检索结果-内蒙古大学图书馆

Optical measurement systems for Industrial Inspection VI

作者： Plattner, Markus P. Brand, C.N. Mair, T. Schupfer, S. Buck, T.C. Koch, A.W. Technische Universität München Institute for Measurement Systems and Sensor Technology Theresienstr. 90 80333 Munich Germany

ISBN: (纸本)9780819476722

Within this work, we describe our newly developed interrogation scheme for fiber optic sensing applications. This measurement system will be utilized in Ariane launchers for monitoring temperature and mechanical stress distribution during flight. The acquired sensing data can be used to control propulsion unit an thrusters and thereby adapt the flight path in a way that damage on the launcher is prevented. In order to detect the peak wavelength of e.g. fiber Bragg grating (FBG) sensors, a tunable laser source based on a modulated-grating laser diode is able to scan through a more than 40nm wide spectrum in the infrared region. Several sensors with different spectral answers can be placed inside one sensor fiber and then interrogated sequentially. The magnitudes of the reflected intensities depend on the actual sensor position that is determined by the measurand (e.g. temperature). One single sensor is scanned by a variable number of spectral sampling points and the spectral answer of the sensor is then calculated by centroid algorithms. Depending an the spectral width of one sensor, the number of sensors that shall be interrogated and the required sampling points per sensor, a maximum sampling frequency of 240kHz is achievable with our hardware. Contrary to comparable systems, our interrogator is capable of switching to any available wavelength of its spectrum within a couple of nanoseconds. Therefore standard continuous sweeping through the entire spectrum is not necessary. This results in a new measurement scheme, wherein spectral gaps between consecutive sensors do not need to be scanned and can be skipped. Since most of the spectrum consists of the gaps between the sensors, overall measurement time is thereby reduced significantly. One problem arises from this measurement scheme: Due to the fact that the sensor's spectral answers vary in time, a special algorithm for tracking the spectral movement has to be implemented. The scope of this work is the description,

关键词： Fiber Bragg gratings

来源：评论

学校读者我要写书评

暂无评论

Thin film interferometer using a light source with spectrally non-equidistantly distributed sampling points

Thin film interferometer using a light source with spectrall...

引用

Optical measurement systems for Industrial Inspection VI

作者： Hirth, Florian Dudeck, Sven Jakobi, Martin Gerhard, Detlef Koch, Alexander W. Technische Universitaet Muenchen Institute for Measurement Systems and Sensor Technology Theresienstrasse 90 80333 Munich Germany Siemens AG CT PP 4 Germany

ISBN: (纸本)9780819476722

Numerous processes, e.g. in semiconductor and optics producing industries require film thickness observation. These measuring systems depend on different working principles, e.g. spectral reflectometry or ellipsometry. The spectral reflectometry interrogation method can be evaluated by various algorithms depending on resolution and measuring range demanded. All methods require a broad spectral distribution of the light source in order to sample the signal sufficiently for parameter extraction. Spectral sampling is often realized using a spectroscope, which produces equidistant sampling points in frequency space. In contrast to conventional spectrally broad light sources, the one employed here emits several spectral lines, which are non-equidistantly distributed. It also introduces problems like variations of intensity in the output spectrum and narrow wavelength bands, in which the reflected spectrum can be investigated. Non-equidistant sampling points additionally imply problems in conventional analysis algorithms, e.g. a FFT anticipates equidistant sampling points. Narrow wavelength bands imply little information to interrogate at the same spectral resolution of the interrogator. Strong variations of intensity lead to high noise levels at wavelengths with low intensities. Therewith, accuracy, resolution and measuring range are limited. An interrogator based on a Hg-Ar light source, a fiber coupler and a commercial spectroscope is described in this work. Both, accuracy and measuring range, are investigated by simulation and are experimentally proven on a glass on silicon demonstrator. Introducing an advanced algorithm, uncertainties invoked by the source's spectral and intensity distribution are minimized and resolution as well as measuring range are increased. © 2009 SPIE.

关键词： Thin films

来源：评论

学校读者我要写书评

暂无评论

Experimental investigation of polarization rotation in twisted optical fibers

Experimental investigation of polarization rotation in twist...

引用

International Symposium on Optomechatronic Technologies, ISOT

作者： Hala J. El-Khozondar Mathias S. Muller Thorbjorn C. Buck Rifa J. El-Khozondar Alexander W. Koch Institute for Measurement Systems and Sensor Technology Technische Universitä t München Munich Germany Institute for Measurement Systems and Sensor Technology Technische Universitä t München Munich Munich Germany

The twist induced polarization rotation in birefringent optical fibers is well understood and has been treated in the late seventies. We recently derived a formulation of the polarization rotation in twisted optical fibers using a tensorial coupled mode approach, that, other than existing theories, employs a fixed reference frame. This is interesting for fiber sensing applications, where the perturbing effects onto the fiber, such as strains induced by embedding the fiber into a host material, are conventionally given in a fixed laboratory reference frame. Hence, the derived theory can easily be integrated into existing formulations in the laboratory reference frame. In this work we demonstrate the experimental verification of the derived *** mechanically twist an optical fiber using an automated test stand and recording the change in polarization. The results are in close agreement with the theory.

