Download or read book Adaptive Self mixing Interferometry for Metrology Applications written by Reza Atashkhooei and published by . This book was released on 2014 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the laser based techniques proposed for metrology applications, classical interferometers offer the highest precision measurements. However, the cost of some of the elements involved and the number of optical components used in the setup complicates using them in several industrial applications. Apart from cost, the complexities due to optical alignment and the required quality of the environmental conditions can be quite restrictive for those systems. Within the category of optical interferometers, optical feedback interferometry (OFI), also called self-mixing interferometry (SMI) has the potential to overcome some of the complexities of classical interferometry. It is compact in size, cost effective, robust, self-aligned, and it doesn't require a large number of optical components in the experimental configuration. In OFI, a portion of the emitted laser beam re-enters to the laser cavity after backreflection from the target, causing the wavelength of the laser to change, modifying the power spectrum and consequently the emitted output power, which can be detected for measurement purposes. Thus, the laser operates simultaneously as the light source, the light detector, and as the ultra-sensitive coherent sensor for optical path changes. The present PhD pursued improving the performance of OFI-based sensors using a novel and compact optical system. A solution using an adaptive optical element in the form of a voltage programmable liquid lens was proposed for automated focus adjustments. The amount of backreflected light re-entering the laser cavity could be controlled, and the laser feedback level was adjusted to the best condition in different situations, enabling the power signal to be adjusted to the best possible conditions for measurement. Feedback control enabled the proposal of a novel solution called differential OFI, which improved the measurement resolution down to the nanometre order, even if the displacements were below half-wavelength of the laser, for first time in OFI sensors. Another relevant part of the PhD was devoted to the analysis of speckle-affected optical power signals in feedback interferometers. Speckle effect appears when the displacements of the target are large, and introduces an undesired modulation of the amplitude of the signal. After an analysis of the speckle-affected signal and the main factors contributing to it, two novel solutions were proposed for the control of speckle noise. The adaptive optical head developed previously was used in a real time setup to control the presence of speckle effect, by tracking the signal to noise ratio of the emitted power, and modifying the spot size on the target when required using a feedback loop. Besides, a sensor diversity solution was proposed to enable enhancements in signal detection in fast targets, when real time control could not be applied. Finally, two industrial applications of the technique with the presence of different levels of speckle noise have been presented. A complete measurement methodology for the control of motor shaft runout in permanent magnet electrical motors, enabling complete monitoring of the displacement of the shaft has been developed and implemented in practice. Results here are validated with those obtained using a commercial laser Doppler vibrometer, an equipment with a much higher cost. A second application in the monitoring the displacement of polymer-reinforced beams used in civil engineering under dynamic loading was also demonstrated. Results here are validated using a conventional contact probe (a Linear Vertical Differential Transducer, LVDT). Both applications show that with controlled speckle features OFI performs adequately in industrial environments as a non-contact proximity probe with resolution limited by the constraints defined by the setup.
Download or read book Self mixing Interferometry for Absolute Distance Measurement written by Mengkoung Veng (docteur en photonique).) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-mixing Interferometry has been studied extensively in the last five decades in various sensing applications. Sensors under the SMI technique have the laser diode as the light source, the interferometer, and the detector. The light from the laser diode propagates towards a distant target where it is partially reflected or back-scattered before being re-injected into the active cavity of the laser. When the laser diode experiences the external optical feedback, the reflected light imprinted with information from the distant target or from the external cavity medium induces perturbation to the operating parameters of the laser. For SMI measurement sensors such as harmonic motion and absolute distance applications, the fringe counting method is basically used to determine the target's displacement and distance respectively. Two different approaches to modelling the SMI phenomenon have been developed: the three-mirror cavity and the perturbation of the rate equation. The single equation that describes the phase condition imposed by the optical feedback is usually referred to as the excess phase equation. One of the most important and most useful parameters in the excess phase equation is the feedback parameter C as it can be used to qualitatively categorize the regime of the laser under optical feedback. When the feedback level C 1, the laser behaviour is stable. On the other hand, when the feedback level C 1, more complex phenomena are observed such as hysteresis effect, presence of multiple emission frequencies (including the unstable frequencies), apparent splitting of the emission line due to mode hopping and fringe disappearance phenomenon. The fringes disappearance phenomenon in the self-mixing interferometry occurs whenever the external round-trip phase at free-running state is modulated by either external modulation such as external cavity length changes or internal modulation when the laser injection current is modulated with a high back-scattered light power. This phenomenon has been observed by many authors for harmonic motion or vibration application and more recently in the case of the absolute distance measurement scheme when the laser injection current is modulated in the triangle waveform. This phenomenon is highly dependent on the feedback parameter C and it is described in detail based on the coupled cavity model. The primary cause for fringes disappearance is demonstrated to be the expansion of the excess phase equation stable solutions range with the increment of the parameter C, thus reducing the number of stable solutions for a given phase stimulus. This new approach in the modelling of the fringe disappearance phenomenon allows determination of the C values for which a pair of fringes are expected to disappear and as a consequence correlates the number of missing fringes to the value of C. This approach is validated both by a behavioural model of the laser under optical feedback and by a series of measurements in the SMI absolute distance configuration.
