Weighted nonlinear correlation for controlled discrimination capability

We recently demonstrated the high discrimination capability as well as the high sensitivity to small intensity variations of the sliced orthogonal nonlinear generalized (SONG) correlation. This nonlinear correlation has a correlation matrix representation. Previous papers considered only the principal diagonal elements of the correlation matrix. We propose using the off-diagonal non-zero elements of the SONG correlation matrix in order to achieve variable discrimination performance and controlled detection adapted to the gray-scale variations. Moreover, we introduce negative coefficients in order to improve the discrimination properties of the SONG correlation. To control the degree of recognition we define a correlation that is related with the degree of degradation. The proposed changes to the SONG correlation may be implemented by means of optics.     

Pure phase correlator with photorefractive filter memory

We report on the investigation of a new compact configuration of an inverted VanderLugt-type correlator system. The phase of the Fourier transform of the image to be recognized is displayed on a phase-modulating electrically addressed spatial light modulator. This phase display is compared with the phase of the Fourier transforms of a reference library recorded in a photorefractive LiNbO(3) crystal. Angular hologram multiplexing permits fast data access, and the use of the conjugated replica of the stored templates leads to an elimination of phase distortions introduced by the optical system. With such a configuration, the correlator is fully shift invariant in spite of the photorefractive crystal thickness and has good discrimination with sharp correlation peaks.     

Video stabilization with sub-image phase correlation

A fast video stabilization method is presented,which consists of sub-image phase correlation based global motion estimation,Kalman filtering based motion smoothing and motion modification based compensation.Global motion is decided using phase correlation in four sub-images.Then,the motion vectors are accumulated to be Kalman filtered for smoothing.The ordinal motion compensation is applied to each frame with modification to prevent error propagation.Experimental results show that this stabilization system can remove unwanted translational jitter of video sequences and follow intentional scan at real-time speed.     

An improved long-term correlation tracking method with occlusion handling

By improving the long-term correlation tracking(LCT) algorithm, an effective object tracking method, improved LCT(ILCT), is proposed to address the issue of occlusion. If the object is judged being occluded by the designed criterion, which is based on the characteristic of response value curve, an added re-detector will perform re-detection, and the tracker is ordered to stop. Besides, a filtering and adoption strategy of re-detection results is given to choose the most reliable one for the re-initialization of the tracker. Extensive experiments are carried out under the conditions of occlusion, and the results demonstrate that ILCT outperforms some state-of-the-art methods in terms of accuracy and robustness.     

Millimeter wave carrier generation based on Brillouin fiber laser with improved tuning capability

An all-optically generated millimeter wave carrier at 21.7 GHz, 43 GHz and 64.45 GHz are experimentally achieved. These frequencies are realized by generating two consecutively laser wavelengths and are detecting on the 70 GHz high-speed photo detector (HSPD). The initial mixing between the Brillouin pump and the second-order Stokes wavelengths is spaced by 0.178 nm. This spacing, which is doubled from an inherently generated Stokes shift, is accomplished through an isolated circulation of the first order Stokes wave in the double Brillouin Stokes shifter (DSBS) built with 25-km single mode fiber. The generated millimeter carrier is measured at 21.7 GHz, 43 GHz and 64.4 GHz achieved with BP power of 11 mW, 30 mW and 47 mW, respectively.     

Sensible design of open-porous spherical architectures for hybrid supercapacitors with improved high-rate capability

Hybrid supercapacitors show high energy densities with good long-term cycling stability when used as energy sources. However, their poor rate performance as a consequence of their low ionic diffusion capability at high currents during cycling should be improved. Here, we propose using a spray-drying process to fabricate a novel structure comprising open-porous spherical lithium manganese oxide as an electrode material for hybrid supercapacitors. The resultant hybrid supercapacitor comprising full-cell systems shows a high specific capacitance (33.8 F cm⁻³ at a current of 1 A) and remarkable high-rate performance (25.6 F cm⁻³ at a current of 16 A). Moreover, outstanding cycling stability of 83% was attained at a current of 2 A after 5400 cycles. Our new strategy provides a useful methodology to increase the abundance of electrochemically active sites by fabricating a spherical structure using nanosized primary particles, which also leads to shorter diffusion pathways and to improved ionic electron transport because of the open-porous structure of the electrode materials.     

