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.

Automatic target recognition during sensor motion and vibration

Abstract: The resolution capability of imaging systems is affected by blur resulting from vibration and motion during the exposure. This blur is often more severe than electronic and optical resolution limitations inherent in the system. Such image quality degradation must be considered when dealing with the development and analysis of automatic target recognition (ATR) systems. This research analyzes the influence of image vibrations and motion on the probability of acquiring a target with an ATR system. The analysis includes accepted metrics that characterize the relationship existing between the target and its background. A high level of correlation is expected between these factors and the probability of target detection permitting efficient performance in the prediction and evaluation of any ATR system. Such correlations are considered here in the presence of sensor motion and vibration and situations are considered in which the probability of recognition is improved by the motion, despite the blur. The results of this research can be implemented in military applications as well as in developing image restoration procedures for image-blur conditions.

Effects of ionizing radiation on glow discharge detectors

Abstract: Glow discharge detectors in the abnormal glow mode can be used as sensitive detectors of microwave and millimeter wave radiation even in the presence of very intense γ ionizing radiation fields where semiconductor devices cannot operate. In the subnormal glow mode, glow discharge detectors give promise of being able to monitor ionizing radiation fields so intense that the usual electronic detectors saturate.

Motion-blurred image restoration using modified inverse all-pole filters

Abstract: The restoration of vibration-blurred images using mea- sured motion function is considered. Since the blurring filter is of the finite impulse response type, the inverse one is of the all-pole infinite impulse response type. Direct application of the inverse filter to re- store images blurred by vibration is attractive because of reduced computation requirements. Space domain filtering allows high par- allelization of the process and reduction of required processor speed. However, a pure inverse filter provides excessive noise am- plification and is possibly unstable. The proposed technique is to construct a modified inverse filter with preserved all-pole structure and optimized noise and stability properties. A mathematical con- cept was developed using z-transform properties. An experiment testing the proposed technique was setup and the results indicate restoration is 60%-80% of that possible with ideal Wiener filtering. However, the reduced computation and high parallelization can fa- cilitate real-time restoration. © 2004 SPIE and IS&T.

Identification of the blur extent from motion-blurred images

Abstract: In imaging systems in moving vehicles such as tanks, planes, ships, rpvs, etc., resolution is usually limited by motion blur. Successful restoration of blurred images depends primarily on the knowledge we have about the degradation process parameters, i.e., the point spread function (PSF) of the blur and the noise statistics. For many blur situations, such as those deriving from uniform or sinusoidal motion, the most important parameter for proper identification of the PSF is the blur extent parameter. This parameter is the smear size in the blurred image of a point object in the original image. A new method for identification of the blur extent in an image, blurred by motion of the camera during the exposure time, is presented in this paper. The blur extent identification is determined from the motion-blurred and noisy image itself. The identification method developed here is based on a concept that there exists a correlation between the pixels along the blur of the original unblurred pixels. In order to expose the hidden information about the blur extent, the blurred image is first transformed to a secondary image that is more informative about the blur extent, and then the blur extent is extracted from this image using correlation attributes in the image. This permits fast high resolution restoration when the blur extent can complete our knowledge about the blur properties.

Bandwidth maximization for satellite laser communication

Abstract: Free space optical communication between satellites networked together can make possible high speed communication between different places on earth. The basic free space optical communication network includes at least two satellites. In order to communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. The pointing systems for laser satellite communication suffer during tracking from vibration due to electronic noise, background radiation from interstellar objects such as sun, moon, earth and stars in the tracking field of view, and mechanical impact from satellite internal and external sources. Due to vibrations the receiver receives less power. This effect limits the system bandwidth for given bit error rate. In this research we derive an algorithm to maximize the communication system bandwidth using the transmitter telescope gain as a free variable based on the vibration statistics model and the system parameters. Our model makes it possible to adapt the bandwidth and transmitter gain to change of vibration amplitude. We also present an example of a practical satellite network which includes a direct detection receiver with an optical amplifier. A bandwidth improvement of three orders of magnitude is achieved in this example for certain conditions, as compared to an unoptimized system.

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.