CHAPTER 1

INTRODUCTION

Night vision is the ability to see in a dark environment. 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 does not have a tapetum lucidum.

The tapetum lucidum (Latin: "bright tapestry”, plural tapeta lucida) is a layer of tissue in

the eye of many vertebrate animals, that lies immediately behind or sometimes within the retina. It

reflects visible light back through the retina, increasing the light available to the photoreceptors.

This improves vision in low-light conditions, but can cause the perceived image to be blurry from

the interference of the reflected light. The tapetum lucidum contributes to the superior night vision

of' some animals. Many of' these animals are nocturnal especially carnivores that hunt at night, and

their prey. Others are deep sea animals. Although some primates have a tapetum lucidum, humans

do not. The tapetum lucidum enables an animal with it to see in dimmer light than the animal

would otherwise be able to. This is of use to the animal, but it is of use also to humans. Human

uses include scanning for reflected eye shine to detect and identify the species of animals in the

dark, and deploying trained search dogs and search horses at night. Historically, its function was

regarded as simply to increase the light intensity of an image on the retina.

Night vision technology, by definition, literally allows one to see in the dark. Originally

developed for military use, it has provided the United States with a strategic military advantage,

the value of which can be measured in lives. Federal and state agencies now routinely utilize the

technology for site security, surveillance as well as search and rescue. Night vision equipment

has evolved from bulky optical instruments in lightweight goggles through the advancement of

image intensification technology.

Night vision has had many improvements throughout the course of history. Its beginning

date back to Second World War when the Germans idealized a very effective way to easily use

their sniper rifles during the night. This was later researched very deeply into because night

vision proved to have a devastating advantage for those who used it [1].

1

HISTORY

Research into night vision devices began in the 1940s. The United States military

established a night vision technology development program by the late 1940s, and by the 1950s

had come up with viable infrared viewing systems. This was an active technology, meaning it

used a directed beam of infrared light. Though the beam itself was invisible to the unaided eye,

opponents armed with equivalent technology could easily pick up the beam. The infrared viewers

used in the 1950s and 1960s are referred to as "Generation 0" technology.

ITT Corporation (now MIT Industries, Inc.) in Roanoke, Virginia, began producing night

vision devices for the United States military in 1958. The United States Department of Defense

founded its own Night Vision Laboratory in 1965, dedicated to improving the existing

technology. During the 1960s, scientists developed the first workable passive night vision

systems. These devices were called "Starlight" systems because they were able to pick up and

amplify images seen only by starlight. They are also known as "Generation I" devices. They

actually worked best in moonlight. Generation 1 night vision devices were used in combat for the

first time during the Vietnam War.

Improved technology developed shortly after the war led to smaller, less bulky night

vision devices with better resolution. These more reliable instruments were called "Generation

2." The United States military continued to develop and refine night vision technology during the

1970s and 1980s, fitting weapon sights with night vision targeting devices and training pilots in

night vision goggles. Passive Generation 2 devices were able to produce a good visible image in

very low light situations.

"Generation 3" technology was developed in the late 1980s. These new night vision

devices used gallium arsenide for the photo cathode material inside the image intensifier tube.

This produced better resolution even in extremely low light situations. United States forces used

night vision devices extensively in the Persian Gulf War, where the technology allowed troops to

see not only in the dark but through dust and smoke as well. By the late 1990s, the Department

of Defense had reduced its funding for night vision development, and some manufacturers began

searching for consumer markets for the gear. Individuals may buy night vision devices in the

United States, but their export is still restricted [2].

2

ADVANTAGES OF NIGHT VISION DEVICES

The human eye is a very sensitive and versatile image detector but has a number of physical

limitations. An electronic image intensifier can provide a fundamental improvement and

perception gain over the unaided eye by capturing more photons from the scene and using these

more efficiently. More photons are collected by employing an objective lens of larger diameter

than that of the pupil of the dark-adapted eye. The only limitations in this respect are the

practical considerations of size and weight of the instrument depending upon the application. The

co11ected photons can be used more efficiently by detecting them with a higher quantum

efficiency than that of the retina. The most suitable type of detector for this purpose appears to be

a photo emissive cathode consisting of a compound of the alkali metals: sodium, potassium and

cesium. The human eye is a very sensitive and versatile image detector but has a number of

physical limitations. An electronic image intensifier can provide a fundamental improvement and

perception gain over the unaided eye by capturing more photons from the scene and using these

more efficiently. More photons are collected by employing an objective lens of larger diameter

than that of the pupil of the dark-adapted eye. The only limitations in this respect are the

practical considerations of size and weight of the instrument depending upon the application. The

co11ected photons can be used more efficiently by detecting them with a higher quantum

efficiency than that of the retina. The most suitable type of detector for this purpose appears to be

a photo emissive cathode consisting of a compound of the alkali metals: sodium, potassium and

cesium with antimony. Surfaces of this kind have quantum efficiencies of up to about 20% for

