NIGHT VISION TECHNOLOGY
( NIGHT VISION DEVICE )
WHAT WE WILL COVER!
What is night vision
Night vision approaches
Working of night vision technology
Night vision Devices
Ability to see in dark environment
Whether by biological or technological means, night vision
is possible by combination of two approaches: sufficient
spectral range, and sufficient intensity range
Human have poor night vision compared to many animals
because the human eye does not have tapetum lucidum
Tapetum lucidum is a layer of tissue in the eye of many
animals which improves vision in low night condition.
Night Vision Approaches!!
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
Sufficient intensity range is simply the ability to
see with very small quantities of light.
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.
Working of night vision devices!!
Night vision technologies can be broadly divided into two main categories:
Image intensification technologies work on the principle of
magnifying the amount of received photons from various natural
sources such as starlight or moonlight.
Thermal imaging technologies work by detecting the temperature
difference between the background and the foreground
1)IMAGE INTENSIFICATION !!!!
This method of night vision amplifies the available light
to achieve better vision. An objective lens focuses
available light (photons) on the photocathode of an
image intensifier. The light energy causes electrons to be
released from the cathode which are accelerated by an
electric field to increase their speed (energy level). These
electrons enter holes in a micro channel plate and bounce
off the internal specially-coated walls which generate
more electrons as the electrons bounce through.
Night vision goggles are electro-optical
devices that intensify existing light
instead of relying on a light source.
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, hence why it becomes green.
Green is a good choice for two reasons.
One is that the phosphors, the things that
glow and make the colour are relatively
easy to make it green. And because the
eye is more sensitive to green light than
virtually any other wavelength, it means
that you can make your display dimmer
than any other wavelength and your eye
will be sensitive to it.
WORKING OF THERMAL IMAGING!!!
Infrared thermography, thermal imaging, and thermal video are examples
of infrared imaging science.
Thermal imaging cameras detect radiation in the infrared range of the
electromagnetic spectrum (roughly 9000–14,000 nanometers or 9–14
µm) and produce images of that radiation, called thermo grams. Since
infrared radiation is emitted by all objects above absolute zero according
to the black body radiation law, thermography makes it possible to see
one's environment with or without visible illumination.
When viewed through a thermal imaging camera, warm objects stand out
well against cooler backgrounds; humans and other warm-blooded
animals become easily visible against the environment, day or night. As a
result, thermography is particularly useful to military and other users of
Night Vision Devices!!!
A night vision device (NVD) is an
optical instrument that allows
images to be produced in levels of
light approaching total darkness.
They are most often used by the
military and law enforcement
agencies, but are available to civilian
The term usually refers to a
complete unit, including an image
intensifier tube, a protective and
generally water-resistant housing,
and some type of mounting system.
1) Night glasses
Night glasses are
telescopes or binoculars
with a large diameter
objective. Large lenses can
gather and concentrate
light, thus intensifying light
with purely optical means
and enabling the user to see
better in the dark than with
the naked eye alone
2) Thermal vision
Thermal imaging cameras
are excellent tools for night
vision. They detect thermal
radiation and do not need a
source of illumination.
They produce an image in
the darkest of nights and
can see through light fog,
rain and smoke.
3) Image intensifier
The image intensifier is a vacuum-tube based device
that converts visible light from an image so that a
dimly lit scene can be viewed by a camera or the
naked eye. While many believe the light is
"amplified," it is not.
At that time infra-red was commonly called black light, a
term later restricted to Ultraviolet. It was not a success due to
its size and cost. They were active devices, using a large
infrared light source to illuminate targets. Their image
intensifier tubes function using an anode and an S-1
photocathode, made primarily of silver, cesium, and oxygen
and a electrostatic inversion with electron acceleration were
used to achieve gain.
Generation 1 (GEN I)
First generation passive devices, introduced during
the Vietnam War, were an adaptation of earlier
active GEN 0 technology, and rely on ambient light
instead of an infrared light source. Using an S-20
photocathode, their image intensifiers produce a
light amplification of around 1,000×, but are quite
bulky and require moonlight to function properly.
AN/PVS-2 Starlight scope
Generation 2 (GEN II)
Second generation devices feature an improved image-
intensifier tube utilizing micro-channel plate (MCP) with an
S-25 photocathode, resulting in a much brighter image,
especially around the edges of the lens. This leads to
increased illumination in low ambient light environments,
such as moonless nights. Light amplification is around
20,000×. Also improved were image resolution and
Generation 3 (GEN III)
Third generation night vision systems maintain the MCP from Gen II, but
now use a photocathode made with gallium arsenide, which further
improves image resolution. In addition, the MCP is coated with an ion
barrier film for increased tube life. The light amplification is also
improved to around 30,000–50,000×.Power consumption is higher than
GEN II tubes.
Omnibus-VII (GEN III+)
GEN-III OMNI-VII devices can differ from standard Generation 3 in two
important ways. First, an automatic gated power supply system regulates
the photocathode voltage, allowing the NVD to instantaneously adapt to
changing light conditions. The second is a removed or greatly thinned ion
barrier. The disadvantage to a thin or removed ion barrier is the overall
decrease in tube life from a theoretical 20,000 hrs mean time to failure
(MTTF) for Gen III type, to 15,000 hrs MTTF for GEN IV type.
However, this is largely negated by the low number of image intensifier
tubes that reach 15,000 hrs of operation before replacement.
Common applications for night vision include: