To improve the resolution and field of view of high-energy Compton-scattered x-ray and gamma-ray imaging systems,
we have developed and tested apodized imaging optics based on apertures with depth-dependent cross sections
fabricated in an x-ray-absorbing material. Through ray-tracing modeling, we determined the optimum aperture shapes
(apodizations) that maximize the field of view and/or resolution of the system. Such apodized apertures can be used
either in single-aperture optics, or in coded-aperture arrays. Potential applications of this technology include
nondestructive evaluation (NDE) of materials and structures, in particular Compton imaging tomography (CIT), x-ray
and gamma-ray astronomy, and medical imaging.
In this paper we describe a new nondestructive evaluation (NDE) technique called Compton Imaging Tomography (CIT)
for reconstructing the complete three-dimensional internal structure of an object, based on the registration of multiple
two-dimensional Compton-scattered x-ray images of the object. CIT provides high resolution and sensitivity with
virtually any material, including lightweight structures and organics, which normally pose problems in conventional
x-ray computed tomography because of low contrast. The CIT technique requires only one-sided access to the object,
has no limitation on the object's size, and can be applied to high-resolution real-time in situ NDE of large
aircraft/spacecraft structures and components. Theoretical and experimental results will be presented.
Binary sensor systems are various types of analog sensors (optical, MEMS, X-ray, gamma-ray, acoustic, electronic, etc.),
based on the binary decision process. Typical examples of such "binary sensors" are X-ray luggage inspection systems,
product quality control systems, automatic target recognition systems, numerous medical diagnostic systems, and many
others. In all these systems, the binary decision process provides only two mutually exclusive responses: "signal" and
"noise." There are also two types of key parameters that characterize either system (such as false positive and false
negative), or a priori external-to-system conditions (such as absolute probabilities). In this paper, by using a strong
medical analogy, we analyze a third type of key parameter that combines both system-like and a priori information, in
the form of so called Bayesian Figures of Merit, and we show that the latter parameter, in the best way, characterizes a
binary sensor system.
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.
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.
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
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.
Fiber Bragg gratings are used in a wide variety of devices including sensors, tunable filters, and signal controllers for Wavelength Division Multiplexing. Bragg gratings can be formed in an optical fiber by illuminating the fiber from the side with a pattern of ultraviolet light. Most gratings are made using 240-nm light. However, by using 330-nm light the grating can be written right through the standard polymer coating of the fiber, which preserves the fiber's mechanical strength. We discuss some of the mechanisms that degrade the strength of fiber gratings. We also discuss applications of mechanically strong fiber gratings, including very wide (> 50 nm) tunable filters.
1D photonic crystals offer extraordinarily low group velocities and high dispersion near their bandgaps. They therefore have an immediate application in CDMA and optical encoding. In our approach we have chosen photonic crystal implementations using long fiber optic Bragg gratings. This system has been numerically investigated and modeled for experimentally realizable structures. We have developed an experimental technique to measure the group delay, produced by 1D Photonic Bandgap structures, in the time domain. At the core of this technique we used a tunable optical pulse source. It consisted of a 1.55 micrometers , 160 fs mode-locked fiber laser with a bandwidth of 50 nm. One nm spectral slices were taken from this laser to obtain picosecond pulses that were tunable. The group delay was measured using a commercial autocorrelator as an ultrafast optical detector and cross-correlator. This technique allowed us to measure the effective dispersion incurred by optical pulses propagating through the grating. A maximum group delay of 10 ps was measured for a 3mm fiber Bragg grating. We have experimentally demonstrated the sensitivity of the group delay as a function of wavelength in the vicinity of the grating bandgap. Our experimental results were quantitatively confirmed by both theoretical and simulation predictions. We also performed experimental studies on cascaded fiber gratings and showed that group delay was additive for the two gratings measured. The use of 1D photonic crystals for pulse shaping and coding applications is important because of its inherent flexibility. By going to the other side of the photonic bandgap it is possible to make conjugate gratings, reversing the dispersion,and performing the task of decoding. Transmission losses and dispersion compensation in this spread spectrum approach will also be presented.