Lynn Savage, email@example.com
ARLINGTON, Va. – US Air Force scientists have devised a way
to make un-manned aerial vehicles (UAVs) better eyes in the sky, besides making
them lighter and more efficient.
Also known as drones or pilotless aircraft, UAVs increasingly
are being used for reconnaissance missions by both military and commercial operators.
The aircraft can acquire intelligence on enemy combatants, locate terrorism suspects,
measure instances of extreme weather, and inspect remote oil, gas and power lines,
among many other uses.
In remote sensing and imaging operations, however, UAVs must peer
through varying atmospheric conditions, most of which degrade the results. Adaptive
optics systems, which are known chiefly for improving celestial images acquired
by ground-based telescopes that also are subject to atmospheric distortions, would
help, except that they are too bulky and heavy for practical use aboard UAVs.
Adaptive optics systems work by discerning errors in the wavefronts
of light that reflects off imaging targets. Aside from the optics, which include
a deformable mirror that uses tiny actuators to correct wavefront errors before
the light is passed on to a CCD, these systems require a high-power computer to
operate at high speeds. A significant portion of the weight and volume of an adaptive
optics system belongs to the computer.
Dr. Geoff Andersen of the US Air Force’s Laser and Optics
Research Center in Colorado Springs, Colo., and his colleague, Dr. Kent Miller of
the Air Force Office of Scientific Research in Arlington, tackled the problem by
stripping out the computer. To perform the intensive calculations required, they
replaced the computer with a holographic wavefront sensor technology upon which
is recorded the individual responses of each actuator on the deformable mirror.
Using a holographic adaptive optics system permits computer-free operation of unmanned aerial
vehicles for surveillance missions. Courtesy of the US Air Force Office of Scientific Research.
When the hologram containing the actuator response functions
used during imaging, wavefront errors are measured as intensity outputs
array of fast photodetectors, then sent directly to the mirror’s
This makes the system an all-optical closed loop that requires no
“Adding the holographic wavefront sensor technology improves
speed and functionality while also decreasing mass, volume and complexity,”
Andersen said. “By removing the computer, we can make the entire system smaller
and lightweight and over 100 times faster.”
The system, dubbed HALOS (Holographic Adaptive Laser Optics System),
has been tested as a proof of concept. According to Andersen, he and Miller are
now in the process of testing full autonomous operation of the technology. They
will also be trying it with more sensitive detectors.
“The idea of incorporating adaptive optics into UAV surveillance
systems is now a real possibility,” he said. “This is not possible with