Some people apparently think it's funny to shine laser pointers at aircraft that are taking off or landing. Unfortunately, though, the glare of the laser beams can temporarily blind pilots, potentially leading to crashes. Installed in planes' windshields, new liquid crystal technology could keep that from happening.
Although scientists have previously tried to develop laser-pointer countermeasures for aircraft, they've been challenged by the fact that the pointers can emit beams of different wavelengths – we see those as different laser colors, such as red, green or blue. Most of the systems created so far have only been capable of blocking one wavelength.
Based out of Illinois' Lewis University, a team led by Dr. Jason Keleher set out to improve upon that state of affairs. The researchers started with a solution of liquid crystals, known as N-(4-methoxybenzylidene)-4-butylaniline. It's called MBBA for short.
In lab tests, the solution was placed between two 1-inch (25-mm)-square panes of glass. It started out in a transparent liquid state, but when voltage was applied, the crystals aligned with the electrical field, causing it to temporarily shift to an opaque crystalline state. Once that phase-change had occurred, the MBBA was capable of blocking up to 95 percent of red, green and blue laser light. It was able to do so partly by scattering the light, partly by absorbing the laser energy, and partly through the process of cross-polarization.
Additionally, the change was triggered by the lasers. When an integrated photoresistor detected the laser light, the system automatically applied voltage to the MBBA, turning it opaque. As soon as the laser ceased, the voltage was shut off, and the solution became clear again.
The scientists are now working on scaling their model up to the size of a full aircraft windshield. Plans call for that windshield to integrate an array of individual MBBA panels, so that only the parts of the glass that were directly hit by a laser beam would go opaque. The team will also be trying different types of liquid crystal solutions, which may offer even better performance.
Keleher and colleagues are presenting their research this Monday, at the American Chemical Society Spring 2019 National Meeting and Exposition.
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