Improving the specularity of magnetic mirrors for atoms

An array of anti-parallel current-carrying wires creates an inhomogeneous magnetic field capable of reflecting neutral atoms. We present analytical and numerical analyses of the magnetic field produced by such an array, and describe methods for reducing the resulting rms angular deviation from specular reflection to less than 0.1 mrad. Careful choice of cross-sectional wire profiles is shown to dramatically improve specularity of reflection close to the surface. Additionally, we find that the specularity depends on whether the number of wires in the mirror is even or odd, and that there exists an optimal turning height above the surface that maximizes the specularity of reflection from the mirror. Received 16 November 1998     

Color-neutral switchable mirrors based on magnesium-titanium thin films

In an investigation of smart-window applications of switchable mirror thin films, Pd-capped magnesium-titanium thin films were prepared by dc magnetron sputtering. Their optical properties, switching durability and crystalline structures have been investigated. We show that Pd/Mg-Ti thin films with specific thicknesses are completely color-neutral in the transparent state and their optical switching properties are suitable for building and automobile window glass applications. The ternary hydrides of Mg_(1-x)Ti_x thin films with Pd overlayers are identified by in situ X-ray diffraction measurements during a hydrogen gas loading of 4%. Pd/Mg_(1-x)Ti_x thin film switchable mirrors show fast hydriding and dehydriding kinetics as compared to a Pd-capped pure Mg thin film due to the catalytic role of doped metallic Ti. PACS 75.20.En; 78.20.-e; 78.70.Ck; 42.70.-a     

Laser beam shaping with magnetic fluid-based liquid deformable mirrors

A new controllable laser beam shaping technique is demonstrated, where a magnetic fluid-based liquid deformable mirror is proposed to redistribute the laser phase profile and thus change the propagation property of the beam. The mirror is driven by an inner miniature actuator array along with a large outer actuator. The inner actuator array is used for deforming the magnetic fluid surface, while the outer actuator is used to linearize the fluid surface response and amplify the magnitude of the deflection. In comparison to other laser beam shaping techniques, this technique offers the advantages such as simplicity, low cost, large shape deformation, and high adaptability. Based on a fabricated prototype of the liquid deformable mirror, an experimental AO system was set up to produce a desired conical surface shape that shaped the incident beam into a Bessel beam. The experimental results show the effectiveness of the proposed technique for laser beam shaping.     

Effects of a magnetic field on the optical properties of dielectric mirrors

We have measured the changes in the polarization state of a monochromatic (λ=514.5 nm) light beam on reflection at normal incidence by a multilayer dielectric mirror placed in a time-modulated magnetic field. The dominant effect is a Faraday rotationΦ?3.7×10^?10 rad/G. The sensitivity (around 40Hz) obtained is \( \simeq 6 \times 10^{ - 9} {\text{ rad/}}\sqrt {{\text{Hz}}} \) which is dominated by the shot-noise limit (100 mW of light power).     

In situ magnetic hysteresis measurement of magnetic tips in magnetic force microscope

In situ magnetic hysteresis measurements of magnetic tips in a magnetic force microscope (MFM) are demonstrated using alternating gradient force magnetometry. The measured magnetic moments of MFM tips are estimated in the range from 10⁻⁶ to 10⁻⁵ emu by this technique and the whole MFM tips in cantilevers are considered to be measured from the value of measured magnetic moments. The relationship between the magnetic hysteresis loops of MFM tips and those of coated magnetic films is discussed.     

基于TLD算法的加油锥套跟踪

针对自主空中加油对接阶段锥套跟踪问题,提出了一种基于tracking learning detection (TLD)的锥套跟踪算法。该算法将加油锥套的跟踪任务分解成跟踪、学习、检测3个部分。跟踪模块在LK光流法的基础上添加跟踪失败自检测,筛选出好的跟踪点,跟踪加油锥套;检测模块构建级联分类器,对滑动窗遍历得到的图像块进行分类并返回含有目标的图像块,融合跟踪模块的跟踪框,给出最终跟踪结果;学习模块引入P N约束修正错误样本并学习更新检测模块。利用Creator/Vega Prime软件对空中加油进行视景仿真,在视景仿真视频上测试锥套跟踪算法。结果表明:TLD算法跟踪加油锥套成功率达95.5%,处理每帧平均耗时31.4 ms,能够满足加油锥套跟踪鲁棒性、准确率、实时性的要求。     

