In this paper a new approach to 3D Compton imaging is presented, based on a kind of <i>finite element</i> (FE) analysis. A
window for X-ray incoherent scattering (or Compton scattering) attenuation coefficients is identified for breast cancer
diagnosis, for hard X-ray photon energy of 100-300 keV. The point-by-point power/energy budget is computed, based on a
2D array of X-ray pencil beams, scanned vertically. The acceptable medical doses are also computed. The proposed <i>finite
element tomography</i> (FET) can be an alternative to X-ray mammography, tomography, and tomosynthesis. In experiments,
100 keV (on average) X-ray photons are applied, and a new type of pencil beam collimation, based on a Lobster-Eye Lens
(LEL), is proposed.
High-resolution, wide-field-of-view hard X-ray telescopes are essential for detecting and studying cosmic sources in the
10-100 keV photon energy band, which are typically inaccessible to conventional Wolter I X-ray telescopes. To focus
such high-energy photons, we developed special Lobster-Eye optics consisting of multiple reflective channels with
square cross sections, which are formed by intersecting two sets of semiconductor-grade gold-coated flat silicon
elements. Reflective channels with square cross sections The presented hard X-ray Lobster-Eye telescope lens designed
for the 10-80 keV energy band consists of approximately 100 channels in both the horizontal and the vertical directions,
with the angle between the adjacent plates being less than 1'. An array of such lenses, in which the orientation of each
lens is independently controlled, can be used as an adaptive X-ray focusing device capable of changing its imaging
properties depending on the user-selected mode. In the wide-angle operation, the individual lenses are aligned toward a
common center to form a lobster-eye lens with a large (~2°) field of view, which would be suitable for monitoring stellar
or galactic X-ray bursts. For observing a specific event, the telescope can be switched to the high-sensitivity mode by
aligning the axes of the individual lenses in parallel so that they are all pointing to the region of interest, effectively
adding up the effective areas of individual lenses (up to ~1600 cm<sup>2</sup> at 40 keV). In the paper we will discuss the system
performance simulations and the experimental results using initial prototype Lobster-Eye lenses.
In this paper, biologically-inspired optical imaging systems, including fish eye, bug eye, lobster eye, and RGB color
vision, are discussed as new lensing systems for military and homeland security applications. This new area of interest
includes UV, VIS, IR, and X-ray part of electromagnetic spectrum. In particular, recent progress at Physical Optics
Corporation will be discussed, including such applications as hyperspectral/multi-spectral imagery, video surveillance,
and X-ray inspection.
Non-invasive real-time detection and identification of high explosives and improvised explosive devices, illicit materials
hidden inside suitcases, vehicles, containers or behind metal and non-metal walls become critically important for safety
and security worldwide. In this paper we will discuss non-scanning, portable real-time detection X-ray backscattering
system based on novel Lobster-Eye X-ray focusing optics, which focuses backscatter photons from fully obscured objects
several meters away that are being irradiated by short high-power X-ray pulses. Due to the ability of Lobster-Eye lenses to
focus X-rays, such imaging systems collect more photons into a smaller spot, compared to traditional pinhole systems. This
results in a higher signal-to-noise ratio and better spatial resolution. The signal-to-noise ratio can be further improved by
using pulsed X-ray irradiation and a gated X-ray camera. The images can be further improved by software processing,
which allows to reconstruct the object with high accuracy adequate for detection with high probability and low false alarm
This paper discusses a new approach to X-ray non-intrusive (NDE) inspection based on hard X-ray imaging optics. A
new X-ray lens, called lobster-eye-lens (LEL) is the transmission lens, based on reflection optics, with grazing-angle
deflection of 0.2° and photon energy of 40-100 keV. The lens reflection-optics is based on large, high-quality X-ray
mirrors with r.m.s. lower than 1 nm. The through-the-wall inspection capability of such a system, based on Compton
back-scattering, can be applied for longer ranges, (up to 100 m in the air), and thick walls (over 2 cm for wood, and over
2 mm for metal). CONOPS examples are given for homeland security applications.
Detecting and identifying organic and metallic targets at distances from 50 m to 100 m is difficult for hard X-ray
detection devices, especially when targets (such as improvised explosive devices (IEDs)) are concealed behind metal
(steel) and non-metal (plastic, wood, rocks, soil, etc.) walls. At least two problems are inherent to detection at such
long distances: (1) the air attenuation of X-rays, which can be significant for standoff distances of x = 50 m (100 m
total for 2x); and (2) a scattering factor proportional to x<sup>4</sup> that comes from the divergence of X-rays propagating
from a source to a target and X-rays backscattering from a target (usually, Compton backscattering in low Z-number
materials). The compensation of these factors by novel lobster-eye hard X-ray optics is analyzed in this paper. The
analysis and the optimization of the hard X-ray lobster eye lens for realistic parameters are also discussed.
We propose a new imaging device for the long infrared spectral range, inspired by the natural eye of a lobster. Such
a lobster-eye lens is composed of reflecting channels with a square cross section capable of wide angle of view and
practically omni-directional imaging. As in large-aperture lenses, aberrations can significantly degrade the image.
We show two methods of reducing aberrations: by selecting proper material for the mirrors and by making channels
with absorbing sections.
