To see the other types of publications on this topic, follow the link: Optical based sensor.
Dissertations / Theses on the topic 'Optical based sensor'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Optical based sensor.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bronk, Karen Srour. "Imaging based sensor arrays /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1996.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1996.Adviser: David R. Walt. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
2
Andrews, Jeffrey Pratt. "Longitudinal misalignment based strain sensor." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43283.
Full textAbstract:
A practical fiber optic strain sensor has been developed to measure strains in the range of 0.0 to 2.0 percent strain with a resolution ranging between 10 and 100 microstrain depending on sensor design choices. This intensity based sensor measures strain by monitoring strain induced longitudinal misalignment in a novel fiber interconnection. This interconnection is created by aligning fibers within a segment of hollow core fiber. Related splice loss mechanisms are investigated for their effect on resolution. The effect of gauge length and launch conditions are also investigated.
Master of Science
3
Chen, Qiao. "ESA based fiber optical humidity sensor." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/10134.
Full textAbstract:
Several techniques for measuring humidity are presented. The goal of the study is to use the electrostatic self-assembled monolayer synthesis process to fabricate a Fabry-Parot Cavity based optical fiber humidity sensor. The sensing scheme bases on the refractive index change with relative humidity of the film applied to the end of optical fiber. That is, the change in reflected optical power indicates certain humidity. To achieve this, some chemicals induce on specific coating materials were applied at the end of optical fiber. In this thesis, experimental results are given to prove that the humidity sensor has high sensitive and fast response time. Furthermore, we investigate the potential for the use of human breathing monitoring and air flow rate detection. Results from preliminary tests of each are given.Master of Science
4
Miller, Mark S. "Optical fiber-based corrosion sensor systems." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-03042009-041455/.
Full text
5
Fan, Chenjun. "Fiber optic sensor based on dual ring resonator system /." Online version of thesis, 1992. http://hdl.handle.net/1850/11070.
Full text
6
Sun, Kailiang. "Fluorescence based optical sensor for protein detection." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2010r/ksun.pdf.
Full text
7
Mohamad, Mohd Fuad Bin. "Luminescence-based optical sensors towards in vivo analysis." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31215.
Full textAbstract:
Continuous monitoring of physiological parameters such as pH and oxygen (O2) are of great importance in determining the health status of a patient. Arterial blood gas analysis is a current clinical method used to measure pH, PCO2, PO2, and the concentration of variety of ions, typically with blood withdrawn from an artery. The need for robust, and a rapidly responding technology to enable bed-side monitoring has driven considerable efforts to produce better sensor devices. Optical sensing systems have experienced rapid growth, with drivers including low-cost optical fibres, and the availability of miniature optical set-ups (light sources, detectors, etc.). Herein, polymer-based optical fibre sensors for pH and O2 sensing were developed. The pH and/or oxygen reporters were immobilised at the end of an optical fibre by photo-polymerisation, and their performance in measuring pH and O2 concentration investigated. pH sensing was based on fluorescence detection using single excitation/single emission (Chapter 2), and single excitation/dual emission (Chapter 3). O2 sensing was based on the luminescence quenching of metalloporphyrins by oxygen (Chapter 4). In the last chapter, the in vivo applicability of an O2 sensor was investigated by measuring O2 level changes inside an ex vivo lung.
8
Rooney, James Michael. "Model based exploration of an optical sensor architecture." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620014.
Full text
9
Xiao, Hai. "Self-Calibrated Interferometric/Intensity-Based Fiber Optic Pressure Sensors." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28845.
Full textAbstract:
To fulfill the objective of providing robust and reliable fiber optic pressure sensors capable of operating in harsh environments, this dissertation presents the detailed research work on the design, modeling, implementation, analysis, and performance evaluation of the novel fiber optic self-calibrated interferometric/intensity-based (SCIIB) pressure sensor system.
By self-referencing its two channels outputs, for the first time to our knowledge, the developed SCIIB technology can fully compensate for the fluctuation of source power and the variations of fiber losses. Based on the SCIIB principle, both multimode and single-mode fiber-based SCIIB sensor systems were designed and successfully implemented. To achieve all the potential advantages of the SCIIB technology, the novel controlled thermal bonding method was proposed, designed, and developed to fabricate high performance fiber optic Fabry-Perot sensor probes with excellent mechanical strength and temperature stability. Mathematical models of the sensor in response to the pressure and temperature are studied to provide a guideline for optimal design of the sensor probe. The solid and detailed noise analysis is also presented to provide a better understanding of the performance limitation of the SCIIB system. Based on the system noise analysis results, optimization measures are proposed to improve the system performance. Extensive experiments have also been conducted to systematically evaluate the performance of the instrumentation systems and the sensor probes. The major test results give us the confidence to believe that the development of the fiber optic SCIIB pressure sensor system provides a reliable pressure measurement tool capable of operating in high pressure, high temperature harsh environments.Ph. D.
10
Xu, Lina. "Optical fiber humidity sensor based on evanescent wave scattering." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07092004-112625/.
Full textAbstract:
An optical fiber humidity sensor has been devised using a porous sol-gel silica (PSGS) coating as a transducer. Evanescent wave scattering (EWS) in the PSGS coating. PSGS particles are highly hydrophilic and have a strong tendency to absorb water molecules from the surrounding environment. The absorbed water molecules form a thin layer on the inner surface of the pores inside the porous silica and enhance EWS, from which an indicatory signal can be obtained. The humidity sensor presented in this thesis has a fast response, is reversible, low cost, and has a broad dynamic relative humidity range from 3.6?0-6% to 100% or humidity range from 1.2ppm to 30000ppm. Because of its multiple advantages, including immunity to electromagnetic interference, resistance to corrosive environments, and high sensitivity, this humidity sensor has various applications. In soil moisture sensing, this humidity sensor can avoid the interference caused by compounds in soil water. For electrical transformer moisture sensing, this humidity sensor can avoid the effect of electromagnetic fields.
11
Qin, Zengguang. "Distributed Optical Fiber Vibration Sensor Based on Rayleigh Backscattering." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24105.
Full textAbstract:
This thesis includes studies of developing distributed optical fiber vibration sensor based on Rayleigh backscattering with broad frequency response range and high spatial resolution.
Distributed vibration sensor based on all-polarization-maintaining configurations of the phase-sensitive optical time domain reflectometry (OTDR) is developed to achieve high frequency response and spatial resolution. Signal fading and noise induced by polarization change can be mitigated via polarization-maintaining components. Pencil-break event is tested as a vibration source and the layout of the sensing fiber part is designed for real applications. The spatial resolution is 1m and the maximum distance between sensing fiber and vibration event is 18cm.
Wavelet denoising method is introduced to improve the performance of the distributed vibration sensor based on phase-sensitive OTDR in standard single-mode fiber. Noise can be reduced more effectively by thresholding the wavelet coefficient. Sub-meter spatial resolution is obtained with a detectable frequency up to 8 kHz.
A new distributed vibration sensor based on time-division multiplexing (TDM) scheme is also studied. A special probe waveform including a narrow pules and a quasi-continuous wave can combine the conventional phase-sensitive OTDR system and polarization diversity scheme together in one single-mode fiber without crosstalk. Position and frequency of the vibration can be determined by these two detection systems consecutively in different time slots. Vibration event up to 0.6 MHz is detected with 1m spatial resolution along a 680m single-mode sensing fiber.
Continuous wavelet transform (CWT) is investigated to study the non-stationary vibration events measured by our phase OTDR system. The CWT approach can access both frequency and time information of the vibration event simultaneously. Distributed vibration measurements of 500Hz and 500Hz to 1 kHz sweep events over 20 cm fiber length are demonstrated using a single-mode fiber.
Optical frequency-domain reflectometry (OFDR) for vibration sensing is proposed for the first time. The local Rayleigh backscatter spectrum shift in time sequence could be used to determine dynamic strain information at a specific position of the vibrated state with respect to that of the non-vibrated state. Measurable frequency range of 0-32 Hz with the spatial resolution of 10 cm is demonstrated along a 17 m fiber.
12
Glomon, Lhusak. "Source based chromatic methodology for optical fibre sensor systems." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400231.
Full text
13
Ren, Meiqi. "Distributed Optical Fiber Vibration Sensor Based on Phase-Sensitive Optical Time Domain Reflectometry." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34400.
Full textAbstract:
In this thesis, the work focuses on developing distributed optical fiber vibration sensors based on phase-sensitive optical time domain reflectometry (Φ-OTDR). Three works have been accomplished to improve the performances of Φ-OTDR for distributed vibration sensing. Firstly, Φ-OTDR based on a polarization diversity scheme is demonstrated to mitigate the polarization mismatch effect occurring in traditional systems. A theoretical analysis is performed in different polarization cases corresponding to coherent and polarization diversity detection. Φ-OTDR based polarization diversity shows a great potential in the multi-events sensing application. Two vibration events are simultaneously detected and their signal to noise ratios are improved by 10.9 dB and 8.65 dB, respectively, compared to the results obtained by a conventional coherent scheme.
Intensity fluctuation in a phase-sensitive optical-time domain reflectometry (Φ-OTDR) system caused by stochastic characteristics of Rayleigh backscattering has limited relative vibration strength measurement, which is proportional to dynamic strain. A trace-to-trace correlation coefficient is thus proposed to quantify the Φ-OTDR system stability and a novel approach of measuring the dynamic strain induced by various driving voltages of lead zicronate titanate (PZT) is demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of the fast Fourier transform spectra at fundamental frequency and high-order harmonics based on Bessel functions. Experimental results show high correlation coefficients and good stability of our Φ-OTDR system, as well as the small measurement uncertainty of measured peak values.
To reduce the intra-band noise caused by the finite extinction ratio of optical pulses, Φ-OTDR based on high extinction ratio generation is studied. Two methods are developed for achieving high extinction ratio of optical pulse generation. One of the approaches is to synchronize two cascaded electro-optic modulators to achieve high extinction ratio operation. The other one is to use the nonlinear optical fiber loop mirror as an optical switch to suppress the continuous wave portion of optical pulse. The sensing range of 1.8 km and 8.4 km with corresponding spatial resolution of 0.5 m and 2 m have been demonstrated based on cascaded two electro-optic modulators and nonlinear optical fiber loop mirror setup, respectively.
14
Chermak, Lounis. "Standalone and embedded stereo visual odometry based navigation solution." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9319.
Full textAbstract:
This thesis investigates techniques and designs an autonomous visual stereo based navigation sensor to improve stereo visual odometry for purpose of navigation in unknown environments. In particular, autonomous navigation in a space mission context which imposes challenging constraints on algorithm development and hardware requirements. For instance, Global Positioning System (GPS) is not available in this context. Thus, a solution for navigation cannot rely on similar external sources of information. Support to handle this problem is required with the conception of an intelligent perception-sensing device that provides precise outputs related to absolute and relative 6 degrees of freedom (DOF) positioning. This is achieved using only images from stereo calibrated cameras possibly coupled with an inertial measurement unit (IMU) while fulfilling real time processing requirements. Moreover, no prior knowledge about the environment is assumed. Robotic navigation has been the motivating research to investigate different and complementary areas such as stereovision, visual motion estimation, optimisation and data fusion. Several contributions have been made in these areas. Firstly, an efficient feature detection, stereo matching and feature tracking strategy based on Kanade-Lucas-Tomasi (KLT) feature tracker is proposed to form the base of the visual motion estimation. Secondly, in order to cope with extreme illumination changes, High dynamic range (HDR) imaging solution is investigated and a comparative assessment of feature tracking performance is conducted. Thirdly, a two views local bundle adjustment scheme based on trust region minimisation is proposed for precise visual motion estimation. Fourthly, a novel KLT feature tracker using IMU information is integrated into the visual odometry pipeline. Finally, a smart standalone stereo visual/IMU navigation sensor has been designed integrating an innovative combination of hardware as well as the novel software solutions proposed above. As a result of a balanced combination of hardware and software implementation, we achieved 5fps frame rate processing up to 750 initials features at a resolution of 1280x960. This is the highest reached resolution in real time for visual odometry applications to our knowledge. In addition visual odometry accuracy of our algorithm achieves the state of the art with less than 1% relative error in the estimated trajectories.
15
Tian, Xiaoyi. "Microwave Photonic Sensing Based on Optical Microresonators." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29545.
Full textAbstract:
Optical microresonators (OMRs) have been widely applied in various sensing applications. However, the sensing performances of conventional OMR-based sensors are subject to resonance parameters and fabrication accuracy and are further restricted by the interrogation scheme used. Recently, microwave photonic (MWP) techniques have been used to realize high-speed and high-resolution OMR-based sensors. So far, those MWP schemes are either still fabrication dependent or only applicable to specific uses, and rare attention has been paid to achieving multi-parameter sensing that is indispensable in real-life applications.
The thesis proposes novel OMR-based MWP sensing schemes with improved sensing performances. Based on the MWP sideband processing technique, a new MWP interrogation scheme, which features a high resolution regardless of the OMR parameters and fabrication imperfections, is proposed and demonstrated in the sensing of temperature, humidity, and magnetic field, respectively, with high sensitivity and high resolution, where an automatic correction mechanism is added to compensate for resonance lineshape variation automatically. Next, the high-resolution MWP sensing scheme is extended to cascaded OMRs to enable multi-parameter sensing capability. The simultaneous high-resolution MWP sensing of temperature and humidity with two cascaded OMRs is demonstrated. Lastly, machine learning (ML) and deep learning (DL) techniques are applied to MWP sensing to reduce the complexity further. The temperature-insensitive MWP humidity sensor is first achieved with the support vector regression. Then, a new MWP multi-parameter sensing paradigm with the least requirement on the OMR structure is proposed by incorporating DL to process the raw interrogation results directly. The simultaneous MWP sensing of temperature and humidity with a single optical resonance using the convolutional neural tangent kernel is demonstrated.
16
Wu, Nan. "Optical Frequency Domain Reflectometry Based Quasi-distributed High Temperature Sensor." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/76905.
