应用CS理论实现同步采样压缩成像

为了减轻图像数据存储负担,实现图像在网络上的快速传输和实时处理,对一种新的压缩传感(CS)理论进行了研究。介绍了压缩传感理论的主要思想和基于压缩传感理论的光学成像系统,给出了一种新型图像重建算法—和谐正交匹配追踪算法,并进行了相应的模拟实验。实验结果显示,该成像机制可同步完成图像的采样与数据压缩,同时可获得良好的图像重建效果。由于该方法所要传输的信号数据量较小,所以十分有利于远距离的图像传输。     

基于复合抖动技术的三维轮廓数据压缩方法

三维扫描技术获取的三维轮廓数据体积较大,不便于三维数字博物馆数据的实时传输和显示。针对这个问题,提出了基于复合抖动技术的三维轮廓数据压缩方法。首先,利用虚拟结构光投影系统实现三维轮廓数据的图像存储。然后,对图像的不同通道使用不同的抖动技术进行处理,并将结果保存到8位灰度图中主要的3位或者3幅1位逻辑图中,实现三维轮廓数据的进一步压缩存储。实验表明,与提供的三维模型格式相比提出方法的数据压缩比高达75.9∶1,非常适合三维轮廓数据的实时传输、重建与显示。     

交通监控视频压缩与网络传输系统设计

针对现有交通监控视频中采用的H.264算法复杂度高、运算量大、误码跨帧传播等问题,提出了基于专用编解码芯片ADV212硬件实现JPEG2000标准的视频压缩传输系统的设计方法。设计以ADV7180对PAL制式模拟视频进行采集,以ADV212完成对采集后视频数据的压缩处理,最后通过DM9000A实现对压缩数据的以太网传输。FPGA作为系统主控,主要实现对各芯片的初始化及逻辑控制。实验结果表明,在保证压缩图像具有较高峰值信噪比的情况下,系统对速率为166Mbps的视频图像进行压缩处理后输出速率为8Mbps,有效减轻了网络传输带宽压力,且便于网络终端进行视频数据存储。同时系统还具有集成度高、体积小、性价比高、压缩比可调等优点,支持多种视频监控场合使用。     

光谱信息数据压缩方法—二真值线性预测法

本文针对线性预测压缩存在的游长短、压缩比低、恢复精度差等问题,提出了一种新的压缩方法—“二真值线性预测法”,其特点是恢复精度高、压缩比大、算法简捷、实时性好,适用于可由线性逼近表示的测量过程的实时压缩。经对典型光谱数据压缩实验表明,平均游长一般比线性预测压缩高1倍,在压缩恢复过程中可保留光谱特征信息,在1%恢复精度时,压缩后数据未编码的情况下一般可获得大于2:1的压缩比,编码后可获得4:1～5:1的压缩比。     

凸面光栅成像光谱仪图像数据实时压缩技术

凸面光栅成像光谱仪图像数据量巨大,给数据的传输和存储带来了压力,因此要对图像数据进行实时压缩。首先根据成像原理对图像数据的特点进行了分析,得出去除空间相关性和谱间相关性的压缩途径;然后,进行了压缩算法分析,提出了在谱间进行一阶线性预测、谱内进行JPEG2000压缩的三维压缩方案;最后,设计了基于FPGA+ADV212的实时压缩系统,其中FPGA用于逻辑控制和预测算法实现,ADV212用于JPEG2000压缩。分析结果表明:该系统具备无损和有损压缩能力,能够实现图像数据实时压缩。     

