Research and Application of Measurement System Base on Laser Self-Mixing Interference

激光自混合干涉效应是指由于外部物体反射或者散射，而导致光反馈回激光腔内引起光功率波动的现象。该技术不仅保证了传统干涉的测量精度，还具备单光路、结构紧凑、易准直等优点，解决了传统干涉中存在的问题，因此受到了研究人员的关注，被广泛应用于速度、位移和振动、生物医学等领域的测量。 本文介绍了激光自混合干涉效应的发展历程和研究现状。通过三种不同的数学模型，详细阐述了自混合效应的机理，并对自混合干涉系统进行数值仿真，进而分析研究了系统模型中各参数对自混合干涉信号的影响。在此基础上，搭建半导体激光器自混合干涉测量系统，通过观察和研究实验现象，验证了理论仿真的结果。此外，本文还根据自混合基本数学模型，研究了...As a new laser technique called, self-mixing interference (SMI), which is based on the interaction of cavity field with the field backscatter from the remote target, has increasingly garnered intense attention. The SMI has advantages of simple and compact system structure and easy collimated light path. Therefore, the applications of the SMI have been popularized in many fields, including metrolog...学位：工学硕士院系专业：信息科学与技术学院_光学工程学号：2312013115309

Noise Decrease in a Balanced Self-Mixing Interferometer: Theory and Experiments

In a self-mixing interferometer built around a laser diode, the signals at the outputs of the two mirrors are in phase opposition, whereas noise fluctuations are partially correlated. Thus, on making the difference between the two outputs, the useful signal is doubled in amplitude and the signal-to-noise ratio is even more enhanced. Through a second-quantization model, the improvement is theoretically predicted to be dependent on laser facets reflectivity. The results are then validated by experimental measurements with different laser types that show very good agreement with theoretical results. The new technique is applicable to a number of already existent self-mixing sensors, potentially improving significantly their measurement performances

Chest Expansion Measurement in 3-Dimension by Using Accelerometers

The chest expansion measurement is a part of physical therapy to track the progress of rehabilitation for checking the performance of lungs. The chest expansion mechanism moves like pump handle and bucket handle. These two movements cause the chest move many directions. For tracking the chest movement in each direction, the MEMS accelerometers are used to measure acceleration in each axis. Consequently, acceleration is converted to displacement by double integration. The acceleration from accelerometer in each axis is affected from the earth gravity force. Thus, rotation matrix is used for compensating the earth gravity force. It can track the acceleration vectors while rotating. The known movement from robot is simulated similar the chest expansion. 60 sets of accelerometer data were collected from robot demonstration and were analyzed for testing the accuracy of sensor and algorithm. For the highest expansion, the chest expansion measurement must be performed while doing deep breathe inhale and exhale. The deep breath signal is a low frequency and there is high frequency noise. Therefore, a low-pass filter was used for eliminating high frequency noise. The accelerometers and VICON’s markers were placed together on the body. The displacement results from accelerometers were compared with the displacement of VICON motion analysis system to find the accuracy of our purposed device. The average error of 20 sets of acceleration data from accelerometers which referred with VICON motion analysis is 7.195±4.361 mm. Accelerometer result trend follows VICON motion analysis and corresponds to each other

Advanced Knowledge Application in Practice

The integration and interdependency of the world economy leads towards the creation of a global market that offers more opportunities, but is also more complex and competitive than ever before. Therefore widespread research activity is necessary if one is to remain successful on the market. This book is the result of research and development activities from a number of researchers worldwide, covering concrete fields of research

Analysis and implementation of algorithms for embedded self-mixing displacement sensors design

L'interaction entre un faisceau laser émis avec une partie de la lumière réfléchi depuis une cible qui rentre dans la cavité active du laser, est à l'origine du phénomène de rétro-injection optique ou self-mixing. L'utilisation de ces franges interférométriques non conventionnelles, semble attractive du au faible nombre des composant optiques et son caractère auto-aligné. Dans cette thèse nous approchons leur développement en tant qu'implémentation embarqué rentable pour la mesure du déplacement. A cette fin, nous avons exploré des méthodes du traitement du signal pour la détection des franges et la reconstruction du mouvement de la cible, en évitant l'usage de composant externes. Premièrement, nous avons identifié quelques incompatibilités dans des algorithmes précédentes établis dans notre centre de recherche, puis nous avons avancé des solutions. Fondé sur la théorie d'interpolation, an algorithme simplifié mais démontré convenable en temps-réel à été proposé pour la reconstruction du déplacement. En s'appuyant sur l'élaboration d'un signal analytique, il à été proposé une version amélioré pour le calcul de phase. Celle-ci nous à permit de fournir un algorithme pour la détection de franges, robuste aux variations d'amplitude, sans tenir compte du régime de rétro-injection, impliquant une convenable utilisation pour une variété d'applications. ABSTRACT: The interaction between an emitted laser beam and a small portion of backscattered light from a pointed target that re-enters the laser's cavity, is at the origin of optical feedback phenomenon or self-mixing. Exploiting these unconventional interferometric fringes for non-contact sensors is attractive due to its minimal optical part-count and self-aligned nature. In this thesis we approach its development as a cost-eective embedded implementation for displacement measurement. To this end we explored signal processing methods for fringe detection and target's movement reconstruction, avoiding the usage of external components. We first identified some incompatibilities in prior algorithms from our research center, and then proposed further solutions. Based on interpolation theory, a simplified but proved real-time algorithm resulted for displacement reconstruction. Relying on analytical signal elaboration, an improved approach for phase calculation allowed us to provide a fringe detection algorithm robust to amplitude variations, disregarding the feedback regime and thus, allowing a seemly usage over an increased variety of applications

