流式细胞仪中压电扫描振镜的设计

针对流式细胞成像的应用需求,设计了一维压电扫描振镜并进行了性能测试.该振镜利用微铰链梁将压电片的伸缩振动转化为反射面的旋转振动.首先,通过有限元仿真对压电振镜进行结构建模和性能分析,得到了振镜的工作模态以及扫描频率和最大扫描角度随结构尺寸的变化关系.接着,制备了由压电片和硅片基底组成的振镜样机.最后,利用角度测量系统对振镜的扫描特性和频响特性进行了测试.实验结果表明:2 mm×2 mm的反射面在12Vpp的电压驱动下可在谐振频率10.034 k Hz处产生14°的扫描角度,在5.2Vpp的电压驱动21.26 k Hz的高频谐振下,仍可以产生3.35°的扫描角度.振镜样机Q值达865,扫描角度与驱动电压幅值呈线性关系.该振镜具有较大的镜面尺寸和较高的扫描频率,可满足流式细胞扫描成像快速和高分辨率的应用需求.     

AFM扫描图像重构算法的改进

针对原子力显微镜（AFM）纳米成像中存在的失真问题,研究了通过探针建模实现AFM扫描图像重构方法.目前探针盲建模算法在重构AFM图像时存在较大误差,因此提出基于探针模型预估计的AFM扫描图像重构方法.该方法采用分区探针针尖建模,并通过基于该探针模型的反卷积运算实现AFM扫描图像重构,获得比较接近真实形貌的AFM扫描图像.文中介绍了算法的具体步骤,通过仿真和实验结果证明,该方法能够有效降低AFM图像重构时引入的误差,得到的图像更能反映样品表面真实的形貌.     

瓦斯突出煤体的纳米结构研究方法

提出了一种研究瓦斯突出煤体的纳米结构的新方法,介绍了用原子力显微镜(AFM)对煤矿石进行扫描并得到高精度微观图像的实验过程.该方法基于AFM的纳米级分辨率,可清晰观测到煤的裂隙、孔隙等显微构造.除了显示煤样的纳米结构,AFM还可对样品成像进行多角度分析,用于煤中瓦斯气体的含量测定和煤层气的开发,以及瓦斯吸附机理和煤的微观特性的研究.     

AFM轻敲模式下扫描参数对成像质量影响的研究

针对原子力显微镜(AFM)扫描参数对成像质量的影响规律,对现有的扫描参数影响成像质量的研究进行了分析。提出了以幅值误差作为评价AFM成像质量的指标,通过实验研究了扫描参数对AFM成像质量的耦合影响。发现了扫描频率fs、积分增益I和幅值设定点S这3个扫描参数间相互影响的现象,在S低较低情况下可设置更大的fs和I,在获取高质量成像的同时,提升了测量效率,对扫描参数的合理设置提供了可靠的操作准则。     

基于预压水激波管的压力传感器动态校准实验研究

针对目前国内水下冲击波压力传感器校准方法存在的缺陷,提出了一种基于预压水激波管的压力传感器动态校准实验方法.分析了预压水激波管比对式动态校准原理,研究了传感器动态特性影响因素,基于所组建的标准压力监测系统对水下冲击波压力传感器进行了动态校准实验,并采用傅里叶变换法得出了水下冲击波压力传感器的动态特性.实验结果表明,基于预压水激波管的压力传感器动态校准实验方法可以有效地对压力传感器进行动态校准并准确地获取其动态特性.     

优化型多扫描方式原子力显微镜的研制

本文提出和发展了一种多扫描方式的新型原子力显微镜(AFM)技术及系统。该系统拥有三个不同的扫描器,以相互组合的方式实现三种不同的扫描方式,由管状压电陶瓷驱动的柔性结构扫描器,采用样品扫描方式,对于小尺寸样品能够提供高分辨率的快速扫描;由叠层式压电陶瓷驱动的扫描器,采用探针扫描方式,提供各类样品的大范围扫描;由步进电机驱动的扫描器,采用样品扫描方式,能够实现大尺寸样品的大范围扫描。三种方式的单幅图像扫描范围可分别达到4μm×4μm、20μm×20μm、40μm×40μm。实验结果表明,借助于上述多扫描方式及独特的结构设计,该 AFM 不仅具有分辨率高、扫描速度快、重复性好等优化性能,而且能同时实现各类尺寸样品的各种扫描范围的微纳米成像,具有更好的实用性,可望在微纳米技术领域获得广泛应用。     

