Photonics Spectra - March 2009

The night-vision goggles, which can be
mounted on the helmets of fixed- or
rotary-wing aircraft pilots, can be
adjusted for each individual.
Distance from the eye,
alignment and tilt can
be adjusted. Courtesy of
Nivisys Industries.

levels provide the system with high resolution for sharper imaging, higher gain, brightness control and low-distortion output optics.

When the helmet mount is flipped up, by a button release, the goggles shut off to preserve power and to prevent the tube damage that would occur if the unit were exposed to bright light.

Basic vision specifications include a 40° field of view, a focus range set at 25 cm to infinity, a 1 magnification, an optical lens diopter range of 2 to 6 and full-field eye relief of 25 mm. According to Stephens, there is no distance rating for night-vision goggles because atmospheric conditions such as clouds or dust may reduce visibility.

An advantage to the system is that the goggles can be configured to the pilot’s face. Because interpupillary distance can be adjusted from 52 to 72 mm, the eyepieces can be centered directly in front of both eyes. A 27-mm fore-and-aft adjustment of the flip-up base moves the lenses closer to, or farther from, the eyes, and the module also has a 25-mm up-and-down adjustment and minimum tilt angle of 10°, enabling pilots to look beneath the goggles to see the instrument panel. Illumination within the cockpit must be viewed without the goggles, which do not operate at the visible wavelength. The equipment also

can be adjusted for those who wear contacts or glasses.

Stephens said the goggles are made of anodized aluminum, as opposed to plastic, such as those of other ANVIS night-vision goggles, making them lighter in weight at only 514 g. “Pilots bear the weight of the helmet and any radio or communication set that he has to wear on his head,” he said. During aggressive maneuvers, the goggles’ lighter weight will help to lessen any additional g force stresses that a pilot may have to endure, given the heavy strain already on the head and neck.

Differences between the NVAG- 6 and standard ANVIS equipment are that the battery pack is low-profile – it is ear-mounted and protrudes only half as far from the back of the helmet, although it is slightly wider than on standard models; the curved housing conforms to the back of the helmet, eliminating any obstruction or interference with equipment inside the aircraft; and the rear-mounted battery is connected to a cable that extends over the top of the helmet.

The dual-battery power module, which takes regular AA batteries, has a lifetime of more than 40 h; with the reserve pack, the user has a total of more than 80 h of operation.