1. Night vision is the ability to see in low light conditions. Whether by
biological or technological means, night vision is made possible by a
combination of two approaches: sufficient spectral range, and sufficient
intensity range. Humans have poor night vision compared to many
animals, in part because the human eye lacks a tapetum lucidum.[1]
Contents
[hide]
1 Types of ranges
o 1.1 Spectral range
o 1.2 Intensity range
2 Biological night vision
3 Night vision technologies
4 Night vision goggles
5 Active infrared
6 Laser range gated imaging
7 Thermal vision
8 Image intensifier
9 Night vision devices
10 Automotive night vision
11 See also
12 Patents
13 References
14 External links
[edit]Types of ranges
[edit]Spectral range
Night-useful spectral range techniques can sense radiation that is
invisible to a human observer. Human vision is confined to a small
portion of the electromagnetic spectrum called visible light. Enhanced
spectral range allows the viewer to take advantage of non-visible
sources of electromagnetic radiation (such as near-
infrared or ultraviolet radiation). Some animals can see using much more
of the infrared and/or ultraviolet spectrum than humans.

2. [edit]Intensity range
Sufficient intensity range is simply the ability to see with very small
quantities of light.[2]
Many animals have better night vision than humans do, the result of one
or more differences in the morphology and anatomy of their eyes. These
include having a larger eyeball, a larger lens, a larger
optical aperture (the pupils may expand to the physical limit of the
eyelids), more rods than cones (or rods exclusively) in the retina, and
a tapetum lucidum.
Enhanced intensity range is achieved via technological means through
the use of an image intensifier, gain multiplication CCD, or other very
low-noise and high-sensitivity array of photodetectors.
[edit]Biological night vision
For more details on this topic, see Adaptation (eye).
In biological night vision, molecules of rhodopsin in the rods of
the eye undergo a change in shape as they absorb light. Rhodopsin is
the chemical that allows night-vision, and is extremely sensitive to light.
Exposed to a spectrum of light, the pigment immediately bleaches, and it
takes about 30 minutes to regenerate fully, but most of
the adaptation occurs within the first five or ten minutes in the dark.
Rhodopsin in the human rods is less sensitive to the longer
red wavelengths of light, so traditionally many people use red light to
help preserve night vision as it only slowly depletes the eye's rhodopsin
stores in the rods and instead is viewed by the cones. However
the USsubmarine force ceased using red lighting for night adaptation
after studies found little significant advantage of using low level red over
low level white lighting.[3]
Many animals have a tissue layer called the tapetum lucidum in the back
of the eye that reflects light back through the retina, increasing the
amount of light available for it to capture. This is found in
many nocturnal animals and some deep sea animals, and is the cause
of eyeshine. Humans lack a tapetum lucidum.

3. Nocturnal mammals have rods with unique properties that make
enhanced night vision possible. The nuclear pattern of their rods
changes shortly after birth to become inverted. In contrast to
contemporary rods, inverted rods have heterochromatin in the center of
their nuclei andeuchromatin and other transcription factors along the
border. In addition, the outer nuclear layer (ONL) in nocturnal mammals
is thick due to the millions of rods present to process the lower light
intensities of a few photons. Rather than being scattered, the light is
passed to each nucleus individually.[4] In fact, an animal's ability to see in
low light levels may be similar to what humans see when using first- or
perhaps second-generation image intensifiers.[citation needed]
[edit]Night vision technologies
Film about the development of military night vision technology
Night vision technologies can be broadly divided into three main
categories:
Image intensification
Image intensification technologies work on the principle of
magnifying the amount of received photons from various natural
sources such as starlight or moonlight. Examples of such
technologies include night glasses and low light cameras.
Active illumination
Active illumination technologies work on the principle of coupling
imaging intensification technology with an active source of
illumination in the near infrared (NIR) or shortwave infrared (SWIR)
band. Examples of such technologies include low light cameras.
Thermal imaging

4. Thermal imaging technologies work by detecting the temperature
difference between the background and the foreground objects.
Some organisms are able to sense a crude thermal image by means
of special organs that function as bolometers. This allows
thermal infrared sensing in snakes, which functions by detection of
therm
HOW NIGHT VISION WORKS

5. GENERAL OVERVIEW:
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 is less expensive than thermal, however, higher-end and
more effective night vision tubes can become more expensive. 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 mislabeGeneration 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)

6. to 10,000 (Gen 3), as demonstrated by actual testing and not extrapolation.
Generation 4 - Myth vs. Fact
Some say that generation (Gen) 4 is the most advanced night vision you can buy. This is not the
case. To dispel this myth, let's start with the basics. There are four Generations of night vision;
however, they are Gen 0-3, not Gen 1-4. Historically, the U.S. Army has defined each Generation
of night vision. In the late 90's the Army did define Gen 4 as the removal of the ion barrier film
creating a "filmless" tube. This new advancement was to reduce halos while increasing sensitivity,
signal-to-noise ratio (SNR) and resolution, for overall improved performance. While performance
was improved, the lack of an ion barrier in Gen 4 tubes led to high failure rates, ultimately
leading the U.S. Army to recant the existence of Gen 4 definition. Recognizing the high failure
rates of Gen 4 tubes, ITT chose to improve upon the existing Gen 3 technology and create a
"thin-filmed" tube. By keeping the protective ion barrier, but greatly reducing its thickness, ITT
was able to maintain the reliability of Gen 3 while—at the same time—delivering on the Army's
performance requirements intended for Gen 4. This innovation resulted in the production of the
Gen 3 thin-filmed tube, which is now the highest performing Gen 3 tube available. Not long after,
the gated power supply was added and the PINNACLE® tube was born. The Generation 3
PINNACLE® tube is the most advanced night vision manufactured to date.
led as a higher generation.