Optimization of a data storage system based on the array of ferromagnetic particles and magnetic force microscope

Optimal parameters for a data storage system based on ferromagnetic particles and magnetic force microscope (MFM) are calculated. The conditions necessary for data recording, storing, and reading are analyzed in the frame of a simple model of a spherical MFM probe and an array of spherical single-domain particles. The ultimate data densities in such a system are estimated.     

Reflectrons with ion orthogonal acceleration based on planar gridless mirrors

The feasibility of using structurally simple gridless electrostatic ion mirrors with a 2D field distribution in high-resolution time-of-flight (TOF) mass reflectrons is studied by numerical simulation. The configuration of a mirror with two control potentials providing third-order TOF focusing on energy and small TOF aberrations on spatial coordinates of the ion bunch is described.     

基于跟踪度的Gabor小波特征跟踪方法的研究

图像的边缘包含了目标的大量特征信息。利用Gabor小波可以从目标图像中提取具有特征位置、角度和尺度的参数。利用这些参数可以重建除均值以外的所有图像信息。图像边缘与均值无关。根据重建图像边缘线段的长度和边缘拟和度以及特征点的个数,提出了跟踪度的概念,分析了跟踪度的性质,并在跟踪度准则指导下确定了跟踪的特征点个数。仿真实验证明,跟踪度反映了目标特征跟踪的可靠程度,提供了跟踪精度的客观标准,为选择特征点个数、平衡计算复杂度和跟踪精度提供了客观的依据。通过对目标进行姿态变换和大面积遮挡的跟踪实验证明,当跟踪度达到0 95以上时就可以稳定地跟踪目标。     

Object tracking based on two-dimensional PCA

In this paper, we present a novel object tracking method based on two-dimensional PCA. The low quality of images and the changes of the object appearance are very challenging for the object tracking. The representation of the training features is usually used to solve these challenges. Two-dimensional PCA (2DPCA) based on the image covariance matrix is constructed directly using the original image matrices. An appearance model is presented and its likelihood estimation has been established based on 2DPCA representation in this paper. Compared with the state-of-the-art methods, our method has higher reliability and real-time property. The performances of the proposed tracking method are quantitatively and qualitatively shown in experiments.     

基于多级微反射镜的傅里叶变换红外光谱仪衍射效应分析

对基于多级微反射镜的傅里叶变换红外光谱仪的衍射效应进行了计算分析,讨论了多级微反射镜宽度,衍射距离以及波长产生的衍射效应对光谱复原的影响。从模拟的结果可知,在衍射距离小于10 cm,反射面宽度大于0.5 mm的情况下,衍射效应较小,而且探索出了一种可以减小噪声的数据处理方法。文章的结论将应用于微型傅里叶变换红外光谱仪的设计、数据处理以及系统的优化。     

Multiple spectral window mirrors based on Fibonacci chains of dielectric layers

The unique properties of one-dimensional (1D) Fibonacci chains of dielectric layers are experimentally demonstrated and exploited for the design of new mirrors with multiple reflection spectral windows. The new mirror structures are simple, straightforward to make and enable a wide variety of multiple spectral window device performance to be achieved. By changing the thickness of the layers or the order of the Fibonacci chain, tens or even hundreds of windows can be obtained with the same approximate reflectivity over a very broad spectral region. These mirrors have numerous applications in photonics and optoelectronics.     

Probe--sample coupling in the magnetic resonance force microscope

The magnetic resonance force microscope (MRFM) provides a route to achieving scanned probe magnetic resonance imaging with extremely high spatial resolution. Achieving this capability will require understanding the force exerted on a microscopic magnetic probe by a spatially extended sample over which the probe is scanned. Here we present a detailed analysis of this interaction between probe and sample. We focus on understanding the situation where the micromagnet mounted on the mechanical resonator generates a very inhomogeneous magnetic field and is scanned over a sample with at least one spatial dimension much larger than that of the micromagnet. This situation differs quite significantly from the conditions under which most MRFM experiments have been carried out where the sample is mounted on the mechanical resonator and placed in a rather weak magnetic field gradient. In addition to the concept of a sensitive slice (the spatial region where the magnetic resonance condition is met) it is valuable to map the forces exerted on the probe by spins at various locations; this leads to the concept of the force slice (the region in which spins exert force on the resonator). Results of this analysis, obtained both analytically and numerically, will be qualitatively compared with an initial experimental finding from an EPR-MRFM experiment carried out on DPPH at 4 K.     