基于迭代学习控制的材料黏弹性纳米测量

原子力显微镜（AFM）是进行纳米材料力学特性（如材料黏弹性）测量的重要工具．压电陶瓷驱动器作为AFM的核心部件，由于其迟滞和蠕变特性的影响，致使在材料黏弹性纳米测量过程中，不仅测量速度慢，而且测量误差较大．为了解决以上问题，提出一种基于逆的迭代学习控制方法．通过在频域内学习系统的动态特性，补偿AFM的z轴动态误差，从而实现AFM系统的快速准确定位．该方法不仅避免了复杂的AFM系统建模过程，而且提高了系统输出时期望输入的跟踪精度．用美国DI公司的纳米原位测量仪对聚二甲基硅氧烷（PDMS）的纳米黏弹性进行了测量，验证了算法的适用性和有效性．     

原子力显微镜图像降噪与平面校正的同步实现

将小波阈值收缩去噪技术应用于原子力显微镜(AFM)图像去噪的同时,应用最小二乘拟合法对AFM二维小波分解近似子图像的一次倾斜平面进行校正,从而同步实现了AFM图像去噪与平面校正.在保证图像去噪效果及平面校正质量的前提下,大幅度减少了最小二乘拟合计算量,提高了算法实时性能.由于该方法借助于小波变换实现,可以方便地与图像的小波压缩方法相结合,因此更有利于AFM扫描图像的原位分析与处理.通过实验,采用上述方法对AFM扫描图像进行了降噪与平面校正处理,证明了此方法的有效性.     

O.92PZN-0.08PT晶体的缺陷与畴结构研究

应用环境扫描电子显微术(ESEM)、原子力扫描显微术(AFM)、同步辐射白光形貌术(SRWBT)等形貌成像技术研究了0.92PZN-0.08PT晶体的表面缺陷形态与铁电畴结构.通过对畴结构动态演化的同步辐射形貌观察,可揭示出该晶体的结构相变过程.     

基于纳米运动平台的原子力显微镜开发

采用一种无耦合、三轴精确定位的纳米运动平台作为扫描器,研制了一种新型原子力显微镜(AFM).该AFM有效消除了通常使用的单管式压电陶瓷扫描器扫描过程中运动耦合产生的两种结构误差--交叉耦合误差和扫描范围误差,极大提高了纳米测量及操作的精度.     

Atomic imaging of macroscopic surface conductivity

Scanning tunneling microscopy (STM) enables direct imaging of surface-state bands, through which electrical conduction occurs, confirmed by direct measurements with the four-point probe method. STM images also exhibit voltage drops along a surface due to electrical resistance of the surface states (scanning tunneling potentiometry). Scanning micro-four-point probes and multi-tip STM are newborn techniques for much more direct mapping of the conductivity. Such capability of imaging provides direct insights on carrier scattering at atomic scales.     

Broadband holography applied to eddy current imaging by using signals with multiplied phases

In this paper an eddy current imaging method for nondestructive testing purposes is presented which utilizes the concept of broadband holography. An eddy current coil which is used simultaneously as an antenna for eddy current generation and as a probe for detection of response of interaction between eddy currents and flaws, respectively, is moved along a synthetic aperture during the imaging procedure generating synthetic eddy current pulses by scanning a certain frequency range. In terms of wave propagation phenomena the penetration depth (range) of eddy currents in conducting media is small compared to the equivalent wavelength of this type of fields. Therefore, adequate resolution can only be obtained in the reconstructed cross-sectional images by phase multiplication of received multifrequency signals, which is equivalent to a fictitious reduction of wavelengths. Experimental results verify the imaging capability of this method with improved resolution compared to conventional eddy current testing methods.     

High-resolution terahertz reflective imaging and image restoration

We present a high-resolution terahertz (THz) reflective imaging system, operating at 2.52 THz, that employs a continuous-wave THz gas laser and a pyroelectric detector. The spatial resolution was evaluated from the system's modulation transfer function and tested by scanning a series of resolution targets. To further improve the image quality, Lucy-Richardson method was adopted to restore the scanning result. With the scanning spot profile measured using knife edge method, a satisfying restoration result can be obtained. Finally, the system's performance was observed by imaging some different test objects.     

Spiral scanning method for atomic force microscopy

A spiral scanning method is proposed for atomic force microscopy with thoroughgoing analysis and implementation. Comparing with the traditional line-by-line scanning method, the spiral scanning method demonstrates higher imaging speed, minor image distortion, and lower acceleration, which can damage the piezoelectric scanner. Employing the spiral scanning method to replace the line-by-line scanning method, the experiment shows that the time to complete an imaging cycle can be reduced from 800 s to 314 s without sacrificing the image resolution.     

High speed data collection system for magnetic field imaging by CTtechnique

A method of high-speed data collection used in imaging the magnetic-field distribution leaking from magnetic devices along any plane is proposed. The method uses the computed tomography (CT) technique. A high-speed data collection system developed for demonstrating the method is described. An image of the magnetic field is reconstructed from projection data provided by the voltage induced in the sensors of a line conductor and a rectangular coil moving in the plane of observation. Rotational scanning of the sensors is used for collecting the projections so that data-acquisition time can be reduced. To demonstrate the performance of the system, the reconstructed images of the magnetic-field distributions made by some permanent magnets are shown     

Phase retrieval from diffraction intensities by use of a scanning slit aperture

A noniterative method of retrieving the phase of a wave field from intensities measured during scanning of a slit aperture is proposed. In the measurements, one records the diffraction intensities of wave fields transmitted through a slit that is scanned along two directions in the Fresnel-zone plane of an object's field. From these intensities, the phase in the Fresnel-zone plane can be retrieved by a method in which a novel phase calculation technique that uses Fourier transforms is included. Because the method does not require lens systems, it provides a potentially useful means for coherent imaging by use of x rays, electrons, or nuclear particles.     

Three-dimensional sensing based on a dynamically focused laser optical feedback imaging technique

A new method analogous to three-dimensional confocally based sensing is proposed. This method uses the technique of laser optical feedback imaging, which takes advantage of the resonant sensitivity of a short-cavity laser to frequency-shifted optical feedback for highly sensitive detection, making it ideal for surface and volume measurements of noncooperative targets. Rapid depth scanning is made possible by use of an electrically controlled variable-focus lens. The system is able to detect height discontinuities, and because detection occurs along the axis of projection the system does not have problems of shadow. Preliminary results for a depth range of 15 mm and a resolution of 100 mum are presented.     

平面螺旋声阵列近场旋转扫描全息成像研究

针对一平面螺旋阵列在噪声源成像应用,分析了波束形成方法在低频段噪声成像能力的局限性,采用等效源法实现了对低频噪声的全息成像。为提高近程声全息成像性能,本文提出并采用不规则平面阵进行旋转扫描测量,重点研究了无参考传感器条件下对扫描数据的相位处理方法,实现了不同时刻测量数据的相位同步,利用仿真研究验证了该方法的有效性和优越性,并通过实际实验进行验证,对450Hz以下频率噪声的成像能力有显著提高。该方法测试条件要求低,测试结果可靠,相关结论具有参考价值。     

High-resolution full-field optical coherence microscopy using a Mirau interferometer for the quantitative imaging of biological cells

In this paper quantitative imaging of biological cells using high-resolution full-field optical coherence microscopy (FF-OCM) is reported. The FF-OCM was realized using a swept-source system, a Mirau interferometer, and a CCD camera (a two-dimensional detection unit). A Mirau-interferometric objective lens was used to generate the interferometric signal. The signal was analyzed by a Fourier analysis technique. Optically sectioned amplitude images and a quantitative phase map of biological cells such as onion skin and red blood cells (RBCs) are demonstrated. Further, the refractive index profile of the RBCs is also presented. For the 50× Mirau objective, the experimentally achieved axial and transverse resolution of the present system are 3.8 and 1.2 μm, respectively. The CCD provides parallel detection and measures enface images without X, Y, Z mechanical scanning.     

Electrochemical scanning tunneling microscope imaging of self-assembled monolayer of double-stranded DNA on Au(111)

Self-assembled monolayer of a double-stranded DNA, which was formed by a 20-nt 5'-thiol-modified oligonucleotide at the interface of Au(111)/solution, has been imaged and studied with electrochemical scanning tunneling microscopy (ECSTM). The results showed that the preferred directions of the adsorbed DNA were <110> and <112>. The measured width of the DNA stripes was 0.95 +/- 0.02 nm, which was consistent with the width of dsDNA base pairs. The contour of DNA in the STM image consisted of a series of blobs, which were due to the anchoring of the bases to the substrate along the dsDNA chain. The imaging of a large-scale array of DNA lying flat on the substrate offers a convenient method for the further application of high-resolution STM to the study of the interaction between DNA and a variety of molecules.