Linijinių skalių kalibravimo įrenginiuose vienu iš pagrindinių linijos padėties kalibravimo paklaidos sandų yra geometrinės komparatoriaus paklaidos. t.y. paklaidos, susijusios su karietėlės judesio nuokrypiais – jos mažais kampiniais svyravimais apie pagrindinio judesio ašį ir jai statmenas ašis bei linijiniai poslinkiai išilgai šių statmenų ašių. Dėl Abbe principo nesilaikymo, reikšmingiausiais yra karietėlės kampiniai svyravimai apie minėtąsias statmenas ašis. / One of the main components of a line position calibration error in linear scale calibrators are geometrical errors of the comparator, i.e. the errors associated with the carriage’s movement deviations – its slight angular fluctuations about the main movement axis and the axes perpendicular thereto, and the linear displacements along those perpendicular axes. The most important are the carriage’s angular fluctuations about the abovementioned perpendicular axes due to nonobservance of Abbe principle.

The objective of this thesis was to develop applications of monolithic fiber devices and actively controlled fibers. A special twin-core fiber known as a ‘Gemini’ fiber was used to construct equal arm-length fiber interferometers, impervious to temperature and mechanical perturbations. A broadband add/drop multiplexer was constructed by inscribing fiber Bragg gratings in the arms of a Gemini Mach-Zehnder interferometer. A broadband interferometric nanosecond switch was constructed from a micro-structured Gemini fiber with incorporated metal electrodes. Additionally, a Michelson fiber interferometer was built from an asymmetric twin-core fiber and used as a high-temperature sensor. While the device could be readily used to measure temperatures below 300 °C, an annealing process was required to extend the range up to 700 °C. The work included development, construction and evaluation of the components along with numerical simulations to estimate their behaviors and to understand the underlying processes. The thesis also explored the use of electrically controlled fibers for filtering in the microwave domain. An ultra-narrow phase-shifted fiber Bragg grating inscribed in a fiber with internal electrodes was used as a scanning filter to measure modulation frequencies applied to an optical carrier. A similar grating was used inside a dual-wavelength fiber laser cavity, to generated tunable microwave beat frequencies. The studied monolithic fiber interferometers and actively controlled fibers provide excellent building blocks in such varied field as in microwave photonics, telecommunications, sensors, and high-speed switching, and will allow for further applications in the future. / Syftet med denna avhandling var att utveckla tillämpningar av monolitiska fiber komponenter samt aktivt kontrollerbara fiber. En speciell tvillingkärnefiber, även kallad ’Geminifiber’ användes för att konstruera fiber interferometrar med identisk armlängd som ej påverkas av termiska och mekaniska variationer. En bredbanding utbytarmultiplexor konstruerades genom att skriva in fiber Bragg gitter inuti grenarna på en Gemini Mach-Zehnder interferometer. Geminifibrer med interna metallelektroder användes för att konstruera en bredbandig nanosekundsnabb interferometrisk fiberomkopplare. Därtill användes en tvillingkärnefiber som en hög-temperatursensor. Även om komponenten direkt kan användas upp till 300 °C, måste den värmebehandlas för att kunna användas upp till 700 °C. Arbetet har innefattat utveckling, konstruktion och utvärdering av komponenterna parallellt med numeriska simuleringar för att analysera deras beteenden samt få insikt om de underliggande fysikaliska processerna. Avhandlingen behandlar även tillämpningar av en elektriskt styrbar fiber för att filtrera radiofrekvenser. Ett ultrasmalt fasskiftat fiber Bragg gitter skrevs in i en fiber med interna elektroder och användes som ett svepande filter för att mäta modulationsfrekvensen på en optisk bärfrekvens. Ett liknande gitter användes inuti en laserkavitet för att generera två olika våglängder samtidigt. Dessa två våglängder användes sedan för att generera en svävningsfrekvens i mikrovågsbandet. De undersökta monolitiska fiberinterferometrarna och de aktivt styrbara fibrerna erbjuder en utmärkt byggsten inom så pass skiljda områden som Mikrovågsfotonik, Telekommunikation, Sensorer samt Höghastighets-omkopplare och bör kunna användas inom många olika tillämpningar i framtiden. / <p>QC 20130226</p>

No description available.

Reconstruction of continuous signals from a number of their discrete samples is central to digital signal processing. Digital devices can only process discrete data and thus processing the continuous signals requires discretization. After discretization, possibility of unique reconstruction of the source signals from their samples is crucial. The classical sampling theory provides bounds on the sampling rate for unique source reconstruction, known as the Nyquist sampling rate. Recently a new sampling scheme, Compressive Sensing (CS), has been formulated for sparse signals. CS is an active area of research in signal processing. It has revolutionized the classical sampling theorems and has provided a new scheme to sample and reconstruct sparse signals uniquely, below Nyquist sampling rates. A signal is called (approximately) sparse when a relatively large number of its elements are (approximately) equal to zero. For the class of sparse signals, sparsity can be viewed as prior information about the source signal. CS has found numerous applications and has improved some image acquisition devices. Interesting instances of CS can happen, when apart from sparsity, side information is available about the source signals. The side information can be about the source structure, distribution, etc. Such cases can be viewed as extensions of the classical CS. In such cases we are interested in incorporating the side information to either improve the quality of the source reconstruction or decrease the number of the required samples for accurate reconstruction. A general CS problem can be transformed to an equivalent optimization problem. In this thesis, a special case of CS with side information about the feasible region of the equivalent optimization problem is studied. It is shown that in such cases uniqueness and stability of the equivalent optimization problem still holds. Then, an efficient reconstruction method is proposed. To demonstrate the practical value of the proposed scheme, the algorithm is applied on two real world applications: image deblurring in optical imaging and surface reconstruction in the gradient field. Experimental results are provided to further investigate and confirm the effectiveness and usefulness of the proposed scheme.

Large area high throughput metrology plays an important role in several technologies like MEMS. In current metrology systems the parallel operation of multiple metrology probes in a tool has been hindered by their bulky sizes. This study approaches this problem by developing a metrology technique based on miniaturized scanning grating interferometers (μSGIs). Miniaturization of the interferometer is realized by novel micromachined tunable gratings fabricated using SOI substrates. These stress free flat gratings show sufficient motion (~500nm), bandwidth (~50 kHz) and low damping ratio (~0.05). Optical setups have been developed for testing the performance of μSGIs and preliminary results show 6.6 μm lateral resolution and sub-angstrom vertical resolution. To achieve high resolution and to reduce the effect of ambient vibrations, the study has developed a novel control algorithm, implemented on FPGA. It has shown significant reduction of vibration noise in 6.5 kHz bandwidth achieving 6x10-5 nmrms/√Hz noise resolution. Modifications of this control scheme enable long range displacement measurements, parallel operation and scanning samples for their dynamic profile. To analyze and simulate similar optical metrology system with active micro-components, separate tools are developed for mechanical, control and optical sub-systems. The results of these programs enable better design optimization for different applications.

The aim of this project was to develop a passive optical compensating arrangement that would allow the formation and continued stability of interference patterns over a long timescale and also to investigate optical wave scattering in thick gratings at extreme angles of scattering. A novel passive arrangement based on a Sagnac interferometer is described that produces interference patterns more stable than those produced by a conventional arrangement. An analysis of the arrangement is presented that shows it to be an order of magnitude more stable than an equivalent conventional approach. The excellent fringe stability allowed holographic gratings with small periods (~ 0.5 μm) to be written in photorefractive lithium niobate with low intensity writing fields (~mW/cm2) produced by a He:Ne laser, despite long grating fabrication times (~ 1000 s). This was possible because the optical arrangement compensated for phase shifts introduced by translational and rotational mirror motion caused by environmental perturbations. It was shown that the rapid introduction of a phase shift in one of the writing fields can change the direction of energy flow in the two-wave mixing process. It was found that the improvement in stability of the modified Sagnac arrangement over a conventional interferometer decreased when the crossing angle was increased and that the point about which the mirrors are rotated greatly affects the stability of the arrangement. For a crossing angle of 12 degrees, the modified Sagnac arrangement is more than twice as stable when the mirrors are rotated about their midpoints, rather than their endpoints. Investigations into scattering in the extremely asymmetrical scattering (EAS) geometry were undertaken by scattering light from a 532nm Nd:YAG laser off gratings written in photorefractive barium titanate and lithium niobate. Despite the difficulties posed by background noise, there was very good agreement between the observed scattered field and that predicted by a previously established theoretical model. Thus, this work represents the first experimental observation of EAS in the optical part of the spectrum.

