Norman S. Kopeika

Bio: Norman S. Kopeika is an academic researcher from Ben-Gurion University of the Negev. The author has contributed to research in topics: Image restoration & Optical transfer function. The author has an hindex of 36, co-authored 371 publications receiving 5221 citations. Previous affiliations of Norman S. Kopeika include Ariel University & University of Pennsylvania.

Feasibility of Radon projection acquisition for compressive imaging in MMW region based new video rate 16×16 GDD FPA camera

Abstract: In this article we present preliminary results for the combination of two interesting fields in the last few years: 1) Compressed imaging (CI), which is a joint sensing and compressing process, that attempts to exploit the large redundancy in typical images in order to capture fewer samples than usual. 2) Millimeter Waves (MMW) imaging. MMW based imaging systems are required for a large variety of applications in many growing fields such as medical treatments, homeland security, concealed weapon detection, and space technology. Moreover, the possibility to create a reliable imaging in low visibility conditions such as heavy cloud, smoke, fog and sandstorms in the MMW region, generate high interest from military groups in order to be ready for new combat. The lack of inexpensive room temperature imaging sensors makes it difficult to provide a suitable MMW system for many of the above applications. A system based on Glow Discharge Detector (GDD) Focal Plane Arrays (FPA) can be very efficient in real time imaging with significant results. The GDD is located in free space and it can detect MMW radiation almost isotropically. In this article, we present a new approach of reconstruction MMW imaging by rotation scanning of the target. The Collection process here, based on Radon projections allows implementation of the compressive sensing principles into the MMW region. Feasibility of concept was obtained as radon line imaging results. MMW imaging results with our resent sensor are also presented for the first time. The multiplexing frame rate of 16×16 GDD FPA permits real time video rate imaging of 30 frames per second and comprehensive 3D MMW imaging. It uses commercial GDD lamps with 3mm diameter, Ne indicator lamps as pixel detectors. Combination of these two fields should make significant improvement in MMW region imaging research, and new various of possibilities in compressing sensing technique.

Restoration and resolution enhancement of a single image from a vibration-distorted image sequence

Abstract: In many applications such as in airborne and terrestrial recon- naissance, robotics, medical imaging, and machine vision systems, the images of a video sequence are severely distorted by vibrations. Super- resolution algorithms are suitable for restoring an image from a low- frequency vibrated sequence because of high correlation between the frames and inherent interframe motion. However, we show that super- resolution algorithms, which were developed for general types of blur, should be adapted to the specific characteristics of low-frequency vibra- tion blur. We demonstrate that in the case of image sequences distorted by vibration, the images should be selected prior to processing. We find empirical selection criteria and propose a selection procedure. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)03309-2) Subject terms: vibration-blurred images; superresolution; iterative back- projection method; vibrations; image restoration; point spread function; optical transfer function.

Restoration of nonlinear motion-distorted composite frame

Abstract: A composite frame image is an interlaced composition of two sub-image odd and even fields. Such image type is common in many imaging systems that produce video sequences. When relative motion between the camera and the scene occurs during the imaging process, two types of distortion degrade the image: the edge 'staircase effect' due to the shifted appearances of the objects in successive fields, and blur due to the scene motion during each field exposure. This paper deals with restoration of composite frame images degraded by motion. In contrast to other previous works that dealt with only uniform velocity motion, here we consider a more general case of nonlinear motion. Since conventional motion identification techniques used in other works can not be employed in the case of nonlinear motion, a new method for identification of the motion from each field is used. Results of motion identification and image restoration for various motion types are presented.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optoelectronic Diodes And CCDs In Vacuum

Abstract: Electrical and optical properties of light-emitting diodes and photodiodes can change significantly in vacuum. These changes involve alterations in forward and reverse current-voltage and capacitance-reverse voltage characteristics, time response, spectral characteristics, quantum efficiency, diode ideality factor, etc. Here, attention is centered on alterations in electrical properties of imaging CCDs in vacuum. Such alterations include increased dark signal, increased responsivity at longer wavelengths in particular, and non-linearity of response.

Glow discharge detector for terahertz and millimeter wave radiation detection and imaging

Abstract: Glow discharge plasma, deriving from direct current gas breakdown, was investigated in order to realize an inexpensive THz room temperature detector. Preliminary results for THz radiation show that glow discharge indicator lamps as room temperature detectors yield good responsivity and NEP. Development of a Focal Plane Array (FPA) using such devices as detectors is advantageous since the costs of glow discharge detector is around $0.2-$0.5 per lamp, and the FPA images will be diffraction limited. The detection mechanism of the glow discharge detector was found to be enhanced diffusion current which causes decrease of glow discharge detector bias current when exposed to THz radiation.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A Parametric Texture Model Based on Joint Statistics of Complex Wavelet Coefficients

Abstract: We present a universal statistical model for texture images in the context of an overcomplete complex wavelet transform. The model is parameterized by a set of statistics computed on pairs of coefficients corresponding to basis functions at adjacent spatial locations, orientations, and scales. We develop an efficient algorithm for synthesizing random images subject to these constraints, by iteratively projecting onto the set of images satisfying each constraint, and we use this to test the perceptual validity of the model. In particular, we demonstrate the necessity of subgroups of the parameter set by showing examples of texture synthesis that fail when those parameters are removed from the set. We also demonstrate the power of our model by successfully synthesizing examples drawn from a diverse collection of artificial and natural textures.

Optical coherence tomography - principles and applications

Abstract: There have been three basic approaches to optical tomography since the early 1980s: diffraction tomography, diffuse optical tomography and optical coherence tomography (OCT). Optical techniques are of particular importance in the medical field, because these techniques promise to be safe and cheap and, in addition, offer a therapeutic potential. Advances in OCT technology have made it possible to apply OCT in a wide variety of applications but medical applications are still dominating. Specific advantages of OCT are its high depth and transversal resolution, the fact, that its depth resolution is decoupled from transverse resolution, high probing depth in scattering media, contact-free and non-invasive operation, and the possibility to create various function dependent image contrasting methods. This report presents the principles of OCT and the state of important OCT applications. OCT synthesises cross-sectional images from a series of laterally adjacent depth-scans. At present OCT is used in three different fields of optical imaging, in macroscopic imaging of structures which can be seen by the naked eye or using weak magnifications, in microscopic imaging using magnifications up to the classical limit of microscopic resolution and in endoscopic imaging, using low and medium magnification. First, OCT techniques, like the reflectometry technique and the dual beam technique were based on time-domain low coherence interferometry depth-scans. Later, Fourier-domain techniques have been developed and led to new imaging schemes. Recently developed parallel OCT schemes eliminate the need for lateral scanning and, therefore, dramatically increase the imaging rate. These schemes use CCD cameras and CMOS detector arrays as photodetectors. Video-rate three-dimensional OCT pictures have been obtained. Modifying interference microscopy techniques has led to high-resolution optical coherence microscopy that achieved sub-micrometre resolution. This report is concluded with a short presentation of important OCT applications. Ophthalmology is, due to the transparent ocular structures, still the main field of OCT application. The first commercial instrument too has been introduced for ophthalmic diagnostics (Carl Zeiss Meditec AG). Advances in using near-infrared light, however, opened the path for OCT imaging in strongly scattering tissues. Today, optical in vivo biopsy is one of the most challenging fields of OCT application. High resolution, high penetration depth, and its potential for functional imaging attribute to OCT an optical biopsy quality, which can be used to assess tissue and cell function and morphology in situ. OCT can already clarify the relevant architectural tissue morphology. For many diseases, however, including cancer in its early stages, higher resolution is necessary. New broad-bandwidth light sources, like photonic crystal fibres and superfluorescent fibre sources, and new contrasting techniques, give access to new sample properties and unmatched sensitivity and resolution.

Survey on Free Space Optical Communication: A Communication Theory Perspective

Abstract: Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, infrared (IR), and ultraviolet (UV) bands. In this survey, we focus on outdoor terrestrial OWC links which operate in near IR band. These are widely referred to as free space optical (FSO) communication in the literature. FSO systems are used for high rate communication between two fixed points over distances up to several kilometers. In comparison to radio-frequency (RF) counterparts, FSO links have a very high optical bandwidth available, allowing much higher data rates. They are appealing for a wide range of applications such as metropolitan area network (MAN) extension, local area network (LAN)-to-LAN connectivity, fiber back-up, backhaul for wireless cellular networks, disaster recovery, high definition TV and medical image/video transmission, wireless video surveillance/monitoring, and quantum key distribution among others. Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading and sensitivity to weather conditions. In the last five years or so, there has been a surge of interest in FSO research to address these major technical challenges. Several innovative physical layer concepts, originally introduced in the context of RF systems, such as multiple-input multiple-output communication, cooperative diversity, and adaptive transmission have been recently explored for the design of next generation FSO systems. In this paper, we present an up-to-date survey on FSO communication systems. The first part describes FSO channel models and transmitter/receiver structures. In the second part, we provide details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits. Specific topics include advances in modulation, channel coding, spatial/cooperative diversity techniques, adaptive transmission, and hybrid RF/FSO systems.

Free-space optical communication through atmospheric turbulence channels

Abstract: In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received light signal, impairing link performance. We describe several communication techniques to mitigate turbulence-induced intensity fluctuations, i.e., signal fading. These techniques are applicable in the regime in which the receiver aperture is smaller than the correlation length of fading and the observation interval is shorter than the correlation time of fading. We assume that the receiver has no knowledge of the instantaneous fading state. When the receiver knows only the marginal statistics of the fading, a symbol-by-symbol ML detector can be used to improve detection performance. If the receiver has knowledge of the joint temporal statistics of the fading, maximum-likelihood sequence detection (MLSD) can be employed, yielding a further performance improvement, but at the cost of very high complexity. Spatial diversity reception with multiple receivers can also be used to overcome turbulence-induced fading. We describe the use of ML detection in spatial diversity reception to reduce the diversity gain penalty caused by correlation between the fading at different receivers.