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kavehvash--zahra
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Design, Simulation and Image Reconstruction in Frequency-scan Millimeter-Wave Imaging System
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Frequency-scan millimeter-wave imaging systems are of high interest due to their low cost and acceptable performance in many applications such as concealed-weapon-detection. In recent years, the performance of this system in view of imaging time, image quality and cost has been improved via its implementation based on metamaterial apertures. These structures take advantage from the famous theory of single pixel imaging in optics. Through using the compressive sensing principle, the number of required imaging modes for obtaining diffraction limited resolution is reduced which in turn lessens the imaging time and more importantly the required bandwidth. Still, the image quality and resolution...
Modified Computed Tomographic Imaging Systems with Improved Reconstructed Image Quality
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Computerized tomography (CT) imaging is a powerful tool among the existing bio-imaging techniques for capturing bio-images. In a CT scan procedure, linear sensors receive x-ray radiations, passed through the patient’s body and the reconstruction algorithms provide the required image for physicians from the captured data. In spite of its great advantages, due to the use of x-ray radiations and its ionization effect, it will raise the risk of cancer in long times. Therefore, to take benefit from several advantages of CT such as low-cost and high speed, solving this problem is aimed by many physicians and scientists. A new compressed sensing-based algorithm in order to reduce the number of...
Using Nonlinear Effects of Light for Optical Signal Processing
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the...
Temporal Optical Signal Processing Based on Light Dispersion
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Spatial-temporal duality is considered vastly as a powerful technic to process optical signal fast. Band-width and sampling rate are bottlenecks in real time capturing and processing of optical signals by analog to digital converters. There have been tremendous efforts in the field of optical processing in order to enhance the speed of processing or quality of optical beams. Another successful method in high speed processing of optical signals is the improvement of time-bandwidth product by applying group delay engineering. In this research I did my best to overcome the inherent restriction of band-width of imaging systems exploiting concepts of time lens and time prism in such a way that...
Temporal Depth Imaging Based on Dispersion
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
In this thesis, the aim is designing an optical temporal imaging system. In recent years, due to many applications, including the receipt of high-rate data by slow receivers and compensation of dispersion in telecommunication systems, researchers have considered the topic of temporal imaging. This field of research is based on dispersion, electro-optical modulators or time lenses and space-time theory. By modeling dispersion properties as a depth dimension and taking ideas from three-dimensional spatial imaging systems we intended to increase the temporal resolution and depth of focus of the structure. We also present a novel technique for multiplexing and demultiplexing telecommunication...
Improvement of Image Quality in Photoacoustic Imaging Based on Synthetic Aperture Techniques
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Photoacoustic imaging is one of the nascent imaging methods that has received a lot of attention in the last two decades. There are two major imaging challenges with this method, including the finite size of the transducer element and the limited view angles of the photoacoustic tomography arrangement. To compensate for the effects of finite transducer size, we have proposed a multi-angle detection method for circular photoacoustic imaging systems based on the synthetic aperture techniques, in the proposed method, each transducer, in addition to rotating around the scan center, also has a rotation in the around its center. This rotation depends on the cut-off frequency, the diameter of the...
Time Domain Optical Signal Processing Based on the Duality Between Dispersion and Diffraction
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
In the last decades, due to the growing demand of transferring information with high transmission rates, the complexity and development of telecommunication and optical systems is remarkable. Researchers around the world attempt to explore extraordinary potential of light to process information. In the mid-19th century, scientists discovered a mathematical symmetry between the spatial and temporal optics fields, which originated from the similarity of equations governing the paraxial diffraction of beams and the dispersion of narrow-band pulses known as space– time duality in scientific texts. This new approach provides more advanced and potent methods to temporal processing and...
Image Resolution Improvement in a Photoacoustic Imaging System based on Beamforming
, Ph.D. Dissertation Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
The fast-growing development of engineering and medical sciences leads to the diagnosis and treatment of diseases with higher accuracy and in the early stages of the disease. Medical imaging systems are considered as a crucial and effective tool in this field that based on the principle of technology used, are able to image various tissues with high quality. In recent years, photoacoustic imaging has attracted the attention of many researchers and engineers, because it able to image different tissues with good resolution and penetration depth non-invasively and without the use of ionizing radiation. The photoacoustic system response is a low-pass filter that passes only low-frequency...
