Night Vision Goggles (NVG) During the history of warfare, operations at night have always been degraded significantly, if not totally avoided. Typically, soldiers fighting at night have had to resort to artificial illumination, e.g., at first fire and later with light sources such as searchlights. The use of light sources on the battlefield had the detrimental result of giving away tactical positions and information about maneuvers. The advent of new technologies initially in the 1950's and continuing into the present time has changed this situation. The engineers and scientists at the US Army's Communications-Electronics Command (CECOM) Night Vision & Electronic Sensors Directorate (NVESD) have discovered ways to capture available electro-magnetic radiation outside that portion of the spectrum visible to the human eye and have developed equipment to enable the American soldier to fight as well at night as during the day and to "Own the Night". Night vision devices (NVDs) provide night fighters with the ability to see, maneuver and shoot at night or during periods of reduced visibility. The Army used two different types of NVDs - image intensifiers and thermals. Image-Intensifying Devices are based upon light amplification and must have some light available. These devices can amplify the available light from 2,000 to 5,000 times. Thermal Forward-Looking Infrared (FLIR) detectors - sometimes called "sensors" - work by sensing the temperature difference between an object and its environment. FLIR systems are installed on certain combat vehicles and helicopters. NVGs are electro-optical devices that intensify (or amplify) existing light instead of relying on a light source of their own. Image intensifiers capture ambient light and amplify it thousands of times by electronic means to display the battlefield to a soldier via a phosphor display such as night vision goggles. This ambient light comes from the stars, moon or sky glow from distant manmade sources, such as cities. The devices are sensitive to a broad spectrum of light, from visible to infrared (invisible). Users do not look through NVGs, you look at the the amplified electronic image on a phosphor screen. Light enters the NVG through an objective lens and strikes a photo cathode powered by a high energy charge from the power supply. The energy charge accelerates across a vacuum inside the intensifier and strikes a phosphor screen (like a TV screen) where the image is focused. The eyepiece magnifies the image. An NVG phosphor screen is purposefully colored green because the human eye can differentiate more shades of green than other phosphor colors. Like cameras, NVGs have various image magnifications. The distance at which a human-sized figure can be clearly recognized under normal conditions (moon and star light, with no haze or fog) depends on both the magnifying power of the objective lens and the strength of the image intensifier. The maximum viewing range is 100 feet to 400 feet. A soldier can conduct his combat missions without any active illumination sources using only image intensifiers. The main advantages of image intensifiers as night vision devices are their small size, light weight, low power requirements and low cost. These attributes have enabled image intensifier goggles for head-worn, individual soldier applications and resulted in hundreds of thousands of night vision goggles to be procured by the US Army. Research and development continues today on image intensifiers in the areas of longer wavelength spectral response, higher sensitivity, larger fields of view and increased resolution. The view through NVDs can be a lot like looking down a tunnel. Your normal field of view is almost 190 degrees - but that is cut down to 40 degrees with NVDs. That side -- or "peripheral" -- vision you're accustomed to, and from which you often see dangers, is just not there. To adjust for that you must constantly turn your head to scan for the dangers on either side of you that you can't see in your narrow field of view. (See the article in this issue titled, Proper Scanning Critical to NVG Operations). At their best, NVGs cannot provide the same level of sharpness to what you see as what you're accustomed to in the daytime. While normal vision is 20/20, NVGs can, at best, provide only 20/25 to 20/40, and even this is possible only during optimal illumination and when you have a high-contrast target or scene. As either illumination or contrast decreases, the NVG's visual acuity drops, giving you an even more "fuzzy" image. Normally you use both eyes (binocular vision) to pick up cues to help estimate the distance and depth of an abject. However, with NVDs you are essentially using one eye (monocular) vision, which can pose real problems. For example, when you are wearing NVDs and you view two objects of different sizes that are side-by-side, the larger object appears to be nearer. When you view overlapping objects through an NVD, the one that is in f...