,在不同压缩比的情况下.满足卫星干涉多光谱图像压缩系统要求.易于硬件实现,更适于星上环境的应用.     

基于运动估计和ROI编码的干涉多光谱图像压缩

根据干涉多光谱图像的谱间相关性和光谱分布特点,提出一种基于运动估计和感兴趣区域编码的干涉多光谱图像压缩方法.为了去除多光谱图像的谱间相关性,采用运动估计法,对补偿后的图像(即预测误差)进行小波变换及率失真优化截取内嵌码块编码.同时采用率失真斜率提升的感兴趣区域编码方法,更好地保护光谱信息,使图像在相同的光谱分辨率下具有更好的空间分辨率.实验结果与基于三维小波变换的压缩方法以及比特平面移位的感兴趣区域编码方法相比,本文所提方法能有效改善恢复图像质量,提高编码效率,更好地保护光谱信息.     

提升小波变换与分形相结合的图像压缩

提出了一种提升小波变换与分形相结合的图像压缩方案.充分利用小波变换后系数能量的分布特性,对提升小波变换后的低频部分采用改进的分形图像压缩编码,其余部分采用集合分裂嵌入块(SPECK)编码算法.试验结果表明,该方法在提高了压缩效率的同时,获得了较高的恢复图像质量.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.