适用于楔形滤光片型光谱成像仪的快速无损数据压缩方法

楔形滤光片型光谱成像仪具有无运动部件、低光机复杂度等优点，是低成本微型化光谱成像仪的一个重要发展方向。不同于传统色散型光谱成像仪，楔形滤光片型光谱成像仪获取的数据是光谱-空间混合调制的图像。针对直接应用CCSDS123进行楔形滤光片型光谱成像仪数据压缩时压缩比较低的问题，结合楔形滤光片型光谱成像仪“谱像混合”、“推扫成谱”的特点，通过定义新的局部差向量，构建了一种低运算复杂度适合硬件实现的快速无损压缩方法WCCSDS123。新的局部差向量中参与计算的像元集合代表的是同一被观测点的光谱信息。WCCSDS123方法首先利用局部和与改进的局部差向量对采样点的值进行预测，再利用预测值与真实值计算预测残差并对其进行整数映射，最后采用采样自适应熵编码对映射预测残差进行编码完成压缩。在6组楔形滤光片型光谱成像仪数据上分别采用WCCSDS123和CCSDS123进行了压缩实验。实验结果表明，与CCSDS123相比，WCCSDS123的压缩比提高了约21.62%，压缩耗时没有明显差异。因此，该方法在提高压缩比同时，继承了CCSDS123复杂度低，易于硬件实现的优点。该方法WCCSDS123具有较低的计算复杂度，能够更加有效地利用空间光谱冗余信息，获得更好的压缩效果，是针对楔形滤光片型光谱成像仪的一种良好的快速无损数据压缩方法。     

分组Karhun-Loeve变换/整数小波变换高光谱影像准无损压缩新方法

提出了分组Karhunen-Leove变换(KLT)和整数小波变换(IWT)的高光谱图像数据压缩方法,并采用整数小波变换技术和Set Partitioning in Hierarchical Trees(SPIHT)压缩编码,实现了对分组Karhun-Loeve变换后的数据压缩。该压缩编码方法与现有压缩方法相比,既保留了Karhun-Loeve变换压缩性能和整数小波变换高压缩比的特点,也宜于实时传输。实验结果表明,分组Karhun-Loeve变换/整数小波变换/SPIHT在相同压缩比下,峰值信噪比比Karhun-Loeve变换/小波变换/WSFCVQ、Karhun-Loeve变换/小波变换/改进的对块零树编码压缩和Karhun-Loeve变换/WT/FSVQ分别提高了6 dB,9 dB和8 dB,运算时间减少一半,整体压缩性能有了较大的提高。     

改进的对块零树编码压缩方法对超光谱数据压缩

提出了对块零树的预测二值标量量化压缩编码方法，给出了压缩比公式，并应用此压缩编码实现了对超细光谱数据的压缩，该压缩编码方法既具有小波零树压缩编码高压缩比和宜于实时实现的特点，同时具有编码，解码速度快和易于实时传输等优点，实验结果表明，改进的对块零树编码压缩（IBBZTC）方法在不传输剩余误差的情况下，达到190倍的压缩比时，峰值信噪比仍然在30dB以上，压缩性能优于KL变换－静止图像压缩（KLT－JPEG），小波变换－矢量量化（WT－VQ），小波变换一零树矢量量化（WT－ZTVQ）和对块零树编码压缩方法。     

基于分割的热图压缩

热图作为一种专用图像，为了更好地传输和存储，必须进行压缩。本文依据热图的高频成分少，灰度较集中的特点，在借鉴模式识别思想的基础上，提出一种新的压缩方法——基于分割的热图压缩方法。该方法结合了小波变换编码与Ｒ－Ｃ分割方法对热图进行了压缩，并以传热学原理为依据，对其进行内插重建，获得了１０２４的高压缩比，并得到较好的可视性。这种方法尤其适用于仅具有目标和背景的红外热图。该方法有利于硬件的实现，且可以更好地利用硬件的实时性。     

适于星上应用的高光谱图像无损压缩算法

针对常见基于预测、变换、矢量量化及其组合的高光谱无损压缩算法压缩比低、压缩算法整体耗时以及硬件实现困难的问题,提出一种适于星上应用的高光谱图像无损压缩算法。首先,沿光谱线的第一谱段图像采用中值预测器进行谱段内预测,其他谱段图像采用谱间预测。谱间预测采用两步双向预测算法,第一步预测采用双向二阶预测器得到参考预测值,第二步预测采用本文提出的改进LUT搜索预测算法得出4个LUT预测值,然后将参考预测值与其比较得出最终的预测值。最后,使用XX-X空间高光谱相机的压缩系统试验设备对该文提出的压缩算法进行了试验验证。结果表明,压缩系统能快速稳定地工作,平均压缩比达到3.05 bpp,与传统方法相比,平均压缩比提高了0.14~2.94 bpp。有效的提高了高光谱图像无损压缩比和解决了压缩算法整体实现困难的问题。     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

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.     

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.