Download or read book Semiconductor Lasers written by Junji Ohtsubo and published by Springer. This book was released on 2017-05-03 with total page 679 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in semiconductor lasers are discussed, but also for example the method of self-mixing interferometry in quantum-cascade lasers, which is indispensable in practical applications. Further, this edition covers chaos synchronization between two lasers and the application to secure optical communications. Another new topic is the consistency and synchronization property of many coupled semiconductor lasers in connection with the analogy of the dynamics between synaptic neurons and chaotic semiconductor lasers, which are compatible nonlinear dynamic elements. In particular, zero-lag synchronization between distant neurons plays a crucial role for information processing in the brain. Lastly, the book presents an application of the consistency and synchronization property in chaotic semiconductor lasers, namely a type of neuro-inspired information processing referred to as reservoir computing.
Download or read book Self mixing Interferometry with Vertical cavity Surface emitting Lasers written by John Tucker and published by . This book was released on 2010-02 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electro Optical Instrumentation written by Silvano Donati and published by Pearson Education. This book was released on 2004-04-09 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: The complete, practical sourcebook for laser sensing and measurement This is a systematic, up-to-date guide to laser instrumentation for sensing and measurement in contemporary scientific, industrial, automotive and avionics applications. Dr. Silvano Donati presents clear design rules and useful hints for practical implementation of a wide variety of laser instruments. For each type of instrument, the author outlines basic principles, physical limitations, reasonable performance expectations, optical design issues, and electronic signal handling--illustrated with block schemes. Coverage includes: Interferometers for sub-micrometer displacement measurements Nanometer vibrometers and structural integrity testing Doppler velocimeters for anemometry of fluids Range finders and anti-collision systems Non-contact wire-diameter and particle-diameter sizing Alignment and level meter apparatuses Ring laser and optical fiber gyroscopes Optical fiber sensors Thorough and accessible, Electro-Optical Instrumentation offers balanced coverage of both optical and electronic issues and challenges. It will give working electronic engineers and scientists the knowledge they need to design virtually any electro-optical instrumentation system. PRENTICE HALL Upper Saddle River, NJ 07458 www.phptr.com
Download or read book Basics of Interferometry written by P. Hariharan and published by Academic Press. This book was released on 2012-12-02 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is for those who have some knowledge of optics, but little or no previous experience in interferometry. Accordingly, the carefully designed presentation helps readers easily find and assimilate the interferometric techniques they need for precision measurements. Mathematics is held to a minimum, and the topics covered are also summarized in capsule overviews at the beginning and end of each chapter. Each chapter also contains a set of worked problems that give a feel for numbers.The first five chapters present a clear tutorial review of fundamentals. Chapters six and seven discuss the types of lasers and photodetectors used in interferometry. The next eight chapters describe key applications of interferometry: measurements of length, optical testing, studies of refractive index fields, interference microscopy, holographic and speckle interferometry, interferometric sensors, interference spectroscopy, and Fourier-transform spectroscopy. The final chapter offers suggestions on choosing and setting up an interferometer.
