玻璃在线激光测厚误差的透反互补抑制

为了抑制激光在线测厚时入射角波动引起的误差,根据几何光学分析了激光透射式和反射式测厚原理,发现激光在特定入射角附近波动时,两种方式的测厚误差一正一负,具有互补性,在此基础上提出基于透射和反射同时测量的互补式测厚方法,该方法可将误差限定在透射式和反射式测量误差之间,抑制在线测厚误差.对于有机玻璃平板,理论计算表明,当激光入射角在67.013°±4°波动时,相对误差绝对值在1%以内,误差抑制率均值大于90%;当入射角为61.536°时,误差抑制率为100%.利用线结构激光器和两个线阵CCD相机搭建互补式测厚实验系统,测量了标称厚度为1~5mm的有机玻璃平板,与透射式和反射式测厚结果进行对照,除厚度为1mm的玻璃外,互补式测厚误差被限制在透射式和反射式之间,最大误差抑制率达61%.实验结果表明,该互补式方法有效抑制了误差,提高了在线厚度测量准确度,解决了在线测量不可重复性导致的无法通过均值法减小误差的问题.     

Accurate estimation of normal incidence absorption coefficients with confidence intervals using a scanning laser Doppler vibrometer

When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.     

Experimentally Determining Bloch Parameters of Hamiltonian for Single-Qubit Systems

By considering the identification problem of unknown but fixed Hamiltonian H = S0σ0 ＋∑i=x,y,z Siσi where σi （i = x, y, z） are pauli matrices and σ0=I, we explore the feasibility and limitation of empirically determining the Hamiltonian parameters for quantum systems under experimental conditions imposed by projective measurements and initialization procedures. It may be unsurprising to physicists that one can not obtain the knowledge of So no matter what kind of projective measurements and initialization are permitted, but the observation draws our attention to the importance of the parameter identifiability under different experimental condition. It has also been revealed that one can obtain the knowledge of ｜Sz｜ and Sx^2＋Sy^2 at most when only the projective measurement {｜0/（0｜, ｜1/（1｜} is permitted to perform on and initialize the qubit. Further more, we demonstrated that it is feasible to distinguish ｜Sx｜, ｜Sy｜, and ｜Sz｜ even without any a priori information about Hamiltonian if at least two kinds of projective measurement or initialization procedures are permitted. It should be emphasized that both projective measurements and initialization procedures play an important role in quantum system identification.     

Deterministic joint remote state preparation of arbitrary single- and two-qubit states

In this paper, two novel schemes for deterministic joint remote state preparation(JRSP) of arbitrary single- and twoqubit states are proposed. A set of ingenious four-particle partially entangled states are constructed to serve as the quantum channels. In our schemes, two senders and one receiver are involved. Participants collaborate with each other and perform projective measurements on their own particles under an elaborate measurement basis. Based on their measurement results,the receiver can reestablish the target state by means of appropriate local unitary operations deterministically. Unit success probability can be achieved independent of the channel's entanglement degree.     

Correcting movement errors in frequency-sweeping interferometry

Absolute distance measurements can be performed with an interferometric method that uses only a single tunable laser. This method has one major drawback, because a small target movement of the order of one wavelength during a measurement will be interpreted as a movement of one synthetic wavelength. This effect is usually mitigated by adding a second (nonscanning) laser. We show that absolute distance measurements can be performed with only one laser if the movements encountered are smooth, on the time scale of one measurement. In this case the movement errors can be compensated with a simple algorithm that combines several subsequent measurements. First experimental results show good agreement with theory.     

