Mission impossible: You're planning a tricky nighttime rescue. Your squad will have to traverse a dark forest, scale the walls of a floodlit compound and enter a building through the basement door. Once inside, the team will have to navigate silently through three pitch-black floors to find the room where armed captors are holding hostages. Kitting out your team with night-vision goggles (NVGs) makes sense, but you're concerned they'll have to keep taking them off and putting them back on as they move from dark to light to dark, with each visor flip leaving them vulnerable to attack. What do you do?

Today, you can buy a better mousetrap. After almost a decade and a half of development by engineers at The O'Gara Group's Sensor Systems Division (formerly STS; Beavercreek, Ohio), the first nonblocking night-vision goggles, which let the wearer see the real and night-vision worlds simultaneously, are on the market. The headgear also allows other information--such as maps, thermal data or incoming instructions--to be viewed via the display.

The new configuration is said to eliminate tunnel vision and vertigo on the wearer's part. The goggles also enhance maneuverability: They don't protrude as far from the face as their predecessors, so their center of gravity is located closer to the user's head, and they feel lighter.

Among the first groups to sign up for the goggles have been the U.K. Special Forces; GSG9, the counterterrorism unit of the German Federal police; and special weapons and tactics (SWAT) teams from several U.S. police forces.

Lower profile for maneuverability
Craig Douglas, SWAT team commander for the Jackson City, Miss., Sheriff's Department, said the goggles' lower profile on the face was a crucial factor in his deciding to procure them for his team. SWAT team officers often must operate in confined spaces--such as behind the wheel--where the bulkiness of conventional NVGs is a problem, Douglas said. Handling weapons is also much easier with the new goggles, he said.

Douglas said his team is currently experimenting with switching between the night-vision mode and information mode, using data from thermal-imaging cameras. Operators of illicit methamphetamine labs--frequent targets of the SWAT team's operations--often have their own night-vision capability, said Douglas, so being able to see in a different spectrum could give his team an edge.

Traditional night-vision goggles essentially look like binoculars, and they have not changed in geometry since the Vietnam War. The displays operate by having a photocathode block the end of the two binocular tubes to absorb incoming light and turn it into electrons. The electrons are then multiplied (using a microchannel plate) and converted back into photons via a fluorescent screen, which is viewed directly by the viewer's eyepiece. There have been several generations of changes to improve the sensitivity and adaptability of the devices, but otherwise, today's NVGs are very similar to those from the 1960s.

Though the simplicity of this straight optical path has many advantages for the engineer, it is not as ideal for users: They have to choose whether they want to see the night-vision view or the real world, because conventional NVGs block out all other sources of light. In addition, the goggles fail in bright conditions: First the images "bloom," or get large and fuzzy, and then a white-out occurs. For pilots, who operate under relatively predictable lighting conditions, this is not necessarily an issue. But for special operations, where an operative may be moving quickly through both lit and unlit areas, it can be a serious problem. On top of that, the cumbersome profile of traditional goggles puts strain on the wearer's neck.