Atomic force microscope tracking observation of Chinese hamster ovary cell mitosis

CHO cells possess easily identifiable karyotypes, and CHO cell chromosomes are large and few in number, making these cells ideal for mutational and drug toxicity studies and suitable for investigations of animal chromosome structure. Here, we used atomic force microscopy (AFM) in the tapping mode for detailed visualizations of Chinese hamster ovary (CHO) cell chromosomes during various mitotic phases, including typical prophase, prometaphase, metaphase, anaphase and telophase. Based on our detailed observations, we were able to divide metaphase and anaphase into sub-phases: metaphase I, II and III, and anaphase I and II. Furthermore, we used the AFM error-signal mode to visualize chromosomal ultrastructures and cytokinesis. While these visualizations were all successful, we found that the image quality was affected by cellular debris, contamination. Collectively, our results show that the AFM technique has great potential for the detailed study of chromosomes and chromosomal ultrastructures during all phases of the cell cycle, but that careful standards of sample preparation must be maintained.     

A microscope system based on bevel-axial method auto-focus

A microscope system based on bevel-axial method auto-focus (BAM-AFS) is proposed. The purpose is to establish an auto-focus microscope system that calculates the focus position one or many times. In this paper, we propose a bevel-axial method that had an included angle between CCD sensor and image plane with multi-parameters fusing from image to obtain the in-focus position directly in the first phase and combined Kalman estimate to obtain the in-focus position for different objects in the second phase. We discuss the relation between focus positions and image focus at the end.     

Scanning electro-optic microscope based on surface plasmon resonance

An optical scanning probe microscope, based on surface plasmon resonance (SPR) in the attenuated total reflection geometry, is shown to successfully image the polarization structures in self-assembled monolayers of hemicyanine adsorbed on a gold surface. Application of an ac field to the tip gives rise to the linear electro-optic effect in the monolayer just below the tip and the local change in the refractive index of the monolayer was detected via the ac component of the reflected light intensity, in which SPR-based detection intensifies the ac component. Polarization structures in a monolayer can be clearly imaged by this technique.     

Scanning probe microscope based on matter-wave surface trap

In order to scan nanostructures on a surface, we present a new recurrence tracking microscope based on an atomic trap. An evanescent wave trap is formed by the total internal reflection of two laser fields having different signs of detuning and penetration depths into the vacuum. The microscope employs the quantum recurrence phenomena of trapped atoms. Recurrence times depend on the initial energy of the wave packet in the trap and vary following the nanostructures on the surface under investigation.     

Axisymmetric eigenmodes of magnetic type in an open resonator with spherical mirrors

We develop a rigorous mathematical model describing axisymmetric eigenmodes of magnetic type of open resonators with spherical mirrors. On the assumption that the spectrum of complex eigenfrequencies of an open resonator exists, it is proved that this spectrum is discrete and has finite multiplicity with a single accumulation point at infinity. Theoretical analysis of the spectral characteristics of an open resonator is performed in the case where the wavelength is comparable with the resonator sizes. The limits of applicability of the well-known asymptotic models of open resonators are established. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 9, pp. 787–798, September 2006.     

基于人机工程学的光学显微镜机械结构设计

为研究出更合理的光学显微镜机械结构设计原理及相关规范,基于人机工程学的设计理念,参阅我国光学显微镜的相关规范,对金相显微镜的机械结构——载物台、调焦装置、物镜转换器等的设计进行了分析。从安全可靠和舒适经济的角度,提出了适合金相显微镜机械结构的人性化设计方法和原则。该设计原则和机械结构设计尺寸的计算公式具有普遍适用性。