Upgrading the Ultrasound Imaging System Based on The Implementation of the Strain Imaging Mode
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Strain imaging is a non-invasive ultrasound modality for assessing cardiac function in echocardiography systems. In this thesis, we implemented a fully automated strain imaging system containing 5 steps: 1) echocardiographic view recognition, 2) cardiac cycle phase detection, i.e., the events of end-diastole (ED) and end-systole (ES), 3) segmentation of left ventricular (LV) myocardium, 4) motion estimation of this wall and 5) strain calculation. In this work, we propose a novel deep learning-based framework for phase detection of cardiac cycle by the use of echocardiographic images in multibeat videos. Further, by applying the augmentation technique, the model has been able to detect events...
Modification of Biomedical Imaging Methods in Short Wavelength Infrared Window
, Ph.D. Dissertation Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
In recent years, optical biomedical imaging techniques show great potential in noninvasive imaging. Although these methods have many advantages over other biomedical imaging methods (such as Computerized Tomography (CT), Magnetic Resonance Imaging (MRI) and etc.), these techniques confront with some problems such as optical scattering, light absorption and etc. For in vivo imaging, the short-wavelength infrared region (SWIR; 1,000–2,000 nm) provides several advantages over the visible and near-infrared regions: general lack of auto-fluorescence, low light absorption by blood and tissue, and reduced scattering. In this thesis we want to analyze the traditional IR imaging techniques and...
Imaging Through a Scattering Medium Using Microwave Frequency
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Radio waves can penetrate through walls and various scattering environments, allowing us to communicate with mobile phones within buildings or use wireless waves to transfer data from one room to another despite physical obstacles. Radio signals, especially at lower frequencies, are highly effective in traversing such environments. However, the ability to penetrate walls does not imply the ability to "see through" them. In this thesis, we focus on examining the development and improvement of imaging techniques in the presence of walls. The aim is to present the concept of imaging through walls in a comprehensible manner for researchers and enthusiasts, facilitating the development and...
Performing an Efficient Architecture for Compressive Sensing Algorithms in CT Application
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Co-Advisor)
Abstract
Computerized tomography (CT) is a powerful tool among existing bioimaging techniques for capturing bio-images. In fact, CT imaging systems have attracted great attention in the last decades, because of their fast and high-quality reconstruction, low complexity and low-cost hardware solutions. In a CT scan procedure, linear sensors receive x-ray radiations, passed through the patient’s body and The quality of the reconstructed image is essentially influenced by the number of captured line projections. Nevertheless, gathering the adequate amount of data requires the patient to being exposed to X-ray radiations for a long time. However, the intensification of x-ray radiations could lead to...
Design and Implementation of X Band CMOS Vector Modulator
, M.Sc. Thesis Sharif University of Technology ; Medi, Ali (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
In this thesis, an X band vector modulator chip in CMOS .18 um technology is designed, implemented and measured. The receiver with two RF signal path includes differential amplifier, hybrid, attenuaters, variable gain amplifiers (VGA) and power combiner blocks respectively. Capability of gain and phase control is provided by 14 digital bit. 6 bits are used to control gain of each RF path, so that changing the phase and gain of the output signal in a trigonometric quarter shall be possible. The trigonometric quarter is selected by two single pole double throw switch. Cascode structure is utilized in amplifiers stages for its stability and isolation feature. Furthermore, in order to to enhance...
Modeling, Design and Efficient Low-Cost Digital Implementation of Millimeter-Wave Imaging System
, Ph.D. Dissertation Sharif University of Technology ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Co-Supervisor)
Abstract
Recently, there has been an increasing trend towards the use of millimeter-wave (MMW) imaging in various detection applications. This is mainly due to two factors: first, the radiation in the MMW band (30–300 GHz) is nonionizing and safe to use and second, it is able to penetrate through most dielectric materials as well as poor weather conditions, such as smoke and fog. With these potentials, MMW imaging has been used in a variety of applications, including target surveillance and precision target imaging, safe aircraft landing, highway traffic monitoring in fog, remote sensing for civil applications and concealed threat object detection for security concerns. Moreover, it can also find...
