DESCRIPTION: LEP and sensor protection currently used by the Air Force incorporates cutting-edge technologies (absorptive dyes and/or reflective technologies) to protect against lasers at a variety of wavelengths in the infrared (IR) and visible portions of the electromagnetic (EM) spectrum.  Dyes tend to be broadband absorbers–their absorption at wavelengths other than the desired wavelength(s) frequently reduces overall visible luminous transmittance (VLT) to levels that are not compatible for night use.  Also, dyes tend to decompose at the temperature of molten polycarbonate and can be bleached by solar exposure and exposure to high irradiance levels.  These effects complicate the need to achieve a desired level of laser protection, and dye decomposition products can produce unacceptable optical effects.  Dyes can (in principle) be imbibed or coated onto eyewear after it is molded, but the VLT problem remains.

Reflective technologies (dielectric coatings and holograms) are applied after molding and can be made with sharp cutoffs around the wavelength(s) of interest, providing much higher VLT than dyes.  However, only a select few functional reflective coatings have been placed on large or highly curved surfaces, and none have been placed on complex shapes.  Further, protection provided by reflective technologies is dependent upon the angle of incidence of the incoming light.  Narrow protective notches and high incident angles can cause the wavelength against which protection is desired to become uncovered by blue shifting at high angles.

For a highly curved or complex-shaped sensor or seeker optical train or visor, some of the light coming in from any direction will always be at a high incidence angle.  So even if reflective technologies could be put onto large, complex surfaces, their usefulness is by no means certain.  Because reflective technologies can be complex and time consuming to manufacture, the resulting eyewear or optical elements often very expensive to produce.  Finally, because they reflect light, these technologies have been found to produce distracting (and sometimes obscuring) nuisance reflections in the visual field, so visual compatibility of the laser protection with the avionics display on the inside surface of a visor can be problematic.

This topic will focus on the design, fabrication, and validation of a solution that for seeker/sensor and LEP technologies not currently in use.  The resulting visor/eyeware/optics will provide a minimum optical density (OD) of 4 (OD6 desired) in the near IR (700 to 1550 nm) but be transparent to visible light between 400 and 700 nm and free from internal reflections.  Ideally, the LEP technology solution will create a passive barrier that protects against both continuous wave (CW) and pulsed laser threats, will be compatible with incorporation into a large platform polycarbonate visor.

The LEP solution performance should not be angularly dependent.  The technology must be compatible with, and must not degrade the ballistic protection properties of, polycarbonate and other commercial optical polymer substrates and not be hygroscopic for long term submersion or high humidity environment degradation.

The proposed technology must provide high VLT (minimum of 70 percent-greater than 80 percent desired) and be color neutral in the visible range.  This technology must also be compatible with new narrow band dye technology.  In terms of optical quality, it is paramount that negative factors such as haze, distortion, aberration, prism, and artifacts are minimized so as not to impair visual performance or create distractions in the visual field.

The proposed solution should be compatible with military sensor/seeker/aircraft environments and be process application suitable for current military optical components in a manufacturing environment.  It desired that the proposed solution also provide a high level of rejection for both laser threats and high powered microwave emissions as well.
 

PHASE I: Perform a technology feasibility assessment, and deliver a model of the conceptual solution, develop optical data and proof-of-principle devices to support the feasibility of the proposed solution, and a Phase II technology development plan. Show path to 80 percent broadband transmittance from visible and laser/high powered microwave protection greater than OD4, with OD6 desired.
 

PHASE II: Demonstrate the proposed solution by delivering seeker, sensor, eyewear and visor solutions incorporating the proposed technology with supporting performance data. Demonstrate in actual prototypes with on and off axis illumination against threats.  Show performance over wide range of military environmental conditions and the manufacturability compatible with current military sensor/seeker/eyewear manufacturing processes.  Provide a manufacturing transition plan/readiness assessment.
 

PHASE III DUAL USE APPLICATIONS: Air Force, Army and Navy have requirements for LEP for personnel. Potentially any field that uses lasers or laser eye protection-commercial aviation, medical/dental laser surgery, lab technicians, welding, manufacturing, laser research, consumer eye protection).  Demonstrate the manufacturability.
 

REFERENCES:

1. “Beam Weapons Revolution,” Jane’s International Defense Review, pp. 34 - 41, August 2000.1C.
 

2. Sheehy, James B. and Morway, Phyllis E., “Laser-protective technologies and their impact on low-light level visual performance,” Laser-Inflicted Eye Injuries: Epidemiology, Prevention, and Treatment, SPIE Proceedings, Vol. 2674, pp. 208 - 218, Stuck, Bruce E. and Belkin, Michael, Eds. (1996).
 

3. Visor performance specification, MIL-V-4351.
 

4. Physical and optical evaluation of reflective dielectric laser eye protection (LEP) spectacles, Human Effectiveness Directorate, Directed Energy Bioeffects Division’ Optical Radiation Branch, 8111 18TH Street, Brooks AFB, Texas 78235-5215, September, 2001.
 

5. ANSI Standard Z136.1. American national standard for the safe use of lasers, American National Standards Institute, Inc., New York, 2000.
 

6. ANSI Standard Z87.1 American national standard for occupational and education eye and face protection, American National Standards Institute, Inc., New York, 1993.