Full textAbstract:
Temperature sensing in harsh environment is desired in many areas, such as coal gasification, aerospace, etc. Single crystal sapphire is an excellent candidate for construction of harsh environment sensors due to its superior mechanical and optical properties even at temperature beyond 1600°C. The temperature inside a coal gasifier can be as high as 1200°C. And there is dramatic temperature gradient between the inner and outer layers of the gasifier refractory. Previous work has been done at Virginia Tech's Center for Photonics Technology to design and fabricate a sapphire wafer based Fabry-Perot interferometer (FPI) sensor for temperature sensing in coal gasifiers. The sensor head is based on the use of sapphire wafer which is attached to a lead-in sapphire fiber to be applied in the ultrahigh temperature region; and the sapphire fiber is spliced to a multi-mode fused silica fiber for quality signal transmission in lower temperature areas. One of the challenges encountered by this approach is the shear force to the sapphire fiber, which is caused by the differential thermal expansion between the inner and outer layers of the gasifier refractory. This shear force may be so significant to break the sensor probe. This thesis proposed a free space based interrogation sensing system to address that problem. In this free space based interrogation sensing system, only the sensor head is placed in the inner refractory wall, while all the other parts of the system are placed in the outer refractory or outside the gasifier at the ambient room temperature. An optical frequency domain reflectometry (OFDR) based multiplexed technique is applied in the sensor design to realize temperature measurement at multiple locations along the optical path. In this work, three sapphire wafers based multiplexed temperature sensor is fabricated and calibrated in laboratory. This multiplexed high temperature sensor shows linear response in the range of 20°C ~ 1000°C, with a sensitivity of 1.602?10??/°C and a resolution of 1.3°C.Master of Science
17
Wu, Chujun. "Silicon-on-insulator based optical microring resonator sensor and improvement methods." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19894.
Full textAbstract:
Photonic sensing technologies offer unexceptionable features for taking high requirement measurement in a harsh environment. They inherit advantages such as fast speed and immunity from electromagnetic interference from optical communications. In addition, with the silicon-on-insulator (SOI) technologies, chip scale optical sensors are capable of providing high sensitivity with an ultra-compact form factor. The motivation is derived from the high demand for sensors in the new era of the Data Age and the great potential of fast response, highly sensitive and ultra-compact photonic sensor. Furthermore, rapid sensor development puts forward a new prospect for many areas such as medical and health measurement, defence technology, and the internet of things. With all the advantages that SOI-based chip scale optical sensors provide, there are still shortcomings can be improving to provided much more capable sensing abilities from many aspects. With that in mind, this thesis will focus on SOI-based optical microring resonator, one of the most popular SOI-based optical structure for sensing purpose; and solutions for two shortcomings of the common SOI-based optical sensor. One of the solutions that will be mentioned in this thesis is intended to solve the issues of limited measurement speed and low resolution that caused by the way of the data analysis in the common SOI-based optical sensing system. The second purposed solutions in this thesis focused on the connection schemes of the SOI-based optical sensor; Common connection schemes of SOI-based optical chip needs at least two optical ports for coupling the light into and out of the silicon photonics chip which limits the ability to perform measurements at remote locations that are hard to be reached. Chapter 4 and 5 of this thesis contains detailed explorations of these shortcomings and solutions. An integrated photonic sensor based on optoelectronic oscillator with an on-chip sensing probe that is capable of realising highly sensitive and high-resolution optical sensing is presented in this thesis as a solution for the first shortcoming. The key component is an integrated SOI-based microring resonator which is used to implement a microwave photonic bandpass filter (MPBF) to effectively suppress the side modes of the optoelectronic oscillator (OEO) by more than 30dB, thus generating a peak RF signal that maps the detected optical change into a resulting shift in the oscillating frequency. As an application example, the proposed optical sensor system is employed to detect small changes in temperature, and experimental results demonstrate a highly sensitive optical temperature sensor with an achieved sensitivity of 7.7 GHz/°C. Moreover, the proposed sensing system revealed a 0.02°C measurement resolution which is a tenfold improvement compared with the modest resolution of 0.23°C seen by the conventional MPBF system without the OEO loop, rendering it highly suitable for diverse high-resolution sensing applications. With the purpose of reducing the size of the SOI-based photonic sensor and to overcoming the second shortcoming, an ultra-compact, reflective optical sensor probe based on SOI microring resonator and Y-junction structure is also presented in this thesis. This structure is capable of simultaneously achieving high sensitivity and fine resolution optical sensing. The reflective configuration of the probe enables remote measurements at locations which are otherwise hard to be assessed by transmission based sensors. As an application example, the proposed sensor probe for temperature measurement is demonstrated. Experiment results show that the center wavelength shift of the sensor’s reflected spectrum offers a linear response to temperature change with a high sensitivity of 66 pm/°C.
18
Dey, Sanjoy Namuduri Kameswara. "Performance analysis of CCR based distributed sensor network based on optical wireless communication." A link to full text of this thesis in SOAR, 2008. http://hdl.handle.net/10057/2007.
Full textAbstract:
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering.Copyright 2008 by Sanjoy Dey. All Rights Reserved. Includes bibliographical references (leaves 16-18).
19
Xue, Ruipeng. "Nanofiber Based Optical Sensors for Oxygen Determination." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405508835.
Full text
20
McConney, Michael Edward. "Learning and applying material-based sensing lessons from nature." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29749.
Full textAbstract:
Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.Committee Chair: Tsukruk, Vladimir; Committee Member: Shofner, Meisha; Committee Member: Srinivasarao, Mohan; Committee Member: Thio, Yonathan; Committee Member: Weissburg, Marc. Part of the SMARTech Electronic Thesis and Dissertation Collection.
21
Garcia, Marisol. "TRULY NON INVASIVE GLUCOSE OPTICAL SENSOR BASED ON METAL NANOPARTICLES GENERATION." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2260.
Full textAbstract:
Diabetes is a disease that causes many complications in human normal function. This disease represents the sixth-leading cause of death in USA. Prevention of diabetes-related complications can be accomplished through tight control of glucose levels in blood. In the last decades many different glucose sensors have been developed, however, none of them are really non invasive. Herein, we present the study of the application of gold and silver nanoparticles with different shapes and aspect ratios to detect glucose traces in human fluids such as tears and sweat. This is to our knowledge the first truly non invasive glucose optical sensor, with extraordinary limit of detection and selectivity. The best proven nanoparticles for this application were gold nanospheres. Gold nanospheres were synthesized using chloroauric acid tri-hydrated (HAuCl4.3H2O) in solution, in the presence of glucose and ammonia hydroxide. The higher the glucose concentration, the higher the number of nanoparticles generated, thus the higher the extinction efficiency of the solution. The linear dependence of the extinction efficiency of the gold nanoparticles solution with glucose concentration makes of this new sensor suitable for direct applications in biomedical sensing. Our approach is based on the well known Tollens test.M.S.
Department of Chemistry
Arts and Sciences
Industrial Chemistry
22
Bang, Hyungseok. "INTEGRATED OPTICAL SPR (SURFACE PLASMON RESONANCE) SENSOR BASED ON OPTOELECTRONIC PLATFORM." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3289.