关键词： Optical fiber polarization Optical fibers Optical fiber theory Optical fiber testing Laboratories Birefringence Optical coupling Capacitive sensors Optical materials Automatic testing

来源：评论

学校读者我要写书评

暂无评论

Fiber Bragg grating-based acceleration sensor

Fiber Bragg grating-based acceleration sensor

引用

International Symposium on Optomechatronic Technologies, ISOT

作者： Mathias S. Muller Thorbjorn C. Buck Alexander W. Koch Institute of Measurement Systems and Sensor Technology Technische Universität München Munich Germany

We present the design process of a fiber Bragg grating based fiber-optic single-axis acceleration sensor with minimized crosstalk. Crosscoupling of non-directional accelerations is minimized by introducing a unique double-membrane fixture of the sensor's mass of inertia leading to an almost diagonal form of the sensors stiffness-matrix. The sensor's resonance frequency, the sensor's sensitivity towards the stiffness of the spring-mass system and the mass of inertia are calculated from an analytical model and are verified by FEM simulation of the sensor. A singleaxis sensor design yielding a resonance frequency of 6.0 kHz with a sensitivity of Deltalambda = 1 pm/g at a non resonant acceleration is proposed.

关键词： Acceleration Fiber gratings Bragg gratings sensor systems Resonance Accelerometers Optical fiber polarization Optical fiber sensors Resonant frequency Optical fibers

来源：评论

学校读者我要写书评

暂无评论

Impact of angle ranges on thickness resolution in thin film reflectometry

Impact of angle ranges on thickness resolution in thin film ...

引用

International Symposium on Optomechatronic Technologies, ISOT

作者： Florian Hirth Max Rossner Martin Jakobi Alexander W. Koch Institute of Measurement Systems and Sensor Technology Technische Universität München Munich Germany

Thin film reflectometry is a common way to monitor film thicknesses in numerous processes. Semiconductor and optics producing industries, e.g., require film thickness observation. Spectral reflectometry interrogation is one of several methods, which can be assessed by various algorithms depending on resolution and measuring range demands. Incident angle is a crucial parameter to these interrogation methods. Light, under different incident angles, produces different spectral reflectivity functions. These are integrated by a detector, in this case a spectrograph. Therefore, one needs to minimize the range of incident angles onto the measured object in order to increase the resolution of film thickness. Lateral resolution may also be a crucial parameter in some processes. Lateral resolution is a function of the range of incident angle, it increases with increasing angle range. These two crucial facts result in an estimate of measuring error introduced by the angle range under a given maximal lateral resolution. A measuring setup for a range of incident angle measurements is presented, as well as an example interrogation of a thin film under different incident angles.

关键词： Transistors Reflectometry Optical films Semiconductor thin films Semiconductor films Goniometers Monitoring Reflectivity Detectors Thickness measurement

来源：评论

学校读者我要写书评

暂无评论

Comparison of different peak detection algorithms with regards to spectrometic fiber Bragg grating interrogation systems

Comparison of different peak detection algorithms with regar...

引用

International Symposium on Optomechatronic Technologies, ISOT

作者： Thomas Bodendorfer Mathias S. Muller Florian Hirth Alexander W. Koch Institute of Measurement Systems and Sensor Technology Technische Universität München Munich Germany

The resolution of many optical measurement systems employing ID or 2D array sensors (e.g. CCD-cameras) is limited by the pixel-resolution of the detector. Subpixel algorithms allow to exceed this limit. This paper aims at fiber Bragg grating interrogators, which acquire the sensor signal spectrometrically. The accuracy of measurement of these systems is strongly depending on the used algorithms. Five different algorithms for peak detection are described and compared in theory and experiment. Most of these algorithms can be found both in literature and in different software-libraries (e.g. MATLAB, LabVIEW...) To compare the different algorithms, a single fiber Bragg grating sensor was used to acquire data with a spectrometric measurement system consisting of a lD-CCD-line-array, a superluminescent light source and a reflection grating. The same data was fed the five algorithms, such that the output signals are comparable. To characterize the peak-search algorithms the standard deviation of the output data has been computed for different frame rates and variable wide regions of interest around a FBG-peak. As a result we can provida a concise recommendation which of the analyzed algorithms is suitable for an application in spectrometric fiber Bragg grating interrogators.

关键词： Detection algorithms Spectroscopy sensor arrays Optical sensors Optical arrays sensor systems Fiber gratings Bragg gratings Signal resolution Detectors

来源：评论

学校读者我要写书评

暂无评论

An extrinsic Fabry-Perot interferometric optical fiber sensor system for hydrogen detection

An extrinsic Fabry-Perot interferometric optical fiber senso...