Optical coherence tomography: applications and developments for imaging in vivo biological tissue

In this thesis the design and build of a high-speed, video-rate optical coherence tomography (OCT) imaging system is described. The system was designed for the purpose of imaging human skin in vivo, particularly that of patients suffering from conditions such as systemic sclerosis. Component selection and design decisions are discussed in the context of the intended final application. Initial test images from the system are presented. In the context of building an OCT system, a supercontinuum light source was characterised and tested for its suitability for use in the OCT environment. Parameters such as coherence length were measured using simple interferometry techniques, while practical considerations such as portability and ease of system integration were also considered.Several applications of OCT imaging techniques were also investigated, using two commercially-available OCT systems from Thorlabs, Inc. A liquid-based skin and blood flow model was constructed using narrow glass capillary tubes, pumped through with scattering solutions of Intralipid or suspensions of polystyrene microspheres. The concentration of the solutions was tuned by dilution in order to best model the scattering parameters of blood. The model also used similar liquid solutions to model static tissue surrounding the blood vessels. Doppler OCT images of the model under various conditions were recorded, and velocity profiles of the flowing liquids were extracted.Using the same commercial OCT systems, imaging over two separate wavelength regions was also performed on the skin of several different species of neo-tropical tree frog, some of which have interesting reflective properties due to the presence of a pigment called pterorhodin. Cross-sectional OCT images of the skin are presented, and averaged depth profiles extracted from them. This is the first time that OCT imaging has been applied to this problem.A clinical study of skin thickening and microvascular function in patients with systemic sclerosis compared to healthy controls was also carried out, again involving a Thorlabs, Inc. commercial OCT system. This study was carried out at Salford Royal Hospital under the supervision of the rheumatology research group. Skin thickness was assessed using OCT and high-frequency ultrasound imaging. Microvascular function was measured using nailfold cappilaroscopy and laser Doppler imaging. Images from the study are presented here.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Methods for Doppler Radar Monitoring of Physiological Signals

Unobtrusive health monitoring includes advantages such as long-term monitoring of rarely occurring conditions or of slow changes in health, at reasonable costs. In addition, the preparation of electrodes or other sensors is not needed. Currently, the main limitation of remote patient monitoring is not in the existing communication infrastructure but the lack of reliable, easy-to-use, and well-studied sensors.The aim of this thesis was to develop methods for monitoring cardiac and respiratory activity with microwave continuous wave (CW) Doppler radar. When considering cardiac and respiration monitoring, the heart and respiration rates are often the first monitored parameters. The motivation of this thesis, however, is to measure not only rate-related parameters but also the cardiac and respiratory waveforms, including the chest wall displacement information.This dissertation thoroughly explores the signal processing methods for accurate chest wall displacement measurement with a radar sensor. The sensor prototype and measurement setup choices are reported. The contributions of this dissertation encompass an I/Q imbalance estimation method and a nonlinear demodulation method for a quadrature radar sensor. Unlike the previous imbalance estimation methods, the proposed method does not require the use of laboratory equipment. The proposed nonlinear demodulation method, on the other hand, is shown to be more accurate than other methods in low-noise cases. In addition, the separation of the cardiac and respiratory components with independent component analysis (ICA) is discussed. The developed methods were validated with simulations and with simplified measurement setups in an office environment. The performance of the nonlinear demodulation method was also studied with three patients for sleep-time respiration monitoring. This is the first time that whole-night measurements have been analyzed with the method in an uncontrolled environment. Data synchronization between the radar sensor and a commercial polysomnographic (PSG) device was assured with a developed infrared (IR) link, which is reported as a side result.The developed methods enable the extraction of more useful information from a radar sensor and extend its application. This brings Doppler radar sensors one step closer to large-scale commercial use for a wide range of applications, including home health monitoring, sleep-time respiration monitoring, and measuring gating signals for medical imaging