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.

Medical image restoration of dynamic lungs using optical transfer function of lung motion

Abstract: When carrying out medical imaging based on detection of isotopic radiation levels of internal organs such as lungs or heart, distortions and blur arise as a result of the organ motion during breathing and blood supply. Consequently, the image quality declines, despite the use of expensive high resolution devices. Hence, such devices are not exploited fully. There is a need to overcome the problem in alternative ways. Such as alternative is image restoration. We suggested and developed a method for calculating numerically the optical transfer function (OTF) for any type of image motion. The purpose of this reserach is restoration of original isotope images (of the lungs) by reconstruction methods that depend on the OTF of the real time relative motion between the object and the imaging system. This research uses different algorithms for the reconstruction of an image, according to the OTF of the lung motion, which is in several directions simultaneously. One way of handling the 3D movement is to decompose the image into several portions, to restore each portion according to its motion characteristics, and then to combine all the image portions back into a single image. As additional complication is that the image was recorded at different angles. The application of this reserach is in medical systems requiring high resolution imaging. The main advantage of this approach is its low cost versus conventional approaches.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Restoration of motion-blurred images

Abstract: This paper deals with the problem of restoration of images blurred by relative motion between the camera and the object of interest. This problem is common when the imaging system is in moving vehicles or held by human hands, and in root vision. For correct restoration of the degraded image it is useful to know the point spread function (PSF) of the blurring system. In this paper we propose a straightforward method to restore motion blurred images given only the blurred image itself. The method first identifies the PSF of the blur, and then use it to restore the blurred image. The blur identification here is based on the concept that image characteristics along the direction of motion are effected mostly by the blur and are different from the characteristics in other directions. By filtering the blurred image we emphasize are presented for both synthetic and real motion blur.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Statistical models for the desert aerosol size distributions and comparison to MODTRAN models

Abstract: Predictions of atmospheric transmittance in desert aerosol environments using MODTRAN code diverge significantly from measured data. Good prediction of the desert particulate size distribution is required in order to predict atmospheric scattering and absorption parameters. It is also essential to the prediction of the aerosol atmospheric modulation transfer function which is often the dominant component of the overall atmospheric MTF. Recently, an effort to predict statistics but not size distribution according to simple weather parameters has been made for coarse desert aerosols. A quantitative analysis of the desert particulate size distribution models was also performed. In this research the size distribution parameters measured by optical counters are related to weather parameters. Known statistical and analytical models such as MODTRAN relate the size distribution parameters only to relative humidity for continental atmospheres. Although humidity has a significant role in the prediction of aerosol size statistics, other weather parameters are seen here to strongly influence also the size distribution parameters. Comparisons such as the above can be used to predict under which conditions the MODTRAN aerosol models have good or poor accuracy. It is also hoped that they will lead to improvements in MODTRAN, improving the accuracy of the humidity dependence as well as by incorporating other meteorological parameters into the MODTRAN prediction models.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Non-Optogalvanic Signal Characteristic Times in Prebreakdown Discharges

Abstract: The prebreakdown regime, which exists in a gas cell during the time interval of free charge density growth from first electron-ion pair generation until the onset of breakdown, is characterized by low bias and incident field intensities In our experiment, dc biased Ne and Ar gas cells at 90 torr each were illuminated with laser pulses Both the incident laser field and dc bias field were smaller, sometimes much smaller, than those required for gas breakdown by each alone Under these conditions, clear-cut electrical signals of amplitude on the order of tens of millivolts are observed as a response to laser pulse irradiation at wavelengths non resonant to any gas atomic transitions We called these non-breakdown responses “prebreakdown or precursor signals” In 1,2 such prebreakdown signal magnitude, polarity and occurrence probability as a function of incident field intensities were discussed

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.