引用

20th International Conference on Optical Fibre sensors

作者： Yang, Zhen Zhang, Min Lei, Ming Yu, Xiujuan Liao, Yanbiao Lai, Shurong Tian, Qian Li, Qisheng Zhang, Yi Zhuang, Zhi State Key Laboratory of Precision Measurement Technology and Instruments Tsinghua University Beijing China Optical Fiber Sensor Lab Dept. of Electronic Engineering Tsinghua University Beijing China Institute of Systems Engineering CAEP Mianyang Sichuan China

ISBN: (纸本)9780819478146

An extrinsic Fabry-Perot interferometric (EFPI) optical fiber hydrogen sensor based on palladium silver (Pd-Ag) film is designed for hydrogen leakage detection. The sensing mechanism of such a sensor is based on the mechanical stress that is induced in the Pd-Ag film when it absorbs hydrogen. The sensor system which is portable and suitable for field detection is formed by a conventional coupler, a low-power LED operating at 850 nm, and a high resolution miniature spectrometer. To obtain the absolute length of the EFPI air gap, a cross-correlation signal processing method is *** sensor is suitable for monitoring concentrations of hydrogen below the lower explosive limit. © 2009 SPIE.

关键词： Binary alloys

来源：评论

学校读者我要写书评

暂无评论

A modified cross-correlation method for white-light optical fiber extrinsic Fabry-Perot interferometric hydrogen sensors

A modified cross-correlation method for white-light optical ...

引用

2009 International Conference on Optical Instruments and technology, OIT'09

作者： Yang, Zhen Zhang, Min Liao, Yanbiao Lai, Shurong Tian, Qian Li, Qisheng Zhang, Yi Zhuang, Zhi State Key Laboratory of Precision Measurement Technology and Instruments Tsinghua University Beijing China Optical Fiber Sensor Lab Dept. of Electronic Engineering Tsinghua University Beijing China Institute of Systems Engineering CAEP Mianyang Sichuan China

ISBN: (纸本)9780819478948

An extrinsic Fabry-Perot interferometric (EFPI) optical fiber hydrogen sensor based on palladium silver (Pd-Ag) film is designed for hydrogen leakage detection. A modified cross correlation signal processing method for an optical fiber EFPI hydrogen sensor is *** the applying of a special correlating factor which advises the effect on the fringe visibility of the gap length and wavelength, the cross correlation method has a high accuracy which is insensitive to light source power drift or changes in attenuation in the fiber, and the segment search method is employed to reduce computation and demodulating speed is fast. The Fabry-Perot gap length resolution of better than 0.2nm is achieved in a certain concentration of hydrogen. © 2009 SPIE.

关键词： Optical fibers

来源：评论

学校读者我要写书评

暂无评论

A basic study of ultrasonic shear wave elastography in tissue-mimicking phantoms

A basic study of ultrasonic shear wave elastography in tissu...

引用

IEEE International Workshop on Medical measurement and Applications (MEMEA)

作者： V. Rengaraju A.F.F. da Silva I. Sack Ch. Kargel Institute for Measurement and Automation Division of Sensor Technology and Measurement Systems Bundeswehr University of Munich Neubiberg Germany Department of Radiology Charité Universitatsmedizin Berlin Campus Mitte Berlin Germany

Since many diseases cause changes in the mechanical properties of soft tissues, it is of interest to image their elasticity. Detection of tumors in early stages is challenging but paramount for the proper treatment of patients and thus to reduce the mortality rate. Elasticity imaging (elastography) has great potential to improve tumor diagnosis and is being developed and tested by several research groups with ultrasound and magnetic resonance imaging (MRI). As opposed to MRI, medical ultrasound is widely available, much more cost-effective and most of all a real-time imaging modality. In this paper we evaluate ultrasonic shear wave elastography, a dynamic approach to determine soft tissue properties. Our feasibility study using tissue-mimicking phantoms demonstrates that low frequency shear wave oscillation amplitudes in the micrometer range can be measured using commercial ultrasound scanners in combination with a particular signal processing method. Stiff tissue regions (tumors) show smaller shear wave amplitudes than the surrounding normal tissue. Not only can the examination time be reduced from about 10-20 minutes (MRI) to a few seconds, it may also soon be possible to detect certain cardiovascular dysfunctions in real-time using ultrasonic shear wave elastography.

关键词： Imaging phantoms Magnetic resonance imaging Ultrasonic imaging Neoplasms Biological tissues Elasticity Diseases Mechanical factors Medical treatment Testing

来源：评论

学校读者我要写书评

暂无评论

FRICTION IDENTIFICATION AND COMPENSATION ON NANOMETER SCALE

引用

IFAC Proceedings Volumes 2008年第2期41卷 2014-2019页

作者： A. Amthor T. Hausotte Ch. Ament P. Li G. Jaeger Institute of Automation and Systems Engineering Technische Universität Ilmenau Germany Institute of Process Measurement and Sensor Technology Technische Universität Ilmenau Germany

This work concerns the modelling and experimental verification of the highly nonlinear friction behavior in positioning on the nanometer scale. The main goal of this work is to adjust and identify a simple dynamic friction model which allows a model-based estimation of the friction force in combination with the system inertia against displacement. Experiments in the pre-sliding and sliding friction regimes are conducted on an experimental setup. A hybrid two-stage parameter estimation algorithm is used to fit the model parameters based on the experimental data. Finally, the identified friction model is utilized as a model-based feedforward controller combined with a classical feedback controller to compensate the nonlinear friction force and reduce tracking errors.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：