Human eyeballs are the oldest sensor used by pilots, and they’re increasingly at risk from lasers.
To counter the harmful effects of directed energy, the Vision Science Lab at the Naval Medical Research Unit Dayton is looking at ways to protect eyeballs from low-intensity lasers, while still allowing pilots to see clearly enough to fly. This evaluation is done at the behest of the Coast Guard’s Office of Aviation Forces, which wants a way to mitigate the threat handheld lasers post to safety and search and rescue missions.
Lasers, even and especially hand-held laser-pointers, are bright enough and powerful enough to interfere with eyeballs, even ones at altitudes far above the person waving the pointer. The FAA has guidelines for how people should responsibly use lasers outdoors, and where they should keep them pointed (down, away from planes or other aircraft).
“Handheld lasers can produce levels of solar radiant energy that exceed the maximum FAA exposure recommendations. Non-lethal continuous wave (CW) laser exposures can produce veiling glare, obscuring a significant portion of an aircraft windscreen while reliably reducing speed and accuracy of responses to aviation-relevant visual tasks during critical phases of flight,” write Dr. Michael Reddix and Lt. Cmdr. Micah Kinney, the researchers leading this project. “These factors are also capable of producing visual impairments such as temporary scotoma or a temporary disturbance in vision.”
The work was done in partnership with the U.S. Air Force Research Laboratory, specifically the branch that works on photonic materials. The goal was to develop low-cost laser eye protection glasses, to mitigate the flight safety risk lasers pose to planes and rotary-wing craft.
“In short, there is no good and complete defense against the wide variety of laser wavelengths and powers out there,” says Phil Broughton, certified laser safety officer. “That said it isn't hopeless, as there's only so many good deployable lasers for the field.”
To meet those threats, there are to go-to options: glasses with reflective coatings or plastic with absorptive dyes. But reflective coatings have three drawbacks: the coating is easy to scratch and useless one scratched, which is a hard sell for a military use. They are also heavy, since they need to be on glass, and the reflective coating is only useful for a narrow band of wavelengths, a range a few nanometers wide. Within that, and unscratched, the reflective coating is incredible, but unless it’s fielded against a specific laser with a known frequency, it’s unlikely to be the most effective option here.
“Absorptive are dye based, tinting plastic. Plastic is light & comfortable, you can form them in any shape you like for eyewear. The dyes can be broad spectrum but not necessarily great. Their real problem is that they always tend to work at half of the wavelengths you need," says Boughton, “So, if there’s a 1064nm beam, it’s only half the optical density you need to block the other beam that’s at 532nm. Also, depending on how the laser is operating, the dyes can saturate and stop working.”
There is also the not-insignificant matter that absorptive glasses, in blocking a range of laser wavelength, also block a significant amount of the visible spectrum, which replaces temporary vision obscurity for permanently decreased vision. Not super great when flying a plane.
One way future planes plan to mitigate the risk to pilot eyeballs is to feed information through cameras on the plane into a heads-up display on the pilot’s helmet, but that’s still a future solution, and doesn’t address the needs of pilots encountering lasers now.
Whatever method Reddix and Kinney picked for their solution, they recommended that the new laser-mitigating goggles receive flight acceptance training in the next few months. If the Coast Guard’s experience with the goggles is successful, it’s possible the other services could adopt them for protection, too. Which means the next time Airmen fly near the gulf of Aden, it may be safe to check out Djibouti without risking temporary blindness.