HOW NIGHT VISION WORKS

GENERAL OVERVIEW:

How Night Vision Works Video by ITT Click on the image to your right to watch the new "How Night Vision Works Video producted by ITT Industries. Night Vision technology consists of two major types: image intensification (light amplification) and thermal imaging (infrared). Most consumer night vision products are light amplifying devices. Light amplification technology takes the small amount of light, such as moonlight or starlight, that is in the surrounding area, and converts the light energy (scientists call it photons), into electrical energy (electrons). These electrons pass through a thin disk that's about the size of a quarter and contains over 10 million channels. As the electrons travel through and strike the walls of the channels, thousands more electrons are released. These multiplied electrons then bounce off of a phosphor screen which converts the electrons back into photons and lets you see an impressive nighttime view even when it's really dark.

All image intensified night vision products on the market today have one thing in common: they produce a green output image. Like the one your see to your right - >>. But that's where the similarities end.

In the night vision world there are generations that reflect the level of technology used. The higher the generation, the more sophisticated the night vision technology.

Generation 0 - The earliest (1950's) night vision products were based on image coversion, rather than intensification. They required a source of invisible infrared (IR) light mounted on or near the device to illuminate the target area.

Generation 1 - The "starlight scopes" of the 1960's (Vietnam Era) have three image intensifier tubes connected in a series. These systems are larger and heavier than Gen 2 and Gen 3. The Gen 1 image is clear at the center but may be distorted around the edges. (Low-cost Gen 1 imports are often mislabeled as a higher generation.

Generation 2 - The microchannel plate (MCP) electron multiplier prompted Gen 2 development in the 1970s. The "gain" provided by the MCP eliminated the need for back-to-back tubes - thereby improving size and image quality. The MCP enabled development of hand held and helmet mounted goggles.

Generation 3 - Two major advancements characterized development of Gen 3 in the late 1970s and early 1980s: the gallium arsenide (GaAs) photocathode and the ion-barrier film on the MCP. The GaAs photocathode enabled detection of objects at greater distances under much darker conditions. The ion-barrier film increased the operational life of the tube from 2000 hours (Gen 2) to 10,000 (Gen 3), as demonstrated by actual testing and not extrapolation.

When discussing night vision technology, you also may hear the term "Omnibus" or "OMNI". The U.S. Army procures night vision devices through multi-year/multi-product contracts referred to as "Omnibus" - abbreviated as "OMNI". For each successive OMNI contract, ITT has provided Gen 3 devices with increasingly higher performance. ( See range detection chart directly below) Therefore, Gen 3 devices may be further defined as OMNI 3, 4, 5, etc. Current Omnibus contract as of 2006 is OMNI 7.

If you're using night vision to find a lost person in the woods, to locate boats or buoys on the water, or to stargaze into the wilderness, you need Generation 3 because it creates the best images when there is very little ambient light. Generation 2 may be the choice in situations with higher levels of ambient light.

KEY GENERATION DEVELOPMENTS:

  • GENERATION 1 (Developed in 1960's);
    • Vacuum Tube Technology
    • Full Moon Operation
    • Amplification: 1,000
    • Operating Life: 2,000 Hours

  • GENERATION 2 (Developed in 1970's);
    • First Microchannel Plate (MCP) Application
    • One-Quarter Moon Operation
    • Amplification: 20,000
    • Operating Life: 2,500 Hours

  • GENERATION 2+ (1970s)
    • Development increased image tube bias voltage to improve gain.
    • Additionally, a glass faceplate was added to improve resolution.

  • GENERATION 3 (Developed in 1990's);
    • Improved MCP & Photocathode
    • Starlight Operation
    • Amplification: 40,000
    • Operating Life: 10,000 Hour

  • GENERATION 3 Enhanced (2000's);
    • Improvements in the photocathode and MCP resulted in increased gain and resolution.


Expected Operating Life (in hours)

Beyond outperforming all previous technologies, corresponding improvements in reliability have been equally dramatic. GEN III intensifiers have a useful operating life of 10,000+ hours, making tube replacement virtually unnecessary. The intensifier tube normally represents 75% of the overall system cost.

Performance Attributes

There are three important attributes for judging performance. They are: sensitivity, signal-to-noise, and resolution. As the customer, you need to know about these three characteristics to determine the performance level of a night vision system.
Sensitivity, or photoresponse, is the image tube's ability to detect available light. It is usually measured in "µA/lm," or microamperes per lumen. That's why many of our products do not come with standard IR illuminators. With many applications illuminators aren't necessary. Some manufacturers put IR illuminators on their products in order to get acceptable performance under low light conditions.


Signal-to-noise plays a key role in night vision performance. A microchannel plate used to transfer a signal from input to output. Just as high-end stereo equipment gives you quality sound.


Resolution is the third major consideration when purchasing night vision. This is the ability to resolve detail in your image. Some manufacturers put magnified optics in their systems to give the illusion that they have high resolving systems. In the trade-off, field of view is sacrificed. Some models give the option of higher magnification so you can have it if you want it, not because your system needs it to function effectively. Most of Morovision's products offer a uniquely formulated phosphor to create the highest contrasting images, therefore generating the highest resolution products available to the consumer.

Distance and Magnification Charts:

Night Vision Range Chart

*Chart based on night vision system with 1x lens. Recognition range will increase when greater magnification is used.


Characteristics of Night Vision

Using intensified night vision is different from using regular binoculars and/or your own eyes. Below are some of the aspects of night vision that you should be aware of when you are using an image intensified night vision system.

Textures, Light and Dark
Objects that appear light during the day but have a dull surface may appear darker, through the night vision unit, than objects that are dark during the day but have a highly reflective surface. For example, a shiney dark colored jacket may appear brighter than a light colored jacket with a dull surface.

Depth Perception
Night vision does not present normal depth perception.

Fog and Rain
Night vision is very responsive to reflective ambient light; therefore, the light reflecting off of fog or heavy rain causes much more light to go toward the night vision unit and may degrade its performance.

Honeycomb*
This is a faint hexagonal pattern which is the result of the manufacturing process.

Black Spots*
A few black spots throughout the image area are also inherent characteristics of all night vision technology. These spots will remain constant and should not increase in size or number. See example below of an image with black spots.
Photocathode Spots
* Do not be concerned if you see this feature-it is an inherent characteristic found in light amplification night vision systems that incorporate a microchannel plate in the intensifer.