Full textAbstract:
Current major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic functionality poses requirements to the senor head; the sensor head needs to have reasonably small size while it should have reasonable sensitivity and fabrication tolerance. This research proposes a novel type of SPR sensor head and demonstrates a fabricated device with an array of integrated optical SPR sensor heads endowed with optoelectronic functionality. The novel integrated optical SPR sensor head relies on mode conversion efficiency for its operational principle. The beauty of this type of sensor head is it can produce clear contrast in SPR spectrum with a highly miniaturized and simple structure, in contrast to several-millimeter-scale conventional absorption type or interferometer type sensor heads. The integrated optical SPR sensor with optoelectronic functionality has been realized by structuring a dielectric waveguide based SPR sensor head on a photodetector-integrated semiconductor substrate. A large number of unit sensors have been fabricated on a substrate with a batch fabrication process, which promises a high throughput SPR sensor system or low-priced disposable sensors.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
23
Aspey, Robin Andrew. "A wavelength encoded optical current sensor based on chromatic modulation techniques." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399286.
Full text
24
Asebedo, Antonio Ray. "Development of sensor-based nitrogen recommendation algorithms for cereal crops." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19229.
Full textAbstract:
Doctor of PhilosophyDepartment of Agronomy
David B. Mengel
Nitrogen (N) management is one of the most recognizable components of farming both within and outside the world of agriculture. Interest over the past decade has greatly increased in improving N management systems in corn (Zea mays) and winter wheat (Triticum aestivum) to have high NUE, high yield, and be environmentally sustainable. Nine winter wheat experiments were conducted across seven locations from 2011 through 2013. The objectives of this study were to evaluate the impacts of fall-winter, Feekes 4, Feekes 7, and Feekes 9 N applications on winter wheat grain yield, grain protein, and total grain N uptake. Nitrogen treatments were applied as single or split applications in the fall-winter, and top-dressed in the spring at Feekes 4, Feekes 7, and Feekes 9 with applied N rates ranging from 0 to 134 kg ha[superscript]-1. Results indicate that Feekes 7 and 9 N applications provide more optimal combinations of grain yield, grain protein levels, and fertilizer N recovered in the grain when compared to comparable rates of N applied in the fall-winter or at Feekes 4. Winter wheat N management studies from 2006 through 2013 were utilized to develop sensor-based N recommendation algorithms for winter wheat in Kansas. Algorithm RosieKat v.2.6 was designed for multiple N application strategies and utilized N reference strips for establishing N response potential. Algorithm NRS v1.5 addressed single top-dress N applications and does not require a N reference strip. In 2013, field validations of both algorithms were conducted at eight locations across Kansas. Results show algorithm RK v2.6 consistently provided highly efficient N recommendations for improving NUE, while achieving high grain yield and grain protein. Without the use of the N reference strip, NRS v1.5 performed statistically equal to the KSU soil test N recommendation in regards to grain yield but with lower applied N rates. Six corn N fertigation experiments were conducted at KSU irrigated experiment fields from 2012 through 2014 to evaluate the previously developed KSU sensor-based N recommendation algorithm in corn N fertigation systems. Results indicate that the current KSU corn algorithm was effective at achieving high yields, but has the tendency to overestimate N requirements. To optimize sensor-based N recommendations for N fertigation systems, algorithms must be specifically designed for these systems to take advantage of their full capabilities, thus allowing implementation of high NUE N management systems.
25
Nirmaier, Thomas. "A CMOS-based Hartmann-Shack sensor for real-time adaptive optical applications." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968388280.
Full text
26
Johnson, Eric K. "Low Loss Hybrid Waveguide Electric Field Sensor Based on Optical D-fiber." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2153.pdf.
Full text
27
Cheevers, Kevin. "Optical Fibre-Based Hydrophone and Critical Ignition in Detonation Cells." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42793.
Full textAbstract:
This thesis is composed of two distinct parts. The first part of this work addresses the problem of critical ignition behind a decaying shock wave in the context of cellular detonations. Low-pressure (4.1 kPa) shock tube experiments were performed in a thin rectangular channel using the highly-unstable mixture of CH4 + 2O2 and the weakly-unstable mixture of 2H2 + O2 + 7Ar, with Schlieren visualization of the flow field. The dynamics of the lead shock in a detonation cell was reconstructed from measurements of the lead shock position and curvature. The post-shock state and the expansion rate along the path of a Lagrangian particle crossing the lead shock at any given point in the cell cycle were evaluated with the shock jump and shock change equations. The chemical evolution behind the shock was then integrated using a detailed chemistry model. Quenching of the post-shock reaction zone was found within the first half of the detonation cell for both mixtures, with quenching occurring earlier in the highly unstable mixture. Simplified models derived from 1-step and 2-step chemistry models very accurately predict the quenching of the post-shock reactions and the evolution of the ignition delay through the cell.
The second part describes the assembly and characterization of a fibre-optic probe hydrophone (FOPH) for the measurement of shock waves associated with blast-induced neuro-trauma. Compared to traditional polyvinylidene difluoride (PVDF) hydrophones, the assembled FOPH has a higher bandwidth and smaller active diameter, which are comparable to the characteristic time and thickness of shock waves associated with blast-induced neuro-trauma. However, the sensitivity of FOPHs are substantially lower than traditional hydrophones. We assemble a FOPH and provide detailed calculations and measurements of its sensitivity (0.66 mV/MPa) , noise floor, and spatial resolution. The 150 MHz bandwidth, limited by the photodetector, is sufficient for resolving shock waves with over-pressures of up to 174 kPa with 3 measurement points. Experimental measurements of the system noise gives a floor of 260 Pa/√Hz . A detailed noise analysis finds that the system is limited by photodetector noise (215 Pa/√Hz), which is 4x the fundamental shot noise limit, closely followed by a laser noise of 150 Pa/√Hz. We conclude that the system noise floor is insufficient for resolved measurements of the post-shock pressure in the range associated with blast-induced neuro-trauma. From our noise analysis, we quantify the sensitivity enhancement required for resolving this regime, and we conclude that sensitivity-enhancing fibre-coatings could provide a sufficient increase in sensitivity.
28
Bender, William John Havercamp. "A chemical sensor based on surface plasmon resonance on surface modified optical fibers." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40097.
Full textAbstract:
A sensor is described which utilizes the phenomenon of surface plasmon resonance to detect changes in refractive index of chemical or biochemical samples applied to a surface modified optical fiber.
The sensor is constructed by polishing a short section of the lateral surface of an optical fiber to its evanescent field surrounding the fiber core. One or more thin films are applied to the polished section of the fiber to produce the sensing element. One of the films is the metal silver, which acts as the support for the surface plasmon.
Under the proper conditions, TM polarized energy propagating in the fiber can be coupled to a surface plasmon electromagnetic mode on the metal film. This coupling depends on the wavelength, the nature of the fiber, the refractive index and thickness of the thin films applied to the fiber, and the refractive index of a chemical sample in contact with the modified surface. The fiber to plasmon coupling is seen as a large attenuation of the light reaching the distal terminus of the fiber.Ph. D.