Input-image homogenization as a method to improve a correlator's discrimination capability

We propose an input-image preprocessing method consisting of homogenization of the image to improve the discrimination capability of a correlation-based recognition process. This method is an approximation of the optimal filter. It offers the advantage that correlation with the preprocessed images can easily be implemented in an optical correlator working with phase-only spatial light modulators.     

基于偏振鉴相的相干合成技术

推导了偏振相干合成后任意方向检偏的光强受束间相位差调制的解析表达式,并通过实验验证了表达式的正确性。开展了基于偏振鉴相的相干合成实验研究,用梯度下降算法锁定了两束激光的相位,获得了稳定的输出功率,验证了基于偏振鉴相的相干合成技术可行性;分析了基于偏振鉴相的相干合成技术的优点和对激光器的要求;提出了一种基于偏振鉴相的可定标放大全口径相干合成方法,采用多探测器和多级并行相位调制的方法,解决了随机并行梯度下降（SPGD）算法闭环带宽随合成光束数增加而快速退化的问题。     

An improved stair phase encoding method for absolute phase retrieval

An improved phase unwrapping method is proposed to reduce the projection fringes in three-dimensional (3D) surface measurement. Color fringe patterns are generated by encoding with sinusoidal fringe and stair phase fringe patterns in red and blue channels. These color fringe patterns are projected onto the tested objects and then captured by a color CCD camera. The recorded fringe patterns are separated into their RGB components. Two groups of four-step phase-shifting fringe patterns are obtained. One group of the stripes are four sinusoidal patterns, which are used to determine the wrapped phase. The other group of stripes are four sinusoidal patterns with the codeword embedded into stair phase, whose stair changes are perfectly aligned with the 2π discontinuities of sinusoidal fringe phase, which are used to determine the fringe order for the phase unwrapping. The experimental results are analyzed and compared with those of the method in Zheng and Da (2012. Opt Express 20(22):24139–24150). The results show that the proposed method needs only four fringe patterns while having less error. It can effectively reduce the number of projection fringes and improve the measuring speed.     

Interaural correlation discrimination: II. Relation to binaural unmasking

Many theoretical models of binaural interaction assume that sensitivity to interaural correlation underlies binaural unmasking. This paper explores the extent to which sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation measured directly in correlation discrimination experiments. The vehicle for this exploration is a simplified model of the underlying processes assumed by many models of binaural unmasking for the detection of narrow-band signals in the presence of broadband noise. Consideration is given to psychometric function slopes, detection thresholds, bandwidth effects, duration effects, level effects, and interaural-parameter effects. Although many of the results obtained from our analysis are consistent with the notion that the cue in binaural detection tasks is a change in interaural correlation, some significant inconsistencies are noted.     

基于改进的空域相关的多聚焦图像融合

提出了一种简单有效的像素级多聚焦图像融合方法。针对正交小波变换缺乏平移不变性而产生视觉失真的缺陷,采用Atrous算法将原图像分解在不同频率域上。Atrous算法先将滤波器h0(n),h1(n)各点间插入适当的零值后再与低频信号做卷积,故又称为"多孔算法"。将具有抑制噪声性能的空阈相关法作为高频子图像的融合规则,选取相关性强边缘特征显著的点作为最终融合子图像的像素点。实验表明,由此融合的图像能完好的保留边缘纹理信息。融合后的图像在客观评价和主管视觉效果上均有提高。     

134-W phase locking of two-dimensional four-fiber lasers with improved self-imaging resonator

We experimentally demonstrate the phase locking of a two-dimensional （2D） array of four fiber lasers using an improved self-imaging resonator with a spatial filter. The high visibility interference round stripes of the coherent beam profile are observed. The coherent output power of the fiber array exceeds 134 W. Tile entire system operates quite stably, and no thermal effects observe in the spatial filter, indicating that the coherent output power can be increased using this method.     