The angular distribution of the inelastic scattering of photons at low energies (≤80 KeV) has been measured in organic material, soil, rocks, wood, steel sheet, and water. The measurements have been performed under air inside an X-ray shield cabinet using X-rays tube as a photon source and a thermoelectrically cooled CdTe detector. Measurements have been taken for both single and combined materials. The contributions of inelastic scattering of photons for the lower Z material in a given configuration have been extracted. The measured signal is primarily Compton scattering. The measured inelastic scattering contributions were compared with the calculated inelastic scattering cross sections according to the Klein-Nishina theory, updated to include a practical energy distribution of an X-ray tube beam. Relatively good agreement was found for all targets under investigation. The slight discrepancy is attributed to photoelectric effect and sample configuration. Present results may act as a guide for optimization of X-ray imaging sensors and in particular of those based on lobster eye X-ray optics suitable for cargo inspection, improvised explosives detection, non-destructive evaluation, and medical imaging.
In this paper, we discuss hard x-ray optics, in general, and lobster-eye focusing optics, in particular, for concealed object
detection, at longer distances. The longer distance (~50m) scenario is important for Improvised Explosives Detection
(IED), "seeing through walls," "seeing objects under ground," and related applications.
A new approach to hard X-ray imaging is proposed, based on staring optics consisting of a lobster-eye lens. This new Staring Imaging Lobster-Eye X-Ray approach is especially suited to X-ray lobster-eye imaging of non-astronomical objects at finite distances, because the staring optics replacing the standard scanning optics, result in an extremely efficient power budget, making possible not only the use of low-efficiency Compton backscattering but also operation with low-flux X-ray beams, increasing operator safety. The lobster-eye optics, consisting of square-cross-section microchannels, transmit an X-ray beam by total external reflection. This mode of operation has already been verified for viewing astronomical objects. Its major challenge is minimizing image defocusing by apodization. For this purpose, a new lens imaging equation is derived, and a new local optical axis concept is defined. Applications include medical imaging, cargo inspection, non-destructive testing, industrial and security safeguards, and surveillance.
The present work describes the modeling and the simulation of a concept of novel sensor-single tube color image intensifier intended for direct observation of the night side of the Earth or other planets in the visible range of the spectrum from orbit, or as airborne sensor or as color image preamplifiers for color CCD sensors. The color image sensor consists of an objective and microchannel tube which contains an input multielement color filters pattern, matched and registered with output multielement color filters pattern. Input/output color filters patterns, which determine the spatial sampling of the image, were organized both in hexagonal RGB mosaic and in RGB stripes configuration. The present work is aimed at describing the basic theoretical models for simulation and analysis of the color image sensor including quantification and optimization of its performance. The basic models include the major color intensifier parameters, namely, spectral characteristics of the color filter elements, their size and spacing; spectral characteristics of the photocathode and phosphor; MCP's pore size, center-to-center spacing and gain; voltages and distances of spacing photocathode -- MCP<SUB>in</SUB> and MCP<SUB>out</SUB> -- screen; tolerance of registration of input- output filters, etc. For a number of technologically achievable parameters it is shown that: (1) the resolution of the device, based on the Nyquist frequency for hexagonal mosaic filter configuration can reach approximately 20 color (line pairs)/mm; for stripe filter configuration it can reach approximately 30 color (line pairs)/mm along stripes and approximately 10 color (line pairs)/mm across stripes with adequate MTF; (2) the light non-uniformity is less than 5% which is insignificant; (3) realistic set of filters provides a good color transformation -- compatible to the transformation in color CRT displays. The model also describes the color edge transformation. As it was shown, cross-talk level in single basic color element from neighboring elements is about 6%, and its influence is expressed in moving the color coordinates of a uniform color on the tube's output toward the 'white point' on the CIE chromaticity diagram. Modeling showed that color imaging can be achieved at very low light levels with good color resolution and color preservation. The first color images were successfully obtained from a prototype, demonstrating that the proposed concept indeed produces a color vision image intensifier device with good color imaging abilities. The computer simulation agrees well with photometrical and colorimetrical parameters of the first workable prototypes.
Proc. SPIE. 2863, Current Developments in Optical Design and Engineering VI
KEYWORDS: Point spread functions, Optical filters, Microchannel plates, Image resolution, Image filtering, Image intensifiers, Modulation transfer functions, Color vision, Color imaging, RGB color model
The present work delineates the principles of a direct vision color image intensifier tube. An arrangement consisting of microchannel tube in conjunction with input color filters mosaic and matched output color filters mosaic is described. It is shown that color imaging can be achieved at very low light levels with acceptable color resolution. The present work is aimed at describing the basic theoretical model for simulation and analysis of color imaging tubes including quantification and optimization of its performance. The basic model incudes the major color tube components and operating parameters, namely, spectral characteristics of the RGB basic color filter's elements, its diameter and center-to-center spacing; spectral characteristic of the photocathode and phosphor; MCP's pore size, center-to-center spacing and gain; voltages and spacing between electrodes; tolerance of registration of input-output filters, etc. For a number of technologically achievable parameters it is shown that: (1) the resolution of the device, based on the Nyquist frequency, can reach 16 color (line pairs)/mm; (2) the light uniformity is about 5% which is insignificant; (3) realistic set of filters provides a good color transformation -- compatible to the transformation in color CRT displays; (4) cross-talk level in single basic color element from neighboring elements is about 6%; (5) the light amplification is compatible to conventional intensifier tubes; (6) the proposed configuration is not too sensitive to design parameters. It is possible to conclude that realistic configurations can produce a color direct vision image intensifier device with high resolution and good color transformation. The device simulations serve to design a workable prototype.