Newsletters: 2004, Issue 1

PSI's Technologies Assist with Homeland Security

Homeland security is now receiving the attention and resources appropriate to a national priority. New technologies and systems for the detection, prevention and mitigation of terrorist attacks are needed, and organizations such as the Homeland Security Advanced Research Projects Agency have been established to develop and deploy them.

Instrumentation pod with aerodynamic skins removed showing AIRIS (upper right), an IR camera for tracking (lower left) and intensified visible camera for tracking (lower right)

Physical Sciences Inc. has been involved in research programs affecting homeland security for some time, and this newsletter summarizes several successful projects. PSI has developed passive infrared imagers for chemical and biological detection that have now reached the pre-production stage. Operating in the 8 to 11 micron spectral region, we have demonstrated the capability to detect and identify chemical vapor plumes at a range of several kilometers. The Adaptive InfraRed Imaging Spectroradiometer (AIRIS) will enable wide area surveillance of gaseous, aerosol, and liquid threats. We also expect to find commercial applications in both industrial and medical markets.

In the coming months and years, we envision the insertion of our sensors into distributed sensor networks for a variety of military and civilian applications. Innovative network architectures for urban environments are under development, and PSI is committed to making key contributions to the deployment of practical systems.

THz Technologies for Chemical and Biological Screening

PSI is applying TeraHertz (THz) wavelength sensors to portal security and screening. THz frequencies occupy the gap between traditional long-wave IR and mm-wave portions of the electromagnetic spectrum. Sensors operating at these wavelengths possess many interesting properties, including the ability to penetrate common non-metallic containers, packaging and clothing materials. In addition, the THz portion of the spectrum contains characteristic absorption features of organic crystals (such as explosives), biologically significant chemical compounds (such as components of bacteria), and low-energy protein conformational modes.

With support from the Air Force Research Laboratory, PSI is testing concepts for THz Quantum Cascade Laser sensors that will provide the ability to remotely detect hidden explosives at distances up to at least 30 m. This standoff capability will permit security forces to rapidly screen approaching individuals for explosives hidden under clothing while the threat is still at a safe distance. The Naval Surface Warfare Center is supporting a fundamental study aimed at quantifying the THz spectral signatures of biological and chemical agents. The data is being used to design automated portal software that will screen for controlled substances within sealed packages.

A recent effort for the Army Research Office assessed the feasibility of THz sensors for dispersed anthrax detection. New programs are underway that combine time-domain THz spectroscopy with Atomic Force Microscopy to probe features of unlabeled biological materials in their native state. This latter capability could permit direct interrogation of biochemical molecules, protein-expression, and intracellular signaling within living cells.

Underwater Imaging for Port Security

Inspection is a key enabler for security, and there are many surfaces to inspect in the underwater world - ship hulls, piers and pilings, and harbor floors, usually in conditions of poor visibility. Conventional optical imaging cannot handle the turbidity. Sonar does not always provide the required resolution. Laser imaging provides the potential to cut through backscatter to provide high-quality pictures.

The Marine Optics and Imaging group at PSI is collaborating with Harbor Branch Oceanographic Institution (HBOI) of Ft. Pierce, FL, to investigate next-generation underwater laser imaging systems. The laser systems in current use operate only in a “look-down” mode to search for targets on the sea floor. For port security, systems should be capable of imaging horizontal, vertical, or angled surfaces. And while conventional systems image reflected light at a single wavelength, it is desirable to operate at multiple wavelengths to enhance signal-to-noise ratio, or to image fluorescence to improve recognition of biological growth. PSI and HBOI are investigating alternatives for next-generation system design, with the goal of creating smaller, more versatile systems compatible with a variety of deployment platforms, including remotely operated and autonomous vehicles.

Handheld Laser Technology for Pipeline Protection

The U.S. natural gas transmission and distribution system comprises over 1,000,000 miles of pipeline, 1,700 transmission stations and 17,000 compressors, serving approximately 61,000,000 customer meters. Maintaining the security and integrity of this system is a continual process of searching for, locating, and repairing leaks. Leak surveying is very labor intensive, in part because all currently available natural gas detectors must be positioned within a leak plume to detect the leak. PSI, in collaboration with Heath Consultants and the Northeast Gas Association, and with additional funding from PSE&G, SoCal Gas, and the U.S. EPA and DoE, has developed a laser-based methane detector that provides stand-off detection of leaks with detection capabilities comparable to commonly-used flame ionization detectors. The Remote Methane Leak Detector (RMLD) is based on the established measurement technology known as tunable diode laser absorption spectroscopy.

The RMLD system includes a handheld optical transceiver and a shoulder-mounted controller. The transceiver transmits an eyesafe laser beam onto any topographic surface at up to a 100 ft. distance, and collects some of the laser light reflected by that surface. The controller processes the received light signal to detect the amount of methane in the laser''s path. The entire system weighs approximately 6 lbs., including rechargeable batteries that power the device for more than 8 hours.

Field tests of prototype RMLD units have been ongoing by several gas distribution companies since March 2003 with excellent results. Design of production units is currently underway and market introduction is planned for late this year.

Without entering dog-protected yard, surveyor employs RMLD to inspect a gas meter for leaks

Microscale Retro-reflector Taggant Technology

Research Support Instruments (RSI), a wholly-owned subsidiary of PSI, in collaboration with the Applied Physics group of Princeton University, has produced 250-micron micro-machined corner cube retro-reflectors utilizing microelectro-mechanical systems (MEMS) fabrication techniques. Funded by a Small Business Technology Transfer grant monitored by the Office of Naval Research, the microscale retro-reflectors were developed for application as a passive optical personnel tag. An array of retro-reflectors was produced photolithographically and surface-coated with a simple thin film optical filter to prevent retro-reflection of visible light. Once freed from the fabrication substrate, the microscale retros can be applied to targets.

Array of 250-micron wide, gold-coated retro-reflectors

Retro-reflectors are optical systems which return light back to a source with low angular divergence. The most familiar applications of retro-reflecting materials are highway safety markers and range finding targets. RSI's microscale hollow corner cube retro-reflector technology offers several advantages to the microsphere retro-reflectors used in other systems, including insensitivity to index of refraction of the environment, optical quality, and flexibility in the manufacturing process.

Applications of these optically interrogated retro-reflectors include the tagging of enemy or friendly forces, non- combatants, documents, materiel, and vehicles. Commercial markets include law enforcement, hospital security, wildlife management, and currency and document validation.

Near IR Surveillance Illuminator

PSI has developed a novel illuminator that transforms essentially any light source into a highly spatially uniform beam, useful for a number of important applications. The Integrating Projection Optic (IPO), takes full advantage of compact, electrically efficient, near infrared diode lasers to produce wide angle (20 to 60 deg), uniform beams that are invisible to the eye but readily detected with standard silicon based video cameras and advanced night vision goggles. Thus, PSI's illuminator can be used in a number of situations that could be encountered by anti- terrorist personnel. Some of these applications include building and other asset security, covert surveillance, hostage/barricade situations, building search, video/photo surveillance, search and rescue, and hostage rescue.

The system uses patented technology and can be applied to light sources at wavelengths from 200 nm to 2000 nm. PSI has completed extensive testing from 800 to 980 nm in the near IR using high power diode lasers. The wide angle of illumination provided by the IPO is particularly useful for broad area searches and surveillance and is also compatible with visible light sources for more traditional security lighting applications.

Figure shows a darkened scene illuminated with a standard police flashlight. The dark region of the image is typical of these devices.

Figure shows the same scene illluminated with an IPO. The image reveals significantly more detail.

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Physical Sciences Inc.
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