A correlation measure in non-equilibrium phase transitions

Bit-number cumulants of a probability distribution give ordered measures of correlations between subsystems. Especially the second one, the bit-number variance (which in equilibrium is connected with specific heat) is discussed with respect to its critical behaviour for special non-equilibrium phase transitions in chemical reaction systems. Also in non-equilibrium the critical behaviour indicates critical correlations.     

Interference analogy of Raman-luminescence problem and experimental discrimination by polarization correlation

Light scattering and luminescence under resonant optical excitation are shown to correspond to an interference fringe and broad background, respectively, in an optical interference experiment, if suitable definitions for the above two processes are adopted. It is proposed to discriminate between these two by a polarization measurement which is analogous to an interference experiment. The results of such an experiment in ZnSe and ZnTe are also reported.     

Transverse correlation vanishing due to phase aberrations

The concept of transverse correlation vanishing, between the fraction of power contained in the centre and wings of a probe beam, recently introduced [Opt. Commun. 282 (2009) 3854-3858] is important to be considered when measuring the effective focal length of any refractive index profile. When the latter is not parabolic it is shown that the transverse correlation could vanish, and this represents a potential source of error when measuring any lensing effect. We propose a low cost set-up (two photodiodes, a pinhole and a stop) able to reveal if the probe beam has monitored a pure or an aberrated lensing effect especially when it is time-dependent.     

Strong correlation to weak correlation phase transition in bilayer quantum Hall systems

At small layer separations, the ground state of a nu = 1 bilayer quantum Hall system exhibits spontaneous interlayer phase coherence. The evolution of this state with increasing layer separation d has been a matter of controversy. We report on small system exact diagonalization calculations which suggest that a single-phase transition, likely of first order, separates incompressible states with strong interlayer correlations from compressible states with weak interlayer correlations. We find a dependence of the phase boundary on d and interlayer tunneling amplitude that is in very good agreement with recent experiments.     

Quantum computational capability of a 2D valence bond solid phase

Quantum phases of naturally-occurring systems exhibit distinctive collective phenomena as manifestation of their many-body correlations, in contrast to our persistent technological challenge to engineer at will such strong correlations artificially. Here we show theoretically that quantum correlations exhibited in the 2D valence bond solid phase of a quantum antiferromagnet, modeled by Affleck, Kennedy, Lieb, and Tasaki (AKLT) as a precursor of spin liquids and topological orders, are sufficiently complex yet structured enough to simulate universal quantum computation when every single spin can be measured individually. This unveils that an intrinsic complexity of naturally-occurring 2D quantum systems—which has been a long-standing challenge for traditional computers—could be tamed as a computationally valuable resource, even if we are limited not to create newly entanglement during computation. Our constructive protocol leverages a novel way to herald the correlations suitable for deterministic quantum computation through a random sampling, and may be extensible to other ground states of various 2D valence bond phases beyond the AKLT state.     

用于PZT调制干涉仪的外触发式差动数字鉴相技术

基于相位测量的外差干涉系统以其信号处理方面的优势在光学计量领域得到了广泛的应用。介绍了采用机械调制方法的差动单频干涉系统的干涉信号小数级次的相位测量实现方法。针对机械调制干涉系统的信号有相位跃变点且周期不均匀的特点 ,提出了利用外触发信号对干涉信号进行整周期截取而后再鉴相的方法。研制了基于 FPGA的外触发式差动数字鉴相系统。实验测试表明 ,该鉴相系统在信号频率为 30 0 Hz～ 10 k Hz范围内达到的指标为 :示值稳定性优于± 0 .0 15°,极限偏差小于± 0 .0 7°