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U.S. Army Soldier & Biological Chemical Command
U.S. Army Soldier Systems Center-Natick
Public Affairs Office
Kansas Street
Natick, MA 01760-5012

Contact: Chief, Public Affairs Office
(508) 233-5340
amssb-opa@natick.army.mil

Date: July 11, 2001
No: 01-42

Program works to protect eye damage from lasers

Natick, Mass. --- Lasers bring precision to the battlefield. They are used in range finders for howitzers, tanks and mortars. They serve as target designators for military munitions. Under the right conditions, they can also damage a soldier's eyesight.

The Laser Eye Protection Program at the U.S. Army Soldier Systems Center (Natick) is dedicated to finding better ways to guard against the danger.

"At the moment we're looking to protect against lasers used on the battlefield," said Barry DeCristofano, a chemical engineer and one of four employees at the Laser Lab. "It's a safety issue as opposed to a survivability issue. They aren't fielded for use as weapons against soldiers."

Lasers were first demonstrated in 1960. Natick then established a laser laboratory to research the field, and Army scientists publicized the danger of flash blindness caused by lasers.

The first laser eye protection was available in 1990 during Operation Desert Storm, according to DeCristofano. Sun, Wind and Dust goggles for combat vehicle troops; Ballistic/Laser Protective spectacles for dismounted prescription eyeglass wearers; and Special Protective Eyewear, Cylindrical System for dismounted troops with normal vision all protect against two or three wavelengths within the electromagnetic spectrum and are fielded items.

"With different lenses, you can block out a few selected wavelengths that are prevalent," he said. "Polycarbonate is used for ballistic protection. Laser protection is an easy add-on and fairly inexpensive."

Certain colors of the visible and near-infrared spectrums are blocked by applying specially-colored dyes to the lenses of protective eyewear similar to those used in sunglasses. However, adding more layers compromises their usefulness.

"When you block all three wavelengths, you can't use it at night," DeCristofano said. "We'd like to protect throughout the visible and near-infrared spectrums, but it's a tall order because you still have to see through it. Right now (the eyewear) would be opaque."

A project to develop laser eye protection into combat vehicle periscopes may remove the need for operators to wear goggles inside. Natick is finishing a three-year joint Science and Technology Objective with the Tank Automotive Research, Development and Engineering Center (TARDEC) in Michigan demonstrating a retrofitted periscope with laser protection.

"It's passive protection. To get the focal planes and still provide a field of view is a big challenge for TARDEC," he said.

Protection with a few colors is now manageable, but the future of battlefield lasers will probably broaden with multiple wavelength frequencies and be tunable like a radio station.

Researchers are seeking ways to block all types of laser wavelengths but only when they're present. DeCristofano compared the idea to sunglasses that darken when they are worn outside on sunny days except that the transition will tune out the frequency in picoseconds (a millionth of a millionth of a second).

He said the best materials the military has aren't sensitive enough to either darken or block the wavelengths. Prototype goggles created in the 1980s with millimeter-sized lenses to help achieve an "instant-on" protection were heavy, bulky, and had a restricted and distorted field of view making them impractical.

Using more sensitive materials and shrinking the optics may be a solution.

In subsequent years, micro-lens manufacturing technology has improved dramatically and is found in common items, such as compact disc players and fax machines.

"We're looking at commercial off-the-shelf items to see if the existing lenses are good enough to use," said DeCristofano. "If they work, they'd be twice as thick as eyewear that the Army now uses."

The Army's Laser Lab at Natick has close ties with laser protection research in the Navy and Air Force because the underlying protection required is common to all.

As technology unfolds, researchers may investigate combining different types of active protection either scattering or absorbing the laser energy. Nanotechnology could be another avenue to remove the laser threat.

Beyond eyes, sensors that someday may feed information to a soldier through a helmet shield display could burn out from laser exposure, which is another project that should keep the Laser Lab looking for solutions.

Lab focuses on eyes
In the days when the nuclear arms race was in full swing, the Laser Lab measured thermal transfer through laboratory materials and clothing systems using a special laser and instrumented manikin.

The data was fed into a computer code that calculates skin burn severity similar to what would happen during an atomic bomb explosion. Two manikins dressed in burned-out desert and woodland camouflage uniforms are reminders of that era.

"We stopped that testing in 1995 as the nuclear threat diminished," said Barry DeCristofano, a chemical engineer at the Laser Lab. "Now we're working solely on eye protection."

Four kinds of lasers in the lab can produce all wavelengths necessary to test laser eye protection. A picosecond-pulse laser is used for probing optical properties of developmental materials, and a nanosecond-pulse laser is used for optical limiting measurements.

Besides lasers, the lab uses equipment to test other requirements. Ballistic evaluation of eye armor is obtained through an air gun that shoots fragments at speeds meeting military and civilian specifications. Eyewear is placed on a manikin head inside a steel container to catch fragments striking the glasses.

The lab's spectrophotometer measures how much light travels through material at each wavelength. "It's used to match dyes and to see if fielded eyewear still passes the specs," DeCristofano said.

Accelerated measurements are conducted on solar exposure and temperature extremes with a weatherometer and computer-controlled environmental chamber. Industry benefits from the facilities as well. Eyewear manufacturers have used the facilities in testing agreements to provide accelerated exposure and see if the products still meet all specifications, he said.

Natick is part of the U.S. Army Soldier and Biological Chemical Command (SBCCOM). For more information about SBCCOM or the Soldier Systems Center (Natick), please visit our website http://www.sbccom.army.mil.

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