Patch nearfield acoustic holography combined with sound field separation technique applied to a non-free field

The conventional nearfield acoustic holography(NAH) is usually based on the assumption of free-field conditions, and it also requires that the measurement aperture should be larger than the actual source. This paper is to focus on the problem that neither of the above-mentioned requirements can be met, and to examine the feasibility of reconstructing the sound field radiated by partial source, based on double-layer pressure measurements made in a non-free field by using patch NAH combined with sound field separation technique. And also, the sensitivity of the reconstructed result to the measurement error is analyzed in detail. Two experiments involving two speakers in an exterior space and one speaker inside a car cabin are presented. The experimental results demonstrate that the patch NAH based on single-layer pressure measurement cannot obtain a satisfied result due to the influences of disturbing sources and reflections, while the patch NAH based on double-layer pressure measurements can successfully remove these influences and reconstruct the patch sound field effectively.     

Fringe projection profilometry based on complementary color-encoded fringe patterns

3D measurement techniques based on color-encoded fringe pattern projection have been widely used in various fields of engineering recently. There is one problem that the surface color of measured object may interfere with the color of projected fringe pattern. To solve this problem, a novel method based on complementary color-encoded fringe projection is proposed. Two color-encoded fringe patterns whose fringe colors are complementary are designed. The first pattern is with the sinusoidal fringe embedding into the green color channel which is used to evaluate phases by Fourier transform method. The fringe color of the captured image is established with the help of the complementary color fringe pattern, which is based on the feature of color complementation. Thus, the influence brought by the color of object surface can be eliminated, and decoding errors can be further reduced. Experiment results indicate that the proposed method is valid and can be applied to the measured colorful objects.     

Imaging a periodic moving/state-changed object with Hadamard-based computational ghost imaging

We propose a method for imaging a periodic moving/state-changed object based on computational ghost imaging with Hadamard speckle patterns and a slow bucket detector, named as PO-HCGI. In the scheme, speckle patterns are produced from a part of each row of a Hadamard matrix. Then, in each cycle, multiple speckle patterns are projected onto the periodic moving/state-changed object, and a bucket detector with a slow sampling rate records the total intensities reflected from the object as one measurement. With a series of measurements, the frames of the moving/state-changed object can be obtained directly by the second-order correlation function based on the Hadamard matrix and the corresponding bucket detector measurement results. The experimental and simulation results demonstrate the validity of the PO-HCGI. To the best of our knowledge, PO-HCGI is the first scheme that can image a fast periodic moving/state-changed object by computational ghost imaging with a slow bucket detector.     

Procedure for direct measurement of general quantum states using weak measurement

Recent work by Lundeen et al. [Nature (London) 474, 188 (2011)] directly measured the wave function by weakly measuring a variable followed by a normal (i.e., "strong") measurement of the complementary variable. We generalize this method to mixed states by considering the weak measurement of various products of these observables, thereby providing the density matrix an operational definition in terms of a procedure for its direct measurement. The method only requires measurements in two bases and can be performed in situ, determining the quantum state without destroying it.     

Complete ultrasonic transducer characterization and its use for models and measurements

Transmitting and receiving properties of ultrasonic piezoelectric crystal transducers that directly affect the measured output voltage in an ultrasonic measurement system are described. These transducer properties are the transducer's electrical impedance and sensitivity, the transducer's radiation impedance, and the transducer's effective parameters (effective radius and focal length). It is shown that all these properties can be obtained with a series of calibration measurements, most of them purely electrical in nature. This series of measurements is described, including a newly developed method that makes the determination of the transducer sensitivity simpler than with previous methods. It is demonstrated that by combining these transducer properties with knowledge of the electrical properties of the pulser/receiver and cabling and the acoustic/elastic processes present in an ultrasonic measurement system, it is possible to accurately simulate the output voltage of the system.     