Download or read book Implementation of Differential Self mixing Interferometry Systems for the Detection of Nanometric Vibrations written by Francisco Javier Azcona Guerrero and published by . This book was released on 2018 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Thesis, we explore Self-mixing interferometry (SMI ), a method capable of producing high resolution optical path related measurements in a simple, compact and cost-effective way. Even with a notably less complex setup than traditional interferometric methods, SMI can produce measurements with a resolution well below the micrometric scale (N'2) which is sufficient for most industrial applications. The SMI effect is produced when a small part of the laser power impacting a target is back-scattered and re-injected into the laser cavity. As a result, the phase and amplitude of the laser wave is modified generating a signature beat, which can be "easily" related to different optical path-related dynamics. The main advantage of this method in relation to other interferometric methods is the simple setup consisting mainly of a single mode laser diode (LO) equipped with a simple electronic system readout a simple optical system may be used to collimate/focus the beam allowing measurements at larger distances. Because of the small amount of reflected optical power required to allow the effect, the technique can produce high resolution measurements even with diffusive targets. While the SMI method has been largely studied in the last three decades, there are still several topics worth the development of further research. One of those topics, how to increase the resolution on displacement measurements, is one of the main topics covered in this work. Classical SMI methods allow the reconstruction of displacement measurement with a resolution of N'2. The use of special processing algorithms can push further this limit reaching values in the order of e.g. N32. In this work, we propose a method to increase even further this limit reach values better than N100.The idea discussed, differential self-mixing interferometry (OSMI) proposes the use of a reference modulation (mechanical or electrical) to be used as a reference for the measurement. Simulated results have shown that under ideal conditions, it may be possible to reach resolutions in the order of N1000. In practice, however, this limit is much smaller (N100) because of LO dynamics, and different practical limitations present in the amplification and readout electronics. Experiments and measurements are presented along the second chapter of this work to present proof of the proposed method. After exploring the basics of OSMI, possible applications for classic SMI and DSMI were pursued. The obtained results are presented in the following sections. First, a review on potential biomedical measurements using SMI is discussed. The obtained results suggest that it is possible to obtain some key values related to biomedical constants (e.g. P.PW) using a displacement SMI measurement. The method, however, may not be reliable enough especially on long time measurements. Moreover, the use of certain wavelengths must be avoided during long exposures as they may prove harmful to the soft tissue due to the requirements of a small laser spot. lt is observed that SNR may lead to difficulties during the signal processing stage which may impact the results of the reconstructed signal. Next, the DSMI method was tested in an AFM-like cantilever system. The results suggest that is possible to follow the motion of a micrometric size cantilever oscillating at low frequencies with a high resolution. Higher frequencies may be achieved by using an electronic reference modulation configuration. The proposed system was able to detect some artefacts on the motion which maybe attributed to possible deflections on the cantilever surface. Possible enhancements to the method are suggested for any researcher who wants to expand the topic.
Download or read book Interferometry in Speckle Light written by P. Jacquot and published by Springer Science & Business Media. This book was released on 2012-02-02 with total page 661 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings reflect the work presented at the conference "Interferometry in Speckle Light: Theory and Applications", held at the Ecole Polytechnique Federale de Lausanne, (EPFL), the Swiss Federal Institute of Technology in Lausanne, Switzerland. The event took place from September 25 to September 28, 2000. Thanks to the diligence of the authors, this book has been published just in time for the conference. Writing this preface in July, in anticipation of the conference, we have tried to envisage how this book will benefit the quality of discourse between authors and attendees. "Interferometry in Speckle Light: Theory and Applications" results from a bottom-up approach and is original in several ways. This conference is not part of a series; on the contrary, it is a single event. The idea of gathering scientists and engineers for a general discussion on the theory and the practice of interferometry, involving rough, non-optically polished objects, was "in the air". An opportunity of this sort was not provided by any of the conferences scheduled when the present one was conceived. For this reason, it was easy to convince a small number of renowned researchers, all of them active in the field of holographic and speckle interferometry, to organize a conference. To be specific, they are the people listed below as members of the scientific and local committees. At the same time, a particular circumstance, namely the retirement of Professor L. Pflug, helped to detennine the location of the meeting.
Download or read book Methods and Devices for Optical and Electrical Metrology with Application to Phase shifting Interferometers Torsional Microstructures and Levitated Accelerometers written by David Gordon Garmire and published by . This book was released on 2007 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Interferometers written by David Halsey and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An interferometer is a device that splits a beam of light into two beams. In this book, the most prominent active interferometers are discussed from a research point of view focusing on three variants. Among the many topics of research included in this book are: results of adaptive interferometers operation based on photorefractive crystals and the effect of the non-steady state photo-electromotive force, a reanalysis of the framework of the "magnetic" components of gravitational waves, the development of a real-time in situ surface height measuring system based on phase shifting interferometer, a review of a single-channel interferometer for generating digital Fresnel holograms of 3-D real-existing objects illuminated by incoherent light, a study on the volumetric changes which occur during photopolymerization under nonisothermal conditions and a discussion of the electrochemical Koesters interferometer technique used for the determination of changes of surface stress of solid electrodes. In order to cope with the unceasing bandwidth demand fueled by the massive use of the Internet, this book includes a review of the two main types of switching devices, namely the SOA-assisted Sagnac switch(TOAD) and the Ultrafast Nonlinear Interferometer. Application of Laser interferometry technique for investigation of acoustic wave fields is considered as well.
Download or read book An Introduction to Self mixing Interferometry with an Application to Vibrometry written by Matthew L. O'Donnell and published by . This book was released on 2008 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interferometry written by Bruno Ullrich and published by . This book was released on 2019-08-28 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors provide an overview of recent developments in the field of interferometry. To achieve this aim, a broad range of topics is presented by experts who have summarized recent results drawn from theory and experiments. The simplicity and versatility of interferometry technique can be easily seen in the broad range of problems discussed in the text. This important book project presents recent, unique updates on interferometry.
Download or read book Interferometers written by Kystal Harmon and published by Nova Science Publishers. This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents readers with the latest research in interferometry. Chapters include research done on an approach that can be used to identify the performance of coherence scanning interferometers in the presence of vibration; the permeability engineering of semiconductor photonic devices; several interferometric structures based on bulk optics to achieving optical interleaving; interference lithography; recent results on laser surface patterning using interferometers and femtosecond laser radiation; the realisation of the optical interferometers with the optical MEMS technology; a simple two-ray interferometer tuned by rotation; tuning of interference pattern period by rotation of an interferometer itself; the characteristics of a two-ray interferometer with fixed mirrors; the detection of acoustic fields from bounded ultrasonic beams by using laser interferometry techniques; and the use of lateral shearing interferometry as an important area of general interferometry.
Download or read book Self mixing Interferometry and Its Applications in Noninvasive Pulse Detection written by Jukka Hast and published by . This book was released on 2003 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fringe Pattern Analysis for Optical Metrology written by Manuel Servin and published by John Wiley & Sons. This book was released on 2014-08-18 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this book is to present the basic theoretical principles and practical applications for the classical interferometric techniques and the most advanced methods in the field of modern fringe pattern analysis applied to optical metrology. A major novelty of this work is the presentation of a unified theoretical framework based on the Fourier description of phase shifting interferometry using the Frequency Transfer Function (FTF) along with the theory of Stochastic Process for the straightforward analysis and synthesis of phase shifting algorithms with desired properties such as spectral response, detuning and signal-to-noise robustness, harmonic rejection, etc.
Download or read book Optical Metrology written by Kjell J. Gåsvik and published by John Wiley & Sons. This book was released on 2003-04-11 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: New material on computerized optical processes, computerized ray tracing, and the fast Fourier transform, Bibre-Bragg sensors, and temporal phase unwrapping. * New introductory sections to all chapters. * Detailed discussion on lasers and laser principles, including an introduction to radiometry and photometry. * Thorough coverage of the CCD camera.
Download or read book Modern Interferometry for Length Metrology Exploring Limits and Novel Techniques written by René Schödel and published by Institute of Physics Publishing. This book was released on 2018-12-21 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern Interferometry for Length Metrology: Exploring limits and novel techniques gives an overview of refined traditional methods and novel techniques in the field of length and distance metrology. Within the book advanced solutions, which can be used for various applications and can help provide a comprehensive understanding of both metrology and interferometry, have been developed and discussed.
