Sharif Digital Repository

3D reconstruction of digital images is one of the sub- branches of computer vision which is used in various fields such as computer graphics, compute animation, etc. in general, two approaches exist for solving 3D structure problem. In the first approach to obtain the model, we need a certain distance of the whole object level at a certain point and to do so, a sensor is used which is directly interacting with the object. For instance, we use lasers and estimate the depth using that depth to make 3 D model. In the second approach we use the images we have at different instaces of an object (sensor is the camera that is sensitive to light). Using these data and the machine learning... 

Nowadays, millimeter-wave imaging is widely used in security and medical applications. The growing threat from terrorist attacks is driven research on novel ways to enhance security inspection systems. Millimeter-wave imaging not only is an effective option of penetrating into dielectric materials including cloth, but also provides suitable imaging resolution. Moreover, millimeter-wave imaging is capable of identifying different materials making it a promising option for concealed weapon detection. In spite of X-ray, millimeter-wave imaging is non-ionizing, allowing for non-invasive imaging. In this thesis, first we investigate different millimeter-wave imaging systems and reconstruction... 

Compton imaging is an imaging technique in which Compton scattering is used to produce images from a gamma-ray source. Compton imaging systems are also known as Compton cameras. The basic design of Compton imaging systems consists of two-position detectors that are sensitive to the position and energy scattered from gamma rays. The gamma rays collide with the Compton scatterer detector and the scattered photons are absorbed in the absorber detector. Compton imaging performs well the ground radiation during the scattering processes through the separation of energy. The quality of images produced by Compton imaging depends on a variety of factors including detector energy resolution,... 

Thesedays, personnel surveillance at security checkpoints, such as airports, is becoming increasingly important. Improvements in various fields of imaging techniques provided an attractive opportunity for automatic personnel servaillance at high security checkpoints. Millimeter-wave imaging systems are capable of penetrating through clothes and thin layers to form an image of a person with very high resolution and without no health hazard at moderate power levels. Therefore millimeter-wave imaging is becoming an important method for surveillance purposes. Typically, there are two common methods for microwave imaging, including synthetic aperture imaging and phased-array imaging. Synthetic... 

Millimeter waves provide an effective opportunity to improve vision and imaging in addition to systems based on visible light, X-rays, and infrared, and researchers have paid special attention to the field of millimeter waves to develop imaging. The spectrum of millimeter waves is in the frequency between 30GHz and 300GHz, which is equivalent to the wavelength in free space, between 1 and 10mm. The advantage of millimeter waves is that it works well in different weather conditions. Also, these millimeter waves have the ability to pass through clothing and provide a suitable level of resolution in reconstructed images and provide a suitable ability to separate different materials from each... 

In this thesis, we study image restoration problems, which can be modeled as inverse problems. Our main focus is on inverse problems with Poisson noise; which are useful in many problems like positron emission tomography, fluorescence microscopy, and astronomy imaging. As a popular method in the literature, we use statistic modeling of inverse problem with Poisson noise, in the MAP-estimation framework. Then we introduce a semi-implicit minimization method, FB-EM-TV, that involves two alternate steps, including an EM step and a weighted ROF problem. Then we study well-posedness, existence and stability of the solution. This method can be interpreted as a forward-backward splitting strategy,... 

Acoustic-resolution photoacoustic microscopy (AR-PAM) system can provide 3-D images of facial tissues. The lateral resolution of AR-PAM depends on the numerical aperture (NA) of the acoustic lens and the central frequency of the ultrasonic transducer. There is a trade-off between resolution enhancement and imaging depth. The acoustic beam is tight in the acoustic focal plane but expands in the out-of-focus regions, deteriorating the resolution. High-NA AR-PAM has depth-variant resolution. Synthetic aperture focusing technique (SAFT) based on a virtual detector (VD) concept can compensate for the beam shape and improve the lateral resolution via beamforming. Although, beamforming can enhance... 

Magnetic Resonance Imaging is one of the most advanced medical imaging procedure that noninvasively played in most applications. However, this imaging method is a good resolution, but not in the conventional high speed imaging method, in fact, the main problem is slow. In recent years many studies have been done to accelerate MRI that compressed sensing can be mentioned among them. Such methods, however, have had very good results but MRI systems are very complex. This project investigates the reconstruction of MR images using data from partial non-Cartesian samples aimed at reducing sampling time and also speed up the process of reconstruction of MR images have been studied. In this regard,... 

The conventional cameras and displays do not have the ability to record and display the full brightness of the world around us. These deficiencies have led to the development of methods known as High Dynamic Range Imaging. Most of the work done in this field falls into two groups: compression of the light range and its expansion. In compression, the brightness range is intended to display content with a high dynamic range in simple displays. But the goal of expanding the brightness range is to reconstruct HDR content from a low dynamic range one. In addition to the above classification, this field is also categorized based on the type of content (image or video). In this study, the... 

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... 

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... 

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... 

Millimeter wave imaging systems have unique features and have been used extensively in a variety of applications including medical imaging, construction operations, places with high security such as airports, Nondestructive testing and etc. These systems provide high resolution, due to the order of wavelength which is several millimeter or centimeter in this band. Also in places with high security and for detecting the concealed objects under people’s clothing, these waves can easily pass through the materials and investigate the person’s body without causing health problems. A wide variety of these imaging systems , each with different design parameters and resolutions, have been proposed.... 

In this thesis its considered the characterization of an ultrasound wave in a medium with some obstacles. Derivation of speed of molecules and pressure of the wave is carried out in the Cartesian coordinates system. Simulation is carried out to prove the dependency of wave speed to set up parameters such as the target point (x,y,z) at which the speed value is obtained, the location of the obstacles, the amplitude of original wave emitting from the source, and the propagation speed in different layers of the medium. From the numerical results, it is apparent that the amplitude of the speed wave gets degraded as the wave travels through the medium which is a function of reflection and... 

Increasing advances in millimeter-wave imaging have given the new technology a special place in military and civilian activities. A very important advantage of this imaging system, which has led to its rapid development and growth, is that unlike methods such as X-ray imaging, the millimeter-wave signal is completely harmless to the human body. Because millimeter-wave imaging is non-ionizing, allowing for non- invasive imaging. Also, the millimeter-wave easily passes through human clothing and is reflected when it hits the human body, metal and ceramic objects, and some other objects. As a result, it can be used to photograph underwear, insensitive and safe places such as airports. In this... 

Digital analysis of reservoir rocks prepares a powerful tool in the field of porous media studies and provides appropriate information of single / multiphase flows by performing numerical simulations on porous media images. In order to access the necessary tools to benefit from digital rock analysis and characterization, we need accessing the porous media images, the geometric distribution and the spatial distribution of pores and grains through imaging or reconstruction methods. Porous media reconstruction methods are known as an alternative to imaging techniques. In addition, reconstruction methods have the ability to fix problems and imperfections associated with imaging, such as... 

Nowadays millions of images are shared on social media every day , So image inpainting has become an important issue . After advent of Generative adversarial network image inpainting methodes based on deep learning has been revived and significant progress has been made . For a proper image inpainting , The inpainted image must benefit from the appropriate structure and texture in the missing regions . Therefore, in this project , an attempt is made to use a two-stage structure by using Generative adversarial network .in first stage first by using Gabor filters , the image structure is extracted and then the image structure is completed , while the second stage focuses only on the... 

Sight is probably our most important sense. Every day, humans are exposed to many visual stimuli in their surroundings. The human brain is able to identify and prioritize important and valuable stimuli and memorize them. Identifying and remembering these valuable stimuli is vital to meeting the needs and maintaining survival. The aim of the proposed research is to find the effect of reward learning on the coding of visual objects in the human brain. Previous results have shown that long-term reward-object association make valuable objects more recognizable behaviorally. Studies have also shown that visual stimuli and the pattern of activity of primary visual cortex neurons are closely... 

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... 

Nowadays active Millimeter Wave Imaging Systems are used in verity of medical and security applications. This widespread application re- sults from the intrinsic characteristic of electromagnetic waves in this rang of frequency that can penetrate through interior body structures and clothing with- out bringing harmful ionizing efects to the body. Millimeterwave systems can be very high resolution due to the relatively short wavelength. The current state-of-the-art in active millimeter-wave imaging systems use a set of transmit/receive antennae. The transmitter antennae illuminated the intended person with millimeter waves while the back scattered signal is recorded by the receiver antennae....