Measurement of elastic constants of nematic liquid crystals with use of hybrid in-plane-switched cell

A new method for quick and pretty accurate measurements of splay, twist and bend elastic constants of nematic liquid crystals is experimentally verified. The main concept relies on exploiting only the electric field and determining magnitudes of nematic elastic constants from threshold fields for Freedericksz transitions in only one hybrid in-plane-switched cell. In such cell the deformations of an investigated liquid crystal are controlled by three separated pairs of electrodes confining measurement domains. In two of them inter-digital electrodes are mounted on one cell cover. Splay, twist and bend elastic constants can be measured by a proper choice of electrodes?? configuration together with orienting cover coatings (without applying magnetic fields). In this paper, we describe layout of our cells and results of experimental tests by using different liquid crystals: 5CB and 6CHBT (with positive dielectric anisotropy), Demus?? esters (with negative dielectric anisotropy) and new liquid crystals mixtures produced in our university.     

Measurement of femtosecond laser-induced damage and ablation thresholds in dielectrics

The paper is focused on the importance of accurate determination of surface damage/ablation threshold of a dielectric material irradiated with femtosecond laser pulses. We show that different damage characterization techniques and data treatment procedures from a single experiment provide complementary physical results characterizing laser–matter interaction. We thus compare and discuss two regression techniques, well adapted to the measurement of laser ablation threshold, and a statistical approach giving the laser damage threshold and further information concerning the deterministic character of femtosecond damage. These two measurements are crucial for laser micromachining processes and high peak-power laser technology in general.     

3-D shape measurement based on complementary Gray-code light

A combination of phase-shift with Gray-code light projection into a three-dimensional (3-D) measurement system has been exploited to digitalize 3-D shape information of a tested object, even with a discontinuous surface. Unfortunately, the phase unwrapping will fall into an error, when an improper value of Gray coding is caused by mistake at the partial boundary of two adjacent binary words. To this end, a new complementary Gray-code method is proposed in this paper as well as the corresponding phase-unwrapping method. This problem of phase unwrapping could be cleverly solved by projecting an additional Gray-code pattern to extend this code and using the different and complementary boundary locations of the traditional and additional codes. The results of computer simulation and experiment confirm that this proposed method based on complementary Gray-code can reliably reconstruct the nature phase distribution of the tested object with only one extra fringe pattern.     

微型数据采集器及其在加速器周围辐射场实时监测中的应用

各种类型加速器周围的辐射场变化是很复杂的, 只有对其进行连续的实时监测才能准确地掌握全面资料. 以往的数据采集系统用的是模拟信号长距离传输方式, 采集器体积较大, 存储技术上也显落后, 已不能适应当今的需求. 为辐射场实时监测研制的微型数据采集器采用了先进的设计理念, 具有体积小、通讯能力强、数据存储量大且断电数据不丢失的特点, 可运行于局域网环境. 它既可利用局域网远距离向控制计算机传递数据, 也可用便携式PC通过串口就近读取数据. 所以它不但适于固定场所的连续监测, 也可灵活地用于临时测量场所. 介绍了它的主要性能和在各类型加速器周围所做测量的结果.     

Retrieval of the vertical column of an atmospheric constituent from data fusion of remote sensing measurements

Techniques of data fusion are presently being considered with increasing interest for application to atmospheric observations from space because of their capability to optimally exploit the complementary information provided by different instruments operating aboard on-going and future satellite missions. The task of combining measurements of the same target, when carried out at the level of the retrieved state vectors, faces with two major problems: the need to interpolate the products represented on different retrieval grids which determines a loss of information and the presence of a priori information in the products that can determine a bias in the product of the data fusion. The measurement space solution method avoids these problems. Based on this method we present a novel approach to retrieve the vertical column of an atmospheric constituent from data fusion of remote sensing measurements. We apply the method to retrieve the ozone column from the fusion of simulated measurements of the IASI nadir-viewing spectrometer onboard the METOP-A platform and of the MIPAS limb sounder onboard the ENVISAT satellite. The performance of the method is evaluated in terms of retrieval errors and averaging kernels of the products. The results show the evidence of improved retrieval quality when comparing the outcome of data fusion with that of the inversion process applied to spectra from either of the two instruments.     

Quantum Dense Coding Without Joint Measurement

We propose two schemes for quantum dense coding without Bell states measurement. One is deterministic, the other is probabilistic. In the deterministic scheme, the initial entangled state will be not destructed. In the probabilistic scheme, the initial unknown nonmaximal entangled state will be transformed into a maximalentangled one. Our schemes require two auxiliary particles and perform single-qubit measurements on them. Thus our schemes are simple and economic.     

On the implication of Bell’s probability distribution and proposed experiments of quantum measurement

In derivating of Bell’s inequalities, the probability distribution is supposed to be a function only of a hidden variable. We point out that the true implication of the probability distribution of Bell’s correlation function is the distribution of joint measurement outcomes on the two sides. It is therefore a function of both the hidden variable and the settings. In this case, Bell’s inequalities fail. Our further analysis shows that Bell’s locality holds neither for dependent events nor for independent events. We think that the measurements of EPR pairs are dependent events, and hence violation of Bell’s inequalities cannot rule out the existence of local hidden variable. To explain the results of EPR-type experiments, we suppose that a polarization-entangled photon pair can be composed of two circularly or linearly polarized photons with correlated hidden variables, and a couple of experiments of quantum measurement are proposed. The first uses delayed measurement on one photon of the EPR pair to demonstrate directly whether measurement on the other could have any nonlocal influence on it. Then several experiments are suggested to reveal the components of the polarization-entangled photon pair. The last one uses successive polarization measurements on a pair of EPR photons to show that two photons with the same quantum state behave the same under the same measuring conditions.     

Electron Magnetic Moment in Highly Charged Ions: The ARTEMIS Experiment

The magnetic moment (g‐factor) of the electron is a fundamental quantity in physics that can be measured with high accuracy by spectroscopy in Penning traps. Its value has been predicted by theory, both for the case of the free (unbound) electron and for the electron bound in a highly charged ion. Precision measurements of the electron magnetic moment yield a stringent test of these predictions and can in turn be used for a determination of fundamental constants such as the fine structure constant or the atomic mass of the electron. For the bound‐electron magnetic‐moment measurement, two complementary approaches exist, one via the so‐called “continuous Stern–Gerlach effect”, applied to ions with zero‐spin nuclei, and one a spectroscopic approach, applied to ions with nonzero nuclear spin. Here, the latter approach is detailed, and an overview of the experiment and its status is given.     

The Characteristic Noise Connected with Continuous Measurement in Classical System without Memory

In the present paper we propose the way of passage from quantum theory of continuous measurements based on the Lindblad equation to its “classical” analog. The last one describes the influence of continuous measurement on the behavior of macroscopical Markov system. Such theory can be represented in the form of the Fokker-Planck equation for the distribution function of measured system. The diffusion tensor of this equation is uniquely determined by a type of the measured quantity. As the example of using of the approach proposed we describe the stationary states of linear dissipative systems induced by measurements in them. We consider possible qualitative effects connected with measurements also. In particular we demonstrate on the simple example, how in the macroscopic system, consisting of noninteracting parts, measurement of global integral of motion results in relaxation to the quasi-thermodynamic equilibrium between parts of the system. The “temperature” of such state is determined by the total energy of the system and by mean value of measured quantity.      

基于双面质点振速测量的声场分离技术

现有的声场分离技术或是基于双面声压测量或是基于单面声压和质点振速测量。本文以二维空间傅里叶变换法作为声场分离算法,提出一种基于双面质点振速测量的声场分离技术。论文首先推导出了该方法的理论模型,随后通过仿真研究验证了该方法的有效性,并通过与基于双面声压测量的声场分离方法的比较说明了其优越性。结果表明:采用基于双面质点振速测量的声场分离方法可以有效实现声场分离;基于双面质点振速测量的声场分离方法可以获得更高的质点振速分离精度,而基于双面声压测量的声场分离方法可以获得更高的声压分离精度。