Gas composition and analysis forms a large field of research whose requirements demand that measurement equipment be as affordable, uncomplicated and convenient as possible. The precise quantitative composition of an atmospheric, industrial or chemically synthesised sample of gas is of utmost importance when inferring the properties and nature of the environment from which the sample was taken, or for inferring how a prepared sample will react in its application. The most popular and widely used technique to achieve this is Gas Chromatography-Mass Spectrometry (GCMS) and, without a doubt, this technique has set the standard for gas analysis. Despite the accuracy of the GCMS technique, the equipment itself is bulky, expensive and cannot be applied readily to field work. Instead, most field work is conducted using a single gas detector, capable only of detecting one particular molecule or element at a time. Presented here is an interferometric technique that theoretically, has the ability to address all three issues of bulkiness, affordability and convenience, whilst not being limited to one particular element or molecule in its analysis. Identifying the unknown constituents of a gaseous mixture using the proposed method, employs the optical refractive properties of the mixture to determine its composition. A key aspect of this technique is that the refractive index of an arbitrary mixture of gases will vary depending on pressure and wavelength1. The Lorentz-Lorenz formula and the Sellmeier equations form the foundation of the theoretical background. The optical refractive properties of air and other atmospheric gases have been well established in the literature. The experimental investigations described here have been conducted based on this, insofar as no analysis has been conducted on gases that do not naturally occur in reasonable abundance in the atmosphere. However this does not in any way preclude the results and procedure developed from applying to a synthesised gas mixture. As mentioned, the platform of this technique relies on the pressure and wavelength dependence of the refractivity of the gas. The pressure dependence of the system is easily accounted for, in making this claim however it is still imperative the mixture be impervious to contamination from the wider atmosphere. Wavelength dependence however is perhaps slightly more difficult to accommodate. Multiple lasers, of differing wavelength form the radiative sources which underpin the method developed. Laser sources were chosen because of their coherence, making it easy to produce interference, when combined with the inherent stability of the Sagnac interferometer, provides for a very user friendly system that is able to quickly take results. The other key part of the experimental apparatus is the gas handling system, the gas(es) of interest need to be contained within an optical medium in the path of one of the beams of the interferometer. Precise manipulation of the pressure of the gas is critical in determining concentration, this has been achieved through the use of a gas syringe whose plunger is moved on a finely threaded screw, and measured on a digital manometer. The optical setup has also been explored, specifically in ruling out the use of such radiative sources as passing an incandescent source through a monochromator or the use of LED's to produce interference before settling on lasers to produce the required interference. Finally, a comprehensive theoretical background has been presented using classical electromagnetic theory as well as confirmation from a quantum perspective. The theoretical background for this study relies upon the Lorentz-Lorenz formula. It is commonly presented either from a classical or quantum perspective, in this work both classical and quantum mechanical treatments are given whilst also showing how each confirms the other. Furthermore, a thorough investigation into the dispersion functions of each of the major components of the atmosphere has been compiled from the study of refractivity on individual gases from other authors, in some cases, where no work has been done previously, this has been derived. The technique developed could be considered an ample addition to gas analysis techniques in certain circumstances in terms of expense, convenience and accuracy. The system can predict relative quantities of constituents of the atmosphere to at least 3%. The method described here would allow researchers more time to concentrate on actual results and more resources to allocate to broadening intellectual horizons. This would certainly justify further development.

Darmstadt, Techn. Universiẗat, Diss., 2007.

University, Diss., 1998--Konstanz.

Orientador: Elnatan Chagas Ferreira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-15T01:31:53Z (GMT). No. of bitstreams: 1 Melo_FernandoFerreirade_D.pdf: 5797933 bytes, checksum: a063234832f57c466d1189c44c7fffaa (MD5) Previous issue date: 2009 / Resumo: Esta tese apresenta o estudo e o projeto de um processador eletrônico do sinal de um interferômetro de Sagnac a fibra óptica que procura atender especificações para aplicação em navegação inercial. Estudou-se o comportamento de Girômetros a fibra óptica com modulação de fase senoidal através de modelos e simulações de algumas técnicas de processamento do sinal fotodetectado. Procurou-se responder questões como o sinal mínimo detectável para processadores de sinal específicos, como a técnica Lock-in e da técnica Mean Value. A técnica Mean Value foi modificada visando facilitar a implementação eletrônica e melhorar o desempenho em relação à proposta original. Compromissos entre estabilidade e pontos de operação com melhor resolução, na medida da diferença de fase de Sagnac, foram estabelecidos para o processador projetado. Este processador foi aplicado a um giroscópio óptico projetado por pesquisadores do IEAv/CTA, em São José dos Campos/SP. / Abstract: This thesis presents the study and design of an electronic signal processor for an optical-fiber Sagnac interferometer aimed at inertial navigation applications. The fiberoptic gyroscope behavior under sinusoidal phase modulations was studied through models and simulation of some signal processing techniques. It was attempted to answer questions like lowest detectable signal for some particular processors, such as synchronous (lock-in) detection and mean value. Modifications to the mean value technique aimed at improving its performance and easing its electronics implementation are presented. Tradeoffs between stability and resolution in Sagnac phase difference measurement were determined for the processor designed and for specific points of operation. This processor was used to extract rotation information from a fiber-optic gyroscope designed and assembled by IEAV/CTA investigators based at São José dos Campos/SP. / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica