Transcript NIGHTVISION TECHNOLOGY SUBMITTED BY Srabani Kanungo 0301223362 (ENTC) INTRODUCTION  Night vision technology enables you to see objects clearly at night at distances up to several hundred.

NIGHTVISION
TECHNOLOGY
SUBMITTED BY
Srabani Kanungo
0301223362 (ENTC)
INTRODUCTION
 Night vision technology enables you to see
objects clearly at night at distances up to several
hundred yards in the absence of any artificial
light. People, buildings, vehicles & details of the
landscape viewed through a modern night vision
system appear almost as if illuminated while the
same objects viewed with a naked eye would
appear only as indistinct shadow .Depending
upon the way it is implemented it is broadly
classified into two types
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(i) Biological Night vision (ii)Technical Night
vision
TYPES OF NIGHTVISION
 Depending upon the way it is implemented it
is broadly classified into two types
 Biological Night vision
 Technical Night vision
BIOLOGICAL NIGHT VISION
 In biological night vision, molecules of rhodopsin in the rods
of The eye undergo a change in shape as light is absorbed
by them. The peakrhodopsin build-up time for optimal
night vision in humans is 30 minutes.Rhodopsin in the
human rods is insensitive to the longer red wavelengths of
light, so many people use red light to preserve night
vision as it will not deplete the eye's rhodopsin stores
in the rods and instead is viewed by the cones. Some
animals,such as cats, dogs, and deer, have a structure
called the tapetum inthe back of the eye that reflects light
for even better night vision than humans, in which only
10% of the light that enters the eye falls on photosensitive
parts of the retina.
TECHNICAL NIGHT VISION
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BASIC PRINCIPLE
It based upon the principles of photo electric effect
EQUATIONS:
E=hf , E=W + EK
Where
E=Energy of the radiation
W=Work function
EK=Kinetic energy of the electrons
h=Plank’s constant
f=Frequency of the radiation
RANGES OF NIGHT VISION
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ENHANCED SPECTRAL RANGE
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Enhanced spectral range techniques make the viewer sensitive to types of
light that would be invisible to a humanobserver. Human visionis confined
to a small portion of the electromagnetic spectrum called visible range.
Enhanced spectral range allows the viewer to take advantage of nonvisible sources of electromagnetic radiation (such as near-infrared or UV
radiation)
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ENHANCED INTENSITY RANGE
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Enhanced intensity range is simply the ability to see with very small
quantities of light. Although the human visual system can, in theory, detect
single photons under ideal conditions, the neurological noise filters limit
sensitivity to a few tens of photons, even in ideal condition. Some
animals have evolved better night vision through the use of a larger optical
aperture, improved retina composition that can detect weaker light over a
larger spectral range, more photo efficient optics in the eye, and improved
neurological filtering which is more tolerant of noise. 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 photo detectors.
IMAGE ENHANCEMENT TECHNIQUE
 Image-enhancement technology is what
most people think of when you talk about
night vision. In fact, image-enhancement
systems are normally called night-vision
devices (NVDs). NVDs rely on a special tube,
called an image-intensifier tube, to collect
and amplify infrared and visible light.
 The image-intensifier tube changes
photons to electrons and back again.
how image enhancement works:
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A conventional lens, called the objective lens, captures ambient light
and some near-infrared light.
 The gathered light is sent to the image-intensifier tube. In most NVDs,
the power supply for the image-intensifier tube receives power from
two N-Cell or two "AA" batteries. The tube outputs a high voltage, about
5,000 volts, to the image-tube components.
 The image-intensifier tube has a photocathode, which is used to
convert the photons of light energy into electrons.
 As the electrons pass through the tube, similar electrons are released
from atoms in the tube, multiplying the original number of electrons by
a factor of thousands through the use of a micro channel plate (MCP) in
the tube. An MCP is a tiny glass disc that has millions of microscopic
holes (micro channels) in it, made using fiber-optic technology. The MCP
is contained in a vacuum and has metal electrodes on either side of the
disc. Each channel is about 45 times longer than it is wide, and it works
as an electron multiplier.
 At the end of the image-intensifier tube, the electrons hit a
screen coated with phosphors. These electrons maintain
their position in relation to the channel they passed
through, which provides a perfect image since the electrons
stay in the same alignment as the original photons. The
energy of the electrons causes the phosphors to reach an
excited state and release photons. These phosphors create
the green image on the screen that has come to
characterize night vision.
 The green phosphor image is viewed through another lens,
called the ocular lens, which allows you to magnify and
focus the image. The NVD may be connected to an
electronic display, such as a
 monitor, or the image may be viewed directly through the
ocular lens.
DIFFERENT GENERATIONS OF
INTENSIFIER TUBE
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Generation 0
Generation 0 devices took a lot of power to use, for both the tube and
the IR illuminator, had a very distorted picture due to a cone-shaped
electrode design, and a short tube life due to the high electrical voltage.
Generation 0 featured a photocathode made of a mixture of silver,
caesium, and oxygen called S-1 which provided approximately 60 mA/lm
sensitivity to light.
 Generation 1
 Generation 1 devices are also called "Starlight scopes", and were a
tremendous improvement upon generation 0. They are much more
power efficient, amplify light better, and produced a superior image.
Generation 1 also used a different photocathode, S-20, which provided
about three times the photo sensitivity of Generation 0.
 Generation 1 remains one of the most popular types of night vision
today. Despite its poor performance, its low cost entices people who are
looking to pick up night vision as a toy.
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Generation 2
Generation 2 was a major technological breakthrough. Although the
photocathode material, S-25, wasn't much of an improvement over
Generation 1's S-20, generation 2 devices introduced the microchannel plate
.The microchannel plate consists of a bundle of thousands of tiny glass fibres
fused together in parallel, sliced transversely, and polished on both faces.
Electrons impinging on one side of the plate tend to travel along the fibres,
perpendicular to the plate's faces, thus preserving a coherent image. As
good as Generation 2 was, though, it was soon to be overshadowed by a
new photocathode material.
Generation 3
Generation 3 is the latest "generation" and is in use by the U.S. military and
others. It is essentially generation 2 technology with a new photocathode
material—gallium arsenide and a better MCP. Gallium arsenide provides far
better response to near-infrared light. This is very important as the majority
of starlight is in the IR spectrum. However, this comes at a cost of decreased
sensitivity to blue light.
 Later Generations
 There are newer night vision systems available.
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Generation 3 Ultra and Generation 4 tubes exist.
Most civilian equipment remains based on
Generation 3 equipment and lower, however.
Generation 3 Ultra and 4 still use MCP technology,
but are designed to offer greater range, and higher
resolution.
1. 2. . 3.
It is quite easy to see everything during the day...
...but at night, you can see very little.
3. View through Night vision devices.
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IR VISION
This is another way of achiveing night vision by using thermal imaging.
BASIC PRINCIPLE
It based on the two principle.
(i)PLANK’S BLACKBODY RADIATION
Every object above zero degree kelvin radiates electromagnetic
energy.
 (ii)WIEN’S DISPLACEMENT LAW
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Wave length of the radiation decreases as temperature increases and
vice versa.
 They are simple devices that do not produce a net amplification of light,
but rather allow a user to see near-infrared light. Along with beam
filters, this allowed snipers to illuminate their target without their target
being aware of it.
THERMAL IMAGING
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(i)A special lens focuses the infrared light emitted by all of the objects in
view.
(ii)The focused light is scanned by a phased array of infrared-detector
elements. The detector elements create a very detailed temperature
pattern called a thermogram. It only takes about one-thirtieth of a
second for the detector array to obtain the temperature information to
make the thermogram. This information is obtained from several
thousand points in the field of view of the detector array
(iii)The thermogram created by the detector elements is translated into
electric impulses.
(iv)The impulses are sent to a signal-processing unit, a circuit board with
a dedicated chip that translates the information from the elements into
data for the display.
(V)The signal-processing unit sends the information to the display,
where it appears as various colors depending on the intensity of the
infrared emission. The combination of all the impulses from all of the
elements creates the image.
TYPES OF IR DEVICES
 UNCOOLED -Most common device, operate
in room temperature detector is made of InSb.It has a built in battery
 CRYOGENICALY COOLED -Most expensive ,
made of In-Ga-As ,liquid nitrogen is used to
cool the system below 00c .its working range
is from -200c to 20000c
APPLICATION
 ELECTRICAL INTERFACES
 In the electrical distribution station,one portion of it is hot due to
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short circuit or some problem. But it will not visible to the naked
eye.
SECURITY SYSTEM
This another application of IR imaging. The radiation pattern of
every human beingis unique. So by taking this pattern we can
store it in some database & can use for future reference.
TO DETECT THE FLAW IN ELECTRONICS CHIP
Due to some defect in the circuit the portion of this circuit is
more hot As compare to the other portion of the circuit which will
not visible to the naked eye. But by scan it with the help of a
IR device we can detect the flaw. Its one of the popular
application of IR imaging.
APPLICATION
 MECHANICAL APPLICATION
 Its used in the steel industry to monitor the blast furnace. We can
detect the hot portion of the furnace and take necessary
precaution.
 CIVIL APPLICATION
 There is always a difference of temperature between outside
environment & the innerside of the building. If there is any crack
then there will be a temperature flow within the crack. Hence this
part of the building is more hot as compare to the other & hence
radiate more. In otherwords the wet portion ,which is portion of
crack will radiate more & we can take necessary precaution .
 The similar kind of incident happened during the Bhopal gas
tragedy. In the above image there is a fracture which is not visible
to the ordinary Eye
CONCLUSION
Night vision is one of the emerging
technology which is used in Different fields
like in industry, by the military persons. So
more Sophisticated technology needs to
be developed to implement night vision in
a better way.