Throughout the history of warfare, nighttime engagements had been dramatically reduced due to the need for proper illumination. Bright light sources on the battlefield were obviously problematic in that tactical positions and activity could be seen by both sides! Finally, in the 1950's, new technologies for allowing soldiers to fight at night, as well as in the daytime, were beginning to appear and are constantly being improved upon today.
Night Vision Devices (NVD's) allow the user to see and maneuver with little to no existing light. These devices have the capability to magnify the most minute amount of ambient light many thousands of times (usually 2000-5000 times or more) through the use of their main component – and image intensifier. The NVD is an electro-mechanical device that intensifies any existing light from the stars, moon and even distant glow in the sky from far away city lights. After the image is magnified, it is visible on the phosphor display of the NVD.
Why is it green? The phosphor display is intentionally colored green because the human eye can differentiate more shades of green, which makes it the most visible color in the spectrum. Today, manufacturers such as ATN, have even been able to remove the green tint from the phosphor display after studies that showed nighttime scenes appeared more natural in black & white, known as WPT (White Phosphorous Technology) and the information appeared clearer and sharper in some instances. Some NVD users even complained that the green color made them dizzy or nauseous at the white phosphorous option may help to eliminate that as well.
The distance at which a human-sized figure can be recognized through an NVD is based on the weather conditions, magnification of the objective lens plus the strength and quality of the image intensifier tube. Typically, the average viewing range for night vision is from about 100 to about 400 feet. What many night vision users don't realize is that even the best devices will not provide the same level of clarity and sharpness you would get during the daytime.
Since those very early days, night vision has evolved into several Generations of improved product performance. For simplicity, we will limit this article to Generations I through III and their variants. The early Generation I devices typically magnified ambient light by roughly 1000X and the intensifer tube had a life expectancy of about 2000 hours. Generation II tubes last for about 2500-4000 hours and amplify light about 20,000 times. And finally, Generation III tubes can last for 10,000 hours and amplify as much as 30,000-50,000 times! So, roughly 50% of the cost of any NVD is in the image intensifer tube, and the later generations will undoubtedly be more costly, but will produce brighter, sharper images.