Shaping the Sensitive Volume of a Single-Sided NMR-Sensor to Profile Cylindrical Samples with High Resolution

This work reports the construction of a single-sided magnet generating a sensitive volume with adjustable curvature. It is useful to profile cylindrical samples with high depth resolution. The sensor geometry is based on the Profile NMR-MOUSE, which generates a parabolic field profile with a quadratic coefficient that decreases with the distance from the magnet surface. Such field profiles approximate cylinder walls within limited angular range with negligible deviation. Then, by varying the working depth, shells of different diameter in the sample can be matched. Simulation and experiments conducted on phantoms confirm that a depth resolution of about 35 μm can be obtained. The sensor was used to profile the structure of a cylindric air spring bellows with high resolution. Besides resolving the fiber layers used to reinforce the rubber matrix, the ingress of hexane was detected via T ₂ changes of the material.     

Two-dimensional imaging with a single-sided NMR probe

A new low field unilateral NMR sensor equipped with a two-dimensional gradient coil system was built. A new NMR-MOUSE concept using a simple bar magnet instead of the classical U-shaped geometry was used to produce magnetic field profiles comparatively homogeneous in extended lateral planes defining a suitable field of view for 2D spatial localization. Slice selection along the depth direction is obtained by means of the highly constant static magnetic field gradient produced by this magnet geometry. Implementing a two-dimensional phase-encoding imaging method 2D cross sections of objects were obtained with high spatial resolution. By retuning the probe it was possible to change the depth of the selected slice obtaining a 3D imaging method. The details of the construction of the new device are presented together with imaging tests to show the quality of space encoding.     

Single sided imaging sensor

A portable single sided sensor to render depth profiles of MR signal non-invasively is presented. The device utilizes a tailored permanent magnet array producing flat sensitive volumes up to 40 mm from the mobile inspection head. Automated slice selection is performed using a set of switched capacitors in the tuning and receiver circuits. A single channel spectrometer drives the multi-slice acquisition. The RF coil and magnet array geometries have been tailored to house gradient sets to further extend the image rendering capabilities for in-plane spatial resolution (2D and 3D MRI). The probe has been tested acquiring moisture profiles in concrete and porous rocks and measuring diffusion parameters on a phantom sample.     

基于银膜孔阵列超强透射效应的相敏表面等离子体共振传感器的仿真研究

A high spatial resolution, phase-sensitive Surface Plasmon Resonance（SPR） sensor based on Extraordinary Optical Transmission （EOT） is proposed to monitor the binding of organic and biological molecules to the silver surface. The 2D nanohole-array configuration is well suited ~br dense integration in a sensor chip. The optical geomeWy is collinear, which simplifies the alignment with respect to the traditional Kretschmann arrangement for SPR sensing. Various design parameters of the device have been studied by simulation. The heterodyne technique is used to improve the sensitivity. The optimization results indicate that the sensor has the advantages of achieving high resolution and a wide dynamic range simuhaneously.     

Spectral-mismatch-induced resolution limit of interferometric fiber Fabry-Perot sensor system

The mismatch of fiber Bragg gratings (FBGs) in spectral profiles can lead to a severe degraded resolution of the constructed fiber Fabry-Perot (FFP) sensor system through its effect on the fringe visibility. The variation of visibility induced by spectral mismatch and the corresponding phase resolution limit are analyzed theoretically and experimentally. Theoretical analyses are based on the approximation of Gaussian profiles to the reflection spectra of weak FBGs, especially with consideration of side lobes. The investigation provides an insight into the evolution of the fringe visibility caused by spectral mismatch, and shows good agreement with experimental results. An optimum phase resolution of about 55 μrad/Hz^1/2 above 100 Hz is achieved for a nearly 4 m-long FFP sensor by matching spectral profiles of the gratings and balancing path length differences of the tandem interferometers.     

Two-dimensional pressure measurements with nanosecond time resolution

An optical setup for the measurement of acoustic shock waves is demonstrated experimentally. This sensor, which is based on surface plasmon excitation, provides ns time resolution as well as 7m lateral resolution. Initial experiments with laser-induced plasma generation in a water cell already show that in a simple geometry high lateral resolution gives new insight into the ongoing processes.     

高分辨紫外电子轰击互补金属氧化物半导体器件的实验研究

基于真空紫外光电阴极和背照式互补金属氧化物半导体(CMOS)图像传感器研制了紫外光响应的电子轰击CMOS(EBCMOS)器件,实现了EBCMOS器件在40 mlx光照度环境下的高分辨探测,电子图像灰度随电子能量的变化呈现出极好的线性关系.对器件成像分辨率测试的结果表明,在电场强度为5000 V/mm时,器件的空间分辨率可以达到25 lp/mm,与国际相关报道水平相当.研制的EBCMOS器件可直接在紫外弱光探测领域应用,如天文观察、高能物理、遥感测绘等,同时也可为下一步研制可见光和近红外敏感的EBCMOS器件提供参考.     

Microfluidic sensor based on integrated optical hollow waveguides

A simple integrated optical refractometric sensor based on hollow-core antiresonant reflecting optical waveguides is proposed. The sensor uses the antiresonant reflecting guidance mechanism and permits one to measure the refractive index of a liquid filling the core by simply monitoring the transmitted spectrum. The device has been made with standard silicon technology, and the experimental results confirm numerical simulations performed in one- and two-dimensional geometry. The sensor exhibits a linear response over a wide measurement range (1.3330-1.4450) and a resolution of 9 x 10(-4) and requires a small analyte volume.     

Fiber-optic sensors for the estimation of oxygen gradients within biofilms on metals

This paper presents an optical approach to measure the oxygen gradients in biofilms grown on stainless-steel 316L. The sensor is constructed by immobilizing an oxygen-quenchable fluorophore at the tip of an optical fiber. The response time and reversibility of fiber-optic sensor have been analyzed. By mounting the optical fiber using a computerized micromanipulator, the vertical profiles of oxygen are measured with 10 μm depth resolution across biofilms on metal coupons. Steep concentration gradients of oxygen have been observed within the biofilm, both perpendicular and parallel to the metal surface. Optical response of the biofilm grown metal surface is found to be a consistent measure of the oxygen profiles within biofilms.     

Depth map resolution improvement for 3D range-intensity correlation laser imaging

This Letter proposes a high bit-depth coding method to improve depth map resolution and render it suitable to human-eye observation in 3D range-intensity correlation laser imaging. In this method, a high bit-depth CCD camera with a nanosecond-scaled gated intensifier is used as an image sensor; subsequently two high bit-depth gate images with specific range-intensity profiles are obtained to establish the gray depth map and finally the gray depth map is encoded by an equidensity pseudocolor. With this method, a color depth map is generated with higher range resolution. In our experimental work, the range resolution of the depth map is improved by a factor of 1.67.     

Computer simulation of heat distribution processes in W/(La,Ce)B<Subscript>6</Subscript>/W sensor of thermoelectric detector

The results are presented of the computer simulation of heat distribution in the W/(La,Ce)B₆/W multi-layer sensor of the thermoelectric detector after the absorption of single photons with the energies 1–100 eV. The influence of the choice of computer simulation parameters on the revealing of the peculiarities of heat transmission processes arising in the sensor of detector depending on the photon energy, the sensor geometry, the absorption area of the absorber surface and the depth of photon thermalization is investigated in details. The energy resolution and the count rate of sensor are evaluated. It is shown that the multi-layer sensor with the thermoelectric (La,Ce)B₆ is capable to register a single photon in a wide range of the electromagnetic spectrum at 0.5 K; it has an advantages as compared with the sensor based on the CeB₆ with the operating temperature 9 K, and has perspectives to be used in the science and technology.     