29
Zheng, Gang. "Development of advanced birefringent fibre force sensor systems based on frequency modulation continuous wave (FMCW) technology." Thesis, Glasgow Caledonian University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337411.
Full text
30
Yung, Yat Fong. "Digital pixel sensor (DPS) array based on pulse width modulation (PWM) scheme /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20YUNG.
Full text
31
DonlagicÌ, Denis. "Microbend sensor structure based on selective excitation and filtering of the modes in graded index optical fibres." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248635.
Full text
32
Dunn, Peter L. "Development of a video-based slurry sensor for on-line ash analysis." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-02132009-171601/.
Full text
33
Lobato, Bailón Laura. "Internal dynamics of heme-based sensor proteins studied using advanced time-resolved optical spectroscopy." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/pastel-00866894.
Full textAbstract:
Des protéines à base de l'hème sont impliquées dans une large gamme de fonctions biologiques, y compris la respiration, le transport de l'oxygène et la détoxification des xénobiotiques. Surtout, les protéines senseurs bactériens à base de l'hème exploitent les propriétés de liaison de l'hème pour détecter les gaz environnementaux. Cette thèse focalise sur l'étude de la dynamique interne des hémo-protéines senseurs à gaz 6-coordonnées CooA, de Rhodospirillum rubrum et DNR de Pseudomonas aeruginosa, qui sont impliquées dans l'adaptation du métabolisme de l'organisme à son environnement. CooA et DNR, appartenant à la famille importante de protéines catabolites activatrices des gènes, sont des facteurs de transcription qui se lient à l'ADN lors de l'activation par des molécules diatomiques gazeuses, permettant ainsi à la transcription de gènes spécifiques. Les deux protéines senseur potentiellement subissent un important changement conformationnel délocalisé lors de la liaison du ligand physiologique à l'hème (CO pour CooA et NO pour DNR). Ici des techniques avancées de spectroscopie optique sont utilisées pour étudier le mécanisme et la voie moléculaire de l'activation / désactivation dans cette classe de protéines. Des interactions protéine-ADN ont été étudiées avec des techniques de fluorescence à l'équilibre et ultrarapide femtoseconde, en utilisant des substrats d'ADN marqués. Une liaison de l'ADN, sensible au ligand physiologique, dans la gamme d'affinité nanomolaire a été déduite des expériences d'anisotropie. Du " quenching " de la fluorescence du marqueur fluorescent par transfert d'énergie à l'hème natif a été observée et la vitesse de ce processus, qui reflète la distance hème-substrat, a été déterminé directement des cinétiques mesurées de la fluorescence. Cette observation ouvre la perspective d'une cartographie des changements conformationnels globaux de la protéine à l'aide des techniques FRET résolu en temps. Les processus primaires dans les mécanismes de bascule des hémo-senseurs concernent la liaison et la dissociation du ligand de l'hème. Des expériences d'absorption femtosecondes transitoires ont été réalisées afin d'étudier la dynamique de ligands dans CooA et DNR proche de l'hème. Dans DNR, après photodissociation de NO, une recombinaison géminée particulièrement rapide et efficace a été observée. Cela renforce fortement l'hypothèse que des senseurs à NO agissent comme des pièges à ligands. En outre, les barrières énergétiques liées à la migration de CO ont été déterminées dans les deux protéines senseurs par des études de la dépendance de la température. Toutes les protéines senseurs 6- coordonnées, qui fonctionnent par l'échange d'un résidu interne et de la molécule de gaz en tant que ligand de l'hème, démontrent une recombinaison sans barrières et une évasion thermiquement activée du CO de la poche de l'hème. En revanche, la barrière pour l'évasion du CO apparaît plus faible ou même absente pour les systèmes 5-coordonnées, comme cela a été trouvé pour le senseur à hème mycobactérien DosT. Ces résultats mettent en évidence un mécanisme général, où des mouvements intra-protéiques similaires sont nécessaires pour les deux, l'échange de ligand et l'évasion de ligand. Pour des raisons de comparaison, les barrières énergétiques ont également été étudiées dans des variantes de la protéine de transfert d'électrons cytochrome c. Ici, un mécanisme plus complexe de barrières multiples dans la voie d'échappement du ligand a été déduit. Cette propriété est proposée de provenir de la nature plutôt rigide de cette protéine non-senseur, qui contient un hème 6-coordonnée et est dépourvu de voies d'entrée de ligand à l'état natif. Enfin, les processus primaires dans les domaines de l'hème, de type sauvage et de mutants, du senseur à oxygène YddV, récemment découvert dans Escherichia coli, ont été étudiés. En particulier, un rôle important dans la dynamique de ligands a été élucidé pour le résidu tyrosine distale. Ce résidu, qui forme des liaisons hydrogène avec O2 et NO liés à l'hème, a un effet remarquablement discriminant: après dissociation respective de l'hème, il assiste fortement à la reliaison de l'O2, mais favorise l'évasion du NO de la poche de l'hèmeHeme-proteins are involved in a large range of biological functions, including respiration, oxygen transport and xenobiotic detoxification. Importantly, bacterial heme-based sensor proteins exploit the ligation properties of heme to sense environmental gases. This thesis focuses on internal dynamics studies of the 6-coordinate heme-based gas sensor proteins CooA, from Rhodospirillum rubrum and DNR from Pseudomonas aeruginosa that are involved in adaptation of the metabolism of the organism to their environment. CooA and DNR, belonging to the important family of catabolite gene activator proteins, are transcription factors that bind DNA upon gas activation, thus enabling transcription of specific genes. Both sensor proteins are thought to undergo a large and delocalized conformational change upon binding of the physiological ligand to the heme (CO for CooA and NO for DNR). Here advanced optical spectroscopy techniques are used to investigate the mechanism and molecular pathway of activation/desactivation in this class of proteins. DNA-protein interactions were studied with steady-state and femtosecond ultrafast time resolved fluorescence techniques, using labeled DNA substrates. Physiological ligand-sensitive DNA binding in the nanomolar affinity range was deduced from anisotropy experiments. Quenching of the fluorescence label by energy transfer to the native heme in the protein moiety of the complex was observed, and the rate of this process, reflecting the heme-substrate distance, was determined directly from the measured fluorescence decays. This observation opens the perspective of mapping out the global protein conformational changes using time-resolved FRET techniques. The primary processes in heme-based sensor switching mechanisms concern ligand binding and ligand dissociation from the heme. Femtosecond transient absorption experiments were performed in order to study the ligand dynamics in CooA and DNR in the vicinity of the heme. In DNR, upon photodissociation of NO, particularly fast and efficient geminate recombination was observed. This strongly strengthens the hypothesis that NO-sensors act as ligand traps. Also, the energetic barriers involved in CO migration have been determined in both sensor proteins by temperature dependence studies. All 6-coordinate heme-based sensor proteins that function via the exchange of an internal residue and the gas molecule as a heme ligand, display barrierless recombination and a thermally activated CO-escape out of the heme pocket. By contrast, the barrier for the CO-escape appears smaller or absent for 5-coordinate systems, as has been found for the mycobacterial heme-sensor DosT. These findings point to a general mechanism, where similar protein motions are required for both, ligand exchange and ligand escape. For reasons of comparison, the energetic barriers have also been studied in ligand binding variants of the electron transfer protein cytochrome c. Here, a more complex mechanism of multiple barriers in the ligand escape pathway was deduced. This feature is proposed to reflect the rather rigid nature of this non-sensor protein, which contains a 6-coordinate heme and is devoid of ligand entry pathways in the native state. Finally, the primary processes occurring in the wild type and mutant heme domains of the recently discovered oxygen sensor YddV from Escherichia coli were investigated. In particular, an important role in the ligand dynamics was elucidated for the distal tyrosine residue. This residue hydrogen bonds to heme-bound O2 and NO molecules and was found to have a remarkably discriminating effect: after respective dissociation from the heme, it strongly promotes O2 rebinding, but favors NO escape from the heme pocket
34
Oh, Ki Dong. "Optical Fiber Fabry-Perot Interferometer based Sensor Instrumentation System for Low Magnetic Field Measurement." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29687.