white light and can make much more efficient use of the night-sky radiation than the retina. On

the other hand, an increased integration time beyond the 0.2 second of the fully dark adapted eye

is only of limited use in practical applications because it reduces the ability to detect moving

objects which appear to become more as and more blurred. It is thus possible in principle to

obtain considerable improvement in perception over the dark adapted eye by employing an

instrument with a large diameter of its objective lens and inefficient photocathode. However, this

potential perception gain can be achieved in practice only if the detected photons in the form of

emitted photoelectrons produce scintillations on a final viewing screen that are bright enough to

be registered on the observer’s retina. This condition leads to the requirement of a minimum

amount of light amplification or lumen gain in the instrument. Such a lumen gain can be

achieved with the aid of image-intensifier tube. Much research has been done, especially in the

3

fields of electronic image intensifier tubes, as well as optical technology relating to the optical

components of a night vision system (i.e. the objective lens and the magnifying eyepiece)with a

view to making the performance these night vision devices better and better.

1.1 BASICS OF LIGHT

In order to understand night vision, it is important to understand something about light.

The amount of energy in a light wave is related to its wavelength: Shorter wavelengths have

higher energy. Of visible light, violet has the most energy, and red has the least. Just next to the

visible light spectrum is the infrared spectrum.

Infrared (IR) light is electromagnetic radiation with longer wavelengths than those

of visible light, extending from the nominal red edge of the visible spectrum at

0.74micrometres (µm) to 0.3 mm. This range of wavelengths corresponds to a frequency range

of approximately 430 down to 1 THz, and includes most of the thermal radiation emitted by

objects near room temperature. Infrared light is emitted or absorbed by molecules when they

change their rotational-vibrational movements. The existence of infrared radiation was first

discovered in 1800 by astronomer Herschel.

Infrared light can be split into three categories:

Fig 1Electromagnetic spectrum

Near-infrared (near-IR) is closest to visible light, near-IR has wavelengths that range

from 0.7 to 1.3 microns, or 700 billionths to 1,300 billionths of a meter.Mid-infrared (mid-IR) -

4

Mid-IR has wavelengths ranging from 1.3 to 3 microns. Both near IR and mid-IR are used by a

variety of electronic devices, including remote controls. Thermal-infrared (thermal-IR) -

Occupying the largest part of the infrared spectrum, thermal-IR has wavelengths ranging from 3

microns to over 30 microns. The key difference between thermal-IR and the other two is that

thermal-IR is emitted by an object instead of reflected off it[3].

Infrared is used in night vision equipment when there is insufficient visible light to

see. Night vision devices operate through a process involving the conversion of ambient light

photons into electrons which are then amplified by a chemical and electrical process and then

converted back into visible light. Infrared light sources can be used to augment the available

ambient light for conversion by night vision devices, increasing in-the-dark visibility without

actually using a visible light source.

The use of infrared light and night vision devices should not be confused with thermal

imaging which creates images based on differences in surface temperature by detecting infrared

radiation (heat) that emanates from objects and their surrounding environment. Infrared light is

emitted by an object because of what is happening at the atomic level.

Atoms are constantly in motion. They continuously vibrate, move and rotate. Even the

atoms that make up the chairs that we sit in are moving around. Solids are actually in motion!

Atoms can be in different states of excitation. In other words, they can have different energies. If

we apply a lot of energy to an atom, it can leave what is called the ground-state energy level and

move to an excited level. The level of excitation depends on the amount of energy applied to the

atom via heat, light or electricity.

Once an electron moves to a higher-energy orbit, it eventually wants to return to the

ground state. When it does, it releases its energy as a photon -- a particle of light. You see atoms

releasing energy as photons all the time. For example, when the heating element in a toaster turns

bright red, the red color is caused by atoms excited by heat, releasing red photons. An excited

electron has more energy than a relaxed electron, and just as the electron absorbed some amount

of energy to reach this excited level, it can release this energy to return to the ground state. This

emitted energy is in the form of photons (light energy). The photon emitted has a very specific

wavelength (color) that depends on the state of the electron's energy when the photon is released.

5

Anything that is alive uses energy, and so do many inanimate items such as engines and

rockets. Energy consumption generates heat. In turn, heat causes the atoms in an object to fire off

photons in the thermal-infrared spectrum. The hotter the object, the shorter the wavelength of the

infrared photon it releases.

6

CHAPTER 2

IMAGE ENHANCEMENT

These signals can be conveniently represented and manipulated as matrices containing

the light intensity or color information at each sampled point. When the acquired digital image is

not fit for a prescribed use, image enhancement techniques may be used to modify the image.

According to Gonzales and Woods, the principal objective of enhancement techniques is to

process an image so that the result is more suitable than the original image for a specific

application. So, the definition of image enhancement is a fairly broad concept that can

encompass many applications[4].

The aim of image enhancement is to improve the interpretability or perception of

information in images for human viewers, or to provide `better' input for other automated image

processing techniques. Unfortunately, there is