一种光纤EFPI高温传感器

提出了一种金属封装的光纤外腔式珐珀(EFPI)高温传感器。利用不同材料的不同热膨胀系数,使EFPI的腔长对温度变化敏感,可以应用在高温场合下。该传感器具有结构简单、灵敏度高、耐高温等特点,测试结果表明,灵敏度为0.3837μm/℃,线性度为0.9956,分辨率为0.26℃。它的正常工作温度范围为0-400℃。     

波长扫描法布里-泊罗光纤加速度计的研究

利用光纤传感器的独特优点 ,用波长扫描法将 Fabry- Perot干涉仪 (以下简称 FPI)和传统加速度计相结合 ,得到了较好的分辨率。分析了在 FPI中多光束干涉对双光束干涉的影响。实验研究表明 ,它对由振动引起的位移 (加速度 )变化相当灵敏     

Optical fiber long-period grating with solgel coating for gas sensor

The novel long-period fiber grating (LPFG) film sensor is composed of the long-period grating coated with solgel-derived sensitive films. The characteristics of the transmissivity of the LPFG film sensor are studied. By analyzing the relation among the sensitivity Sn, the thin film optical parameters, and the fiber grating parameters, the optimal design parameters of the LPFG film sensor are obtained. Data simulation shows that the resolution of the refractive index of this LPFG film sensor is predicted to be 10(-8). Experimentally, a LPFG film sensor for detection of C(2)H(5)OH was fabricated, and a preliminary gas-sensing test was performed.     

Investigation of the processes of heat propagation in W/FeSb<Subscript>2</Subscript>/W detection pixel of the single photon thermoelectric detector

The results are presented of the computer modeling of the processes of heat propagation in the single layer detection pixel of the thermoelectric single photon detector after the absorption of photon with the energy of 1–1000 eV. The different geometries of the detection pixel consisting of the tungsten absorber and thermoelectric sensor from the strongly correlated FeSb₂ semiconductor are considered. The differences of temporal dependence of the signal appearing on the sensor for various size of the sensitive pixel elements are studied in detail. The energy resolution and the count rate of the detector are estimated. It is shown that the FeSb₂ sensor of thermoelectric detector provides the generation of significantly higher signal as compared with the CeB₆ sensor and has the perspectives of application in the single photon detectors with the high energy resolution.     

Sub-nano resolution fiber-optic static strain sensor using a sideband interrogation technique

We propose a novel sideband interrogation technique with multiplex radio frequency intensity and phase modulation to measure the resonance frequency difference between two optical resonators. Based on this new technique, an ultrahighly sensitive fiber-optic static strain sensor system consisting of a pair of identical fiber Fabry-Perot interferometers is built by incorporating a cross-correlation data processing algorithm. A static strain resolution down to 0.8 nε is demonstrated experimentally, which makes the sensor system a useful tool for geophysical research applications.     

基于自适应频率不变响应基阵的宽带信号方位估计

提出一种设计频率不变响应基阵的自适应模拟方法，并将其用于构造波束形成矩阵来实现宽带信号的聚焦。该方法不仅保持了波束域方位估计算法的运算量小、分辨率高等优点，还具有相关信号子空间能解相关源的能力，且对阵形及各阵元的指向性也没有任何限制。仿真结果说明了本文方法的有效性。     

Surface structure monitoring with plastic optical fiber

A sensor was designed using a plastic optical fiber to study the potential of detecting structural deformities and corrosion of metallic surfaces, in particular for applications in constricted areas such as pipes. The principle of the sensor is based on the collection of scattered light reflected by the surface imperfections. Several types of metallic materials in various surface profiles and stages of corrosion have been studied. The sensor was able to determine the position of ridges on the surface and corroded regions in all cases evaluated in the study. A sensitivity of 100 mV/mm was detectable for proximity and a vertical resolution of 1 mm has been measured.     

兆线元EBCCD微光探测系统

研发了一种兆线元EBCCD微光探测系统。该系统采用了俄罗斯生产的电子轰击CCD传感器,该传感器为倒像式静电聚焦系统,CCD为背照式1000×1000像元,传输模式为帧传输。为了获得高质量的图像,采用了多重滤波、自动去背景噪声以及帧叠加的方法。该系统能在10-5lx照度条件下得到较好的视频信号。该系统具有很高的灵敏度和分辨力,与ICCD微光摄像机作了比较。结果表明,电子轰击CCD微光成像系统性能较为理想。     

一种新型光纤法布里-珀罗应变干涉仪

论述了一种非本征法布里 珀罗光纤应变传感器。采用透明弹性聚合物薄膜作为法布里 珀罗干涉腔,聚合物固定在多膜光纤末端作为应变敏感元件。传感器的分辨率为2μm,测量精度在0～5000μm范围内为5μm。