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Phase-extraction from fringe patterns is an inevitable procedure in many applications, such as interferometry,Moiré analysis, and profilometry using structured light illumination. However, speckle noises could be introduced when a coherent light source is used. In this thesis, we use the empirical mode decomposition (EMD) to perform the speckle-reduction. It is found that phases can be extracted with high accuracy once speckle-reduction is performed with the EMD.

Optical interferometric techniques are being increasingly used in industry. These non contact techniques, using laser methods based on speckle interferometry, assure a greater accuracy in measuring displacements caused by deformations. One such technique, Electronic Speckle Pattern Interferometry (ESPI), has been used successfully, by analysis of the reaction of mechanical components to induced mechanical or thermal stress, for the measurements of in-situ, real time, full-field, in-plane and out-of-plane displacements and the detection of detachments, micro-cracks occurring as internal and external defects.

Phase-extraction from fringe patterns is an inevitable procedure in the field of optical metrology and interferometry. However, speckle noise will introduce and influence the precision of wrapped phase map when a coherent light is used. In this thesis, we use the bidimensional empirical mode decomposition (BEMD) to perform the speckle-reduction. Moreover, different interpolation method in BEMD will be used to compare their performance in speckle-reduction. Finally, the database will be developed to make the BEMD a robotic tool to reduce noises. And the database also points out that the performance of BEMD is highly related to the fringe period, the fringe visibility, and the SNR of speckle noise.

A projected fringe profilometry (PFP) is a wide optical measurement technology to gauge the three dimensional appearance of object.Because of non-contact type , the short retrieve time and low environmental effect,PFP was usually used in many fields.PFP has become rather efficient and precise on gauging the three dimensional appearance of the static obiect because of its persistent development in recent years.However,it is still not mature yet to gauge the dynamic object. If we could develop a gauging way in the dynamic object , the application would be more widespread. First of all,using PFP as the gauging principle and utilzing the math algorithm for analyzing the changes between the dynamic measured object and the blurred fringes.Secondly,reconstructed the inspected object's three dimensional appearance and the velocity. Finally,found out the deformation of the measured object. The technology of this thesis broke through the typical measurement of velocity.We could analyze the velocities of three dimentional dirtions by only single optic imformation.

This thesis describes the design, construction and testing of a new interferometer for the absolute measurement of length standards. It is assumed that this study mainly formed of three parts. Firstly, it starts with an introduction to the subject of length standards and length measurement by interferometry. The design of the new interferometer is given in detail, including the stable lasers used as light sources, fiber, optical and opto-mechanical components. In the second part of this study, the mechanical construction of the interferometer chamber is presented with temperature stabilization and controlling system. The temperature variations inside the chamber at different points in air and along the surface of the length standard are given. After that, the techniques for measurement of the refractive index of the air inside the interferometer chamber are summarized. In the last part of the thesis, a review of fringe analysis techniques is given, with an emphasis on 5 position phase-stepping algorithms. The data processing of images digitized in the interferometer is described, including the techniques developed for discontinuity removal and surface fitting. The measurement of the variation in length and flatness of the measuring faces of the length standards is described and the experimental results are given. The automated method of multiple wavelength-exact fractions is used to combine phase measurements at three wavelengths to allow accurate calculation of the length of the length standards. The experimental results are given for length standards. The uncertainty budget of whole system is calculated and presented in a table.

<p dir="ltr">Monitoring of additive manufacturing (AM) processes allows for saving time and materials by detecting and addressing errors as they occur. When fast and efficient, the monitored AM of each unit can be completed in less time, thus improving overall economics and allowing the user to accept a higher capacity of AM requests with the same number of machines. Based on existing AM process monitoring solutions, it is very challenging for any approach to analyze full-resolution sensor data that yields three-dimensional (3D) topological information for closed-loop real-time applications. It is also challenging for any approach to be simultaneously capable of <i>plug-and-play</i> operation once AM hardware and sensor subsystems are configured. This thesis presents a novel method to speed up error detection in an additive manufacturing (AM) process by minimizing the necessary three-dimensional (3D) reconstruction and comparison. A structured light 3D imaging technique is developed that has native pixel-by-pixel mapping between the captured two-dimensional (2D) absolute phase image and the reconstructed 3D point cloud. This 3D imaging technique allows error detection to be performed in the 2D absolute phase image domain prior to 3D point cloud generation, which drastically reduces complexity and computational time. For each layer of an AM process, an artificial threshold phase image is generated and compared to the measured absolute phase image to identify error regions. Compared to an existing AM error detection method based on 3D reconstruction and point cloud processing, experimental results from a material extrusion (MEX) AM process demonstrate that the proposed method has comparable error detection capabilities. The proposed method also significantly increases the error detection speed, where the relationship between the speed improvement factor and the percentage of erroneous pixels in the captured 2D image follows a power-law relationship. The proposed method was also successfully used to implement closed-loop error correction to demonstrate a potential process monitoring application.</p>

High-resolution three-dimensional (3D) shape reconstruction of objects has huge potential for applications in the field of design, security, entertainment, biomedicine, industrial quality control etc. Of the available techniques, optical methods have the distinctive advantage of facilitating non-contact and non-intrusive measurements. Of late, integration of optical measurement system with the computer based data processing has improved the quality of the results. Of the available techniques, structured-light illumination (Fringe Projection) is the most effective, owing its simplistic experimental architecture and analysis. Traditional Fringe Projection techniques function with the use of fringes generated using interferometric methods. With the advent of digital light projectors, digitally generated fringes have taken the place of interferometry based fringes. Despite the technological advances that this field has witnessed over last couple of decades, digital fringe projection technique still suffers from various shortcomings. This thesis presents a strategic solution to the challenges faced by the technique in its application to out-of-plane deformation measurement of objects under impact loading. First part of the thesis reports the developmental work on building an LED-Grating based optical projection system for implementation of linear-fringe projection profilometry. Successful use of the developed system in measuring out-of-plane deformation experienced by multiple targets under impact loading with a time sapling of 20,000 frames per second is re-ported. However, for performing ballistic impact measurements using the liner-fringe projection method, an order of magnitude higher time-sampling is needed. This is due to the disadvantages associated with linear fringe projection technique: (1) results in wrapped phase map (2p ambiguity) estimation, and (2) the deformation/shift of the recorded fringe pattern in the modulation direction sets a limit on unambiguously measurable whole-plane displacement. Typically, fringe pitch dictates the limit of maximum detectable displacement, and thus to be able to capture larger deformation from the earlier state, coarser fringe pitch is required to be projected; while this adversely affects the resolution of measurement system. Hence, there is a need to develop a fringe projection system which has capability for whole-plane displacement without affecting the resolution and/or necessitating higher temporal-sampling. Circular Fringe Projection (CFP) technique is proposed in the second part of the thesis as a novel solution to address the above issues. CFP technique offers additional advantage of relaxing the temporal resolution requirements of the imaging system by decoupling the maximum measurable deformation rate and the frame rate of camera. A new image analysis method is also developed to extract the underlying phase distribution of the recorded circular-fringe patterns, as the conventionally used single-frame linear-fringe analysis methods are incompetent at demodulating the circular fringes. Experimental results obtained in 3D shape measurement and whole-field out-of-plane displacement measurements of a deforming object reported in this thesis, not only confirms the ability of the proposed CFP technique in overcoming the shortcomings of the widely used linear-fringe projection technique, but also its suitability for deployment in ballistic-impact measurements.

L'étude proposée porte sur l'adaptation d'une méthode de mesure optique à lamesure de la topologie d'objet de grandes dimensions et à une distance de travail proche. Laméthode optique utilisée est la projection de franges car elle permet l'étude de grands objets.Dans un premier temps, des essais expérimentaux ont été réalisés pour évaluer l'exactitudedu développement actuel ; ce dernier utilisant une analyse de franges s'appuyant sur lacombinaison d'une méthode quasi-hétérodyne utilisant une transformation de Fourier etd'une méthode de code gray.Après avoir quantifié les erreurs et déterminé leurs sources, le choix dudéveloppement d'une procédure d'étalonnage et de nouvelles équations associées à cetteprocédure se sont imposés. Le nouvel étalonnage est quant à lui basé sur une interpolationpolynomiale de points définissant un volume de grandes dimensions. Un objet étalon a étéspécialement conçu pour cette procédure de calibration. Pour évaluer l'erreur du à lacalibration, une étude systématique de cas de polynômes dont le plus haut degré varie de 1à 4 a été effectué. Cette approche a permis de déterminer le degré optimal du polynôme àutiliser. Dans le meilleur cas, l'estimation de l'erreur a permis d'évaluer la précision del'étalonnage à 1 mm sur un objet de 2 m évalué à une distance de 2 m.La méthode a été par la suite appliquée, dans un cadre industriel à l'étude deflotteurs et dans un cadre médical à l'étude du relief de la paroi abdominale. D'un point devue médical, cette méthode permet d'obtenir rapidement et facilement la morphologie ducorps humain. Elle permet aussi d'effectuer un meilleur suivi des pathologiesmorphologiques des patients. / The proposed study deals with the adaptation of an optical method to themeasurement of large objects at a low working distance. The optical method used is thefringe projection technique allowing the study of large objects. At first, experimental trials hasbeen used to evaluate the accuracy of the actual development combining the phase shiftingmethod using a Fourier transform and the gray code technique.When the errors have been quantified and their origins determined, the developmentof a calibration procedure and new associated equations have been chosen. The newcalibration is based on polynomial interpolation of points defining a volume of largedimensions. A tested object was designed specifically for this calibration procedure. Toestimate the calibration error, a systematic study of polynomials cases is performed. Thehighest degree of those cases varies from 1 to 4. This approach allows the determination theoptimal polynomial degree to be used. In the best case, the estimation of the error allows theevaluation of the calibration accuracy of about 1 mm for an object of 2 m large, measured ata distance of 2 m.The method has been subsequently applied, in an industrial setting, to the study offloats and in a medical setting to the study of the relief of the abdominal wall. From a medicalpoint of view, this method gives a rapid and easy access to the topology of human body. Itallows a better follow-up of the patient pathology.

<div>Target detection, estimation, and discrimination have long been important research issues in the field of radar. Waveform design, analog signal processing, and digital signal processing are some techniques that can improve the detection, estimation, and discrimination ability. In this dissertation, we first address the sidelobe suppression from the waveform design point of view. We synthesize a non-constant modulus waveform for illumination of radar targets by applying a collection of constant modulus (linear frequency modulated (LFM) waveforms with different frequency offsets) waveforms from each transmitting array element in an antenna array, and we show from the ambiguity function that the non-constant modulus waveform has better performance with respect to the larger ambiguity function mainlobe-to-peak-sidelobe ratio than this ratio of a constant modulus (LFM-only) waveform. Furthermore, from the angular resolution point of view, the synthesized non-constant modulus waveform also has better performance than the angular resolution of a constant modulus waveform at the expense of the decrease in the signal energy on targets.</div><div><br></div><div>Secondly, we investigate radar delay-Doppler resolution enhancement from the digital signal processing viewpoint. We introduce the noise-target fringe analysis technique and combine it with the coherent CLEAN algorithm to provide accurate target parameter estimates in terms of delay, Doppler shift and intensity. Furthermore, the accuracy of target parameter estimates can be further improved by applying weighted non-linear least squares estimation.</div><div><br></div><div>Finally, we further aim for the improvement in radar delay-Doppler resolution. Instead of using the matched filter only, we propose a hybrid filter which combines a chirp matched filter and chirp mismatched filters. The hybrid filter output response shows much better performance in delay and Doppler resolution compared to the chirp matched filter output response. Thus, this hybrid filter design has better target identification capability than the original chirp matched filter. Furthermore, from a real implementation perspective, there is no need to significantly increase the hardware and software complexity of the radar, since we only need to mismatch the received waveform to another chirp waveform and perform some additional non-linear processing. Then a chirp radar system with high delay-Doppler resolution and accurate target discrimination ability can be easily achieved.</div>