Study and Analysis of the Amount of Three-Dimensional Image Resolution Improvement Achievable By Incoherent Holography
, M.Sc. Thesis Sharif University of Technology ; Mehrani, Khashayar (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
New technologies for three-dimensional (3D) sensing and visualization of real-world objects have been pursued by scientists and engineers for many decades. As opposed to traditional two-dimensional (2D) imaging techniques, 3D imaging technologies can potentially capture the 3D structure, range, and texture information of objects. Therefore, it can be developed for many applications, as medical imaging and diagnosis, dentistry, industrial designs, architecture and security. There are many 3D imaging technologies, such as holography, incoherent holography and integral imaging. Since holographic methods are based on the wave interferometry of two coherent beams, they demand high stability of...
Design and Implementation of DNA Pattern Recognition Algorithm Utilizing Optical Coding Method
, M.Sc. Thesis Sharif University of Technology ; Koohi, Somayyeh (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
In this research, two novel optical methods have been proposed for DNA local sequence alignment. The proposed methods benefit from algorithms and methods in computer field and ability of parallelism in optical wave to achieve a low-cost process and propose an easy understanding output in DNA local sequence alignment procedure. The first method is built upon moiré matching technique which is extended by proposed HAPPOC scheme using amplitude, phase, and polarization of optical wave. For analyzing the extended moiré output, a novel 3D Artificial Neural Network is designed and developed by optical structure. The second structure, as named HAWPOD method, is based on DV-Curve method. The HAWPOD...
Improving Resolution in Lensless Holographic Imaging
, M.Sc. Thesis Sharif University of Technology ; Amini, Arash (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
High-resolution microscopy with the high field of view is necessary for a lot of applications related to medical studies in different areas and to reach this goal, Imaging Systems with high space bandwidth is required. Since CMOS and CCD image sensors are used for capturing digital images, the large amount of studies has been dedicated to optics and signal processing in order to achieve high resolution and the high field of view images.In lens-based imaging systems, large space-bandwidth is achieved through large lenses with higher magnification and larger image sensors with more number of pixels. The drawback of this methods is using larger optic components that lead to increased cost and...
Implementation of a Millimeter Wave Imaging Algorithm Based on Compressed Sensing
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Co-Advisor)
Abstract
Recently, millimeter wave imaging (MMWI) technology is given more attention. This is as a result of three facts. First, despite the infrared or optical cameras, these systems can image a target, which is obscured by one or more optically barriers. Second, the electronics circuits in this band have seen great achievements in the current decade, which facilitate the implementation of MMWI structures. Third, there is no known health hazard for the systems operating in this band with moderate power. Therefore, in this project, a MMWI system based on compressed sensing (CS) for the concealed weapon detection application is proposed. This design consists of a linear antenna array, an appropriate...
Implementation of Millimeter-wave Imaging Algorithm Based on Frequency Scanning Antenna
, M.Sc. Thesis Sharif University of Technology ; Shabani, Mahdi (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
Nowadays millimeter wave imaging technology has found various applications in industry, medical and security systems. From one side the capability of penetration of this frequency spectrum into non-metal objects, and being harmless to humankind on the other side, has made this spectrum an appropriate alternative instead of dangerous spectrums such as X-ray. Recently, development of millimeter wave electronic circuits and antenna arrays has made the optimal design and implementation of millimeter wave imaging systems feasible. Among actions which have been taken in industry, medical and security systems until now, we can refer to efforts for detection of defects in production line,...
Implementation of an Efficient Image Reconstruction Algorithm in Multi-Static MillimBey ter Wave Imaging
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor) ; Kavehvash, Zahra (Supervisor)
Abstract
Nowadays, electromagnetic waves with millimeter wavelengths have various usages including medical,non destructive testings, structure inspection and imaging usages. Millimeter waves go through most of common clothings, but unlike x-ray waves, these waves have no ionizing effects.Therefore, they have low health risks for humans. This characteristic makes the imaging systems based on millimeter wave suitable for security purposes, such as airport security. The inclined usage of these systems requires an increase in precision, speed, reduction of error and automatic object detection algorithms. An important way to increase precision is to change the imaging system structure, resulting in...