Full textAbstract:
This dissertation proposes a miniaturized optical fiber based sensor system for the measurement of 3-dimensional vector magnetic fields. The operation of the sensor system is based on the detection of magnetostrictive dimensional changes in the sensor gage using a modified extrinsic Fabry-Perot Interferometer configuration. Because of the magnetostrictive reflector the gap length depends on the magnetic fields applied to the sensor. Since the diameter of the magnetostrictive sensor gage is 125 micrometer which is the same as that of the input/output fiber, the sensor is simply constructed by inserting the sensor gage and the input/output fiber into a small glass tube. The glass tube serves as both an aligner for the sensor gage and input/out fiber, and a passive temperature compensator. In addition, it also enhances the mechanical strength and compactness of the sensor. This sensor design shows 98 percent suppression of the thermally induced sensor output changes. The linear output of the sensor system is enhanced by transverse field annealing which increases magnetostrictive induction in the ferromagnetic sensor gage material and controls the sensor gage geometry. A 5-times increase in sensor sensitivity is obtained with the transverse field annealing and the use of a new magnetostrictive material. A modified sensor gage endface demonstrates 92 percent of fringe visibility, which further improves the performance of the interferometer. The signal fading in the interferometric sensors at the peak or bottom of a fringe is reduced by using a quadrature signal demodulation method. The system has been shown to have a resolution better than 100 nT over a measurement range from 100 to 40,000 nT. This research is supported financially by the Phillips Laboratory of the U.S. Air Force.Ph. D.
35
Paap, Arie Jacobus. "Development of an optical sensor for real-time weed detection using laser based spectroscopy." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/1282.
Full textAbstract:
The management of weeds in agriculture is a time consuming and expensive activity, including in Australia where the predominant strategy is blanket spraying of herbicides. This approach wastes herbicide by applying it in areas where there are no weeds. Discrimination of different plant species can be performed based on the spectral reflectance of the leaves. This thesis describes the development of a sensor for automatic spot spraying of weeds within crop rows. The sensor records the relative intensity of reflected light in three narrow wavebands using lasers as an illumination source.
A prototype weed sensor which had been previously developed was evaluated and redesigned to improve its plant discrimination performance. A line scan image sensor replacement was chosen which reduced the noise in the recorded spectral reflectance properties. The switching speed of the laser sources was increased by replacing the laser drivers. The optical properties of the light source were improved to provide a more uniform illumination across the viewing area of the sensor. A new opto-mechanical system was designed and constructed with the required robustness to operate the weed sensor in outdoor conditions. Independent operation of the sensor was made possible by the development of hardware and software for an embedded controller which operated the opto-electronic components and performed plant discrimination.
The first revised prototype was capable of detecting plants at a speed of 10 km/h in outdoor conditions with the sensor attached to a quad bike. However, it was not capable of discriminating different plants. The final prototype included a line scan sensor with increased dynamic range and pixel resolution as well as improved stability of the output laser power. These changes improved the measurement of spectral reflectance properties of plants and provided reliable discrimination of three different broadleaved plants using only three narrow wavelength bands. A field trial with the final prototype demonstrated successful discrimination of these three different plants at 5 km/h when a shroud was used to block ambient light.
A survey of spectral reflectance of four crops (sugarcane, cotton, wheat and sorghum) and the weeds growing amongst these crops was conducted to determine the potential for use of the prototype weed sensor to control spot-spraying of herbicides. Visible reflectance spectra were recorded from individual leaves using a fibre spectrometer throughout the growing season for each crop. A discriminant analysis was conducted based on six narrow wavebands extracted from leaf level spectral reflectance measured with a spectrometer. The analysis showed the potential to discriminate cotton and sugarcane from
36
Qian, Zexin. "The Impact of Humidity on an Optical Chemical Sensing Device for Non-invasive Exhaled Gas Monitoring." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347710.
Full text
37
Raman, Baranidharan. "Sensor-based machine olfaction with neuromorphic models of the olfactory system." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4984.
Full textAbstract:
Electronic noses combine an array of cross-selective gas sensors with a pattern recognition engine to identify odors. Pattern recognition of multivariate gas sensor response is usually performed using existing statistical and chemometric techniques. An alternative solution involves developing novel algorithms inspired by information processing in the biological olfactory system. The objective of this dissertation is to develop a neuromorphic architecture for pattern recognition for a chemosensor array inspired by key signal processing mechanisms in the olfactory system. Our approach can be summarized as follows. First, a high-dimensional odor signal is generated from a chemical sensor array. Three approaches have been proposed to generate this combinatorial and high dimensional odor signal: temperature-modulation of a metal-oxide chemoresistor, a large population of optical microbead sensors, and infrared spectroscopy. The resulting high-dimensional odor signals are subject to dimensionality reduction using a self-organizing model of chemotopic convergence. This convergence transforms the initial combinatorial high-dimensional code into an organized spatial pattern (i.e., an odor image), which decouples odor identity from intensity. Two lateral inhibitory circuits subsequently process the highly overlapping odor images obtained after convergence. The first shunting lateral inhibition circuits perform gain control enabling identification of the odorant across a wide range of concentration. This shunting lateral inhibition is followed by an additive lateral inhibition circuit with center-surround connections. These circuits improve contrast between odor images leading to more sparse and orthogonal patterns than the one available at the input. The sharpened odor image is stored in a neurodynamic model of a cortex. Finally, anti-Hebbian/ Hebbian inhibitory feedback from the cortical circuits to the contrast enhancement circuits performs mixture segmentation and weaker odor/background suppression, respectively. We validate the models using experimental datasets and show our results are consistent with recent neurobiological findings.
38
Holmberg, Patrik. "Laser processing of Silica based glass." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.
Full textAbstract:
The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.
QC 20150924
39
Chen, Ou. "Development of offset locking based distributed sensor, and, Study of polarization effects in optical fibers." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26869.
Full textAbstract:
This thesis is composed of two main sections.
The first section is the development of an optical fiber sensor. This new sensor system has been simulated by a Matlab program that considers the distributed feedback lasers' broader linewidth compared with that of frequency stabilized Nd:YAG lasers.
The second section involves research on polarization effects in the optical fiber. In this thesis it is proven that only three states of polarization are required to determine the principle state of polarization vector. In addition, polarization effects in fiber Bragg gratings are investigated in this work. To measure the polarization dependent loss of the fiber Bragg grating for the reflection wavelength, an optical circulator is used. A problem arises since the circulator's polarization dependent loss contributes to the measurement result; this effect is often ignored. In this thesis, a test set has been developed to eliminate this uncertainty effect through a three-step procedure using the Jones Matrix method.
40
Zhang, Feng Hong. "A novel optical fibre sensor based on inter-fibre distributed coupling for particle concentration measurement." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361510.
Full text
41
Tu, Minh Hieu. "Investigation of metal nanomaterials as a sensing element in LSPR-based optical fibre sensor development." Thesis, City University London, 2014. http://openaccess.city.ac.uk/5919/.
Full textAbstract:
This thesis aims to explore and demonstrate the potential of using optical fibres both as a waveguide material and a transducer for wide sensing applications, based on a comprehensive review of the localised surface plasmon resonance (LSPR) phenomenon, which occurs at a nanoscale level when light interacts with metallic nanoparticles at a resonance wavelength. The LSPR effect of metallic nanomaterials has shown a strong dependence on the local surrounding environment. A small change for example in the refractive index or in the solution concentration can result in a variation in the LSPR spectrum. Based on this underpinning sensing mechanism, a portable system using an optical fibre coated with gold nanoparticles (AuNPs) as a sensing probe has been developed and tested for the refractive index measurement. Coupled with this, a systematic approach has been developed and applied in this work to optimize the performance of the developed system by considering several key factors, such as the size of nanoparticles produced, pH, coating time and coating temperature. The above optimised probes coated with gold-nanoparticles are further cross-compared with those optimized but coated with gold nanorods with a high aspect ratio. Both types of probes are also prepared for a specific biosensing application based on the antibody-antigen interaction to create wavelength-based sensors for the detection of anti-human IgG. Both probes have exhibited excellent refractive index (RI) sensitivity, showing ~914 nm/RIU (refractive index unit) for the probe coated with gold nanoparticles and ~601 nm/RIU for the one coated with gold nanorods. When using the modified probes for the detection of anti-human IgG, both probes are able to achieve a good LOD (limit of detection) at 1.6 nM. Based on the above cross-comparison, further research has been undertaken to explore the potential of nanoparticles of the alloy of gold and silver, with an aim to combine the robustness of gold and the excellent LSPR effect of silver. To do so, various alloy particles with varied gold/silver ratio and sizes have been prepared and tested for their respective refractive index sensitivities. The probe coated with alloy particles with bigger size and higher silver content has shown better performance in RI sensing. The work has shown a clear relationship between the size of alloys, the content ratio of alloys and RI sensitivity. Research has also been undertaken in this thesis to explore the excellent LSPR effect of hollow nanoparticles resulting from the enhanced coupling between the interior and exterior of the hollow particles. Gold hollow nanocages have been successfully synthesised and tested with different hollowness and a LSPR sensor coated with gold nanocages has shown an excellent sensitivity as high as ~1933 nm/RIU, which is more than 3 times higher than that coated with AuNPs. This result has confirmed that a significant improvement in sensitivity can be made possible for further biosensing as well as chemical sensing applications.
42
Kim, Chan Kyu. "Development of bio-photonic sensor based on laser-induced fluorescence." Diss., Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11052007-092200.
Full text
43
SARAN, ANISH. "MEMS BASED FABRY PEROT PRESSURE SENSOR AND NON-ADHESIVE INTEGRATION ON OPTICAL FIBER BY ANODIC BONDING." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1084719088.
Full text
44
Bechhoefer, Eric R. "An indicator of message quality for a single optical sensor using a template based tracking algorithm." Thesis, Monterey, Calif. : Naval Postgraduate School, 1992. http://handle.dtic.mil/100.2/ADA252704.
Full text
45
Sargeant, Ramon Bradley. "A multi-axial optical fibre and linear polarizer based force and torque sensor for dexterous robotic fingertips." Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/a-multiaxial-optical-fibre-and-linear-polarizer-based-force-and-torque-sensor-for-dexterous-robotic-fingertips(a9c419a3-901e-4a56-9b02-00648539d17e).html.
Full textAbstract:
As robots play a more pervasive role in our everyday activities more and more research emphasis is being placed on having robots interact directly with humans, whether in terms of taking care of the elderly, medical interventions or performing dangerous or hazardous tasks. Another trend is for robots to use existing human tools to perform desired actions since it is also not always possible or cost effective to design special tools for every robot. This trend has led to the development of anthropomorphic dexterous manipulators that can perform equally or better than the human hand. Thus the accelerating trend is not only to design a dexterous manipulator but to focus on its ability to grasp and manipulate different and sometimes unknown objects. One of the most researched types of grasp is the precision grasp which accounts for over 80 % of the grasps performed by humans on a daily basis. Precision grasps are grasps involving the fingertips and are generally used for tasks that require fine manipulation skills. Fingertip sensors are therefore important for dexterous manipulators since humans can identify salient properties of an object and formulate effective manipulation strategies solely by grasping the object. This PhD project focuses on developing fingertip sensors, specifically force and torque fingertip sensors that can be integrated into the fingertip of an existing dexterous manipulator and gather contact force and torque information during a grasping event. Another goal is to make the sensor magnetic resonant (MR) compatible so that it can be used in high magnetic environments, as in the case of medical, magnetic resonance imagining applications. To accomplish these goals two sensors were developed based on light intensity modulation and novel sensing structures. Optical sensing schemes were chosen because they are not susceptible to magnetic interference, the sensor and its light source can be separated by long distances without significant signal attenuation and the size and weight of the actual sensing element can be reduced since the processing electronics can be positioned far from the sensing structure. The first sensor developed, as part of this PhD work, was a 2-DOF sensor which used a combination of axially-aligned fibres and linear polarizers to modulate the light to measure the applied force and torque respectively. The use of linear polarizers as the main sensing technique for force and torque sensing is a new area of research since linear polarizers have a defined response curve and can be easily cut into any desired shape and size. The experiments conducted with the 2-DOF sensor showed that the linear polarizer response was superior to traditional axially-aligned and reflective techniques and it was tolerant of small deviations and twists in the sensing structure. The second sensor improved on the first sensor by increasing the number of degrees of freedom from two to six by using a parallel-type 3-UPS (Universal Prismatic Spherical) sensing structure to allow measuring six degrees of movement. All of the joints of the sensing structure were made of nitinol flexures to reduce friction and all of the links were made of plastic and bonded together to produce a flexible but light and strong structure. Another improvement was that all of the optical modulation sensors on the sensing structure were based on linear polarizers thereby reducing the possibility of misalignment errors caused by the transmitting and receiving fibres moving out of axial alignment. The new sensor therefore satisfies the design requirements and the experiments conducted showed that Light Intensity Modulation (LIM) using linear polarizers and an appropriate sensing structure can produce an accurate and versatile force and torque sensor.
46
Symington, Andrew Colquhoun. "Cooperative, range-based localization for mobile sensors." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:dd4b793b-3cf7-45d0-8972-76fdd870e57c.
Full textAbstract:
This thesis describes the development of an offline, cooperative, range-based localization algorithm for use in settings where there is limited or no access to a positioning infrastructure. Motivating applications include underground animal tracking and indoor pedestrian localization. It is assumed that each sensor performs dead reckoning to estimate its current position, relative to a starting point. Each measurement adds error, causing the position estimate to drift further from the truth with time. The key idea behind the proposed algorithm is to use opportunistic radio contacts to mitigate this drift, and hence localize with greater accuracy. The proposed algorithm first fuses radio and motion measurements into a compact graph. This graph encodes key positions along sensor trajectories as vertices, and distance measurements as edges. In so doing, localization is cast as the graph realization problem: assigning coordinates to vertices, in such a way that satisfies the observed distance measurements. The graph is first analysed to certify whether it defines a localization problem with a unique solution. Then, several algorithms are used to estimate the vertex coordinates. These vertex coordinates are then used to apply piecewise corrections to each sensor's dead reckoning trajectory to mitigate drift. Finally, if sufficient anchors are available, the corrected trajectories are then projected into a global coordinate frame. The proposed algorithm is evaluated in simulation for the problem of indoor pedestrian tracking, using realistic error models. The results show firstly that 2D and 3D problems become provably more localizable as more anchors are used, and as the experiment duration increases. Secondly, it is shown that widely-used graph realization algorithms cannot be used for localization, as the complexity of these algorithms scales polynomially or greater with graph vertex count. Thirdly, it is shown a novel piecewise drift correction algorithm typically works well compared to a competing approach from the literature, but rare and identifiable graph configurations may cause the method to underperform.
47
Pradhan, Manik. "Development of a diode-laser based optical sensor for continuous monitoring of trace gases in the atmosphere." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492655.
Full textAbstract:
The use of continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near-infrared (IR) region has great potential for the design of ultra-sensitive, compact, robust and cost-effective novel optical sensors capable of detecting trace species present in the atmosphere. The research work presented in this thesis focuses on the development and implementation of a fully automated, cryogen-free and compact cw-CRD spectrometer, combined with adsorbent filled dual-trap sample pre-concentration for monitoring trace C2H2 mixing ratios in ambient air.
48
Liu, Huanhuan. "A novel optical bio-chemical sensor based on hybrid nanostructures of Bowtie nanoantennas and Fabry-Perot Interferometer." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-01064196.
Full textAbstract:
Nowadays, the increasing concern for environmental analysis and food quality control, as well as medical needs such as fast diagnosis in case of emergency events, leads to a growing need for new generations of chemical and biological sensors. These devices should have high sensitivity and reliability, perform specific detection of molecules and enable multiple parallel sensing, while being cheap, portable, fast and easy to use. Thus, a general trend tends towards bio-chemical sensors which are on-chip integrated, label-free, and compatible with standard micro-technologies. Photonic dielectric devices based on porous silicon and metallic nanostructures based on plasmon resonances are good candidates to fulfill the above requirements. Porous silicon is a biocompatible material, with a huge specific surface providing a sensitivity enhancement by several orders of magnitude compared to bulk materials; furthermore, its refractive index and thickness can be easily tuned, enabling for the realization of a large variety of photonic designs. Metallic nanostructures provide high confinement and strong field enhancement in sub-wavelength regions, leading to high sensitivities; combined with fluorescence or other sensing mechanisms such as Raman or IR spectroscopy, they have already demonstrated increased sensing potential. The realization of a hybrid device combining both elements would be highly interesting, since it could yield the advantages of both elements, and the photonic structure could shape the plasmonic resonance to develop ultrasensitive devices with narrow resonance linewidth and increased sensing depth. In this context, we realized and studied a novel hybrid photonic / plasmonic device exploiting the coupling between the surface plasmon resonance of a bowtie nano - antenna (NAs) array and the photonic modes of porous silicon (PSi) interferometer. We designed and fabricated a NAs array with resonance wavelength ~ 1.3μm on a homogeneous PSi interferometer. A thin spacing silica layer with controllable density protects the pores of PSi layer and provides a smooth surface for the fabrication of NAs. The coupling mechanisms of two elements - NA array and interferometer, are studied with 2 models, which are interferometer approach and resonator approach. The interferometer approach is focused on studying the influence of NAs array as a homogeneous layer on the fringes shift of the interferometer. For resonator approach, the coupled mode theory is applied. With these models, strong coupling between both elements are discovered: splitting. In the case of viii smaller environment variation, the hybrid device gains 5-10 fold sensitivity enhancement vs. 2 elements alone. The controllable SiO2 layer allows us to sense the index variation within PSi interferometer. This opens a route towards double parallel sensing. The development of the theoretical models under different environment is ongoing, which is expected to utilize the strong coupling for the sensing. A further investigation of the sensing potential of the hybrid device would be expected. And the 2 elements constituting the hybrid structure - the interferometer and the NA array - could be modified in order to enlarge the study to a wider family of devices with greater properties and performances. This work was performed within the framework of the program "Groups of Five Ecoles Centrales" between China Scholarship Council (CSC) and Lyon Institute of Nanotechnologies (INL, CNRS UMR 5270). The project has been supported by the Nanolyon technology platform at INL.
49
Brush, Ursula Jane. "Design and Validation of an Intensity-Based POF Bend Sensor Applications in Measuring Three-Dimensional Trunk Motion." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1269456459.
Full text
50
Shillig, Tyler. "Multi-point temperature sensing in gas turbines using fiber-based intrinsic Fabry-Perot interferometers." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33612.
Full textAbstract:
Due to their compact size, sensitivity, and ability to be multiplexed, intrinsic Fabry-Perot interferometers (IFPIs) are excellent candidates for almost any multi-point temperature or strain application, and it is well-known that using a single-mode lead-in fiber, a multi-mode fiber section as the Fabry-Perot cavity, and an additional single-mode fiber as the tail results in a structure that generates strong interference fringes while remaining robust. Though the basic principles behind these sensors are understood, to the best of the authorâ s knowledge there hasnâ t been a thorough investigation into the design and fabrication of a chain of multiplexed IFPI sensors for industrial use in an environment where serious issues associated with the size of the test coupon, sensor placement, and mechanical reinforcement of the fiber could arise. This thesis details the preparation and results of this investigation. It turns out that fabricating a sensor chain with appropriate sensor spacing and excellent temperature response characteristics proved a significant challenge, and issues addressed include inter-sensor interference, high-temperature mechanical reinforcement for bare fiber sections, and high bending losses. After overcoming these problems, a final sensor chain was fabricated and characterized. This chain was then subjected to a battery of tests at the National Energy Technology Laboratory (NETL), where four multiplexed sensors were installed on a 2â x2â coupon in a simulated gas turbine environment. Final results are presented and analyzed. The work that went into developing this chain lays the foundation for future efforts in developing quasi-distributed temperature sensors by identifying potential obstacles and fundamental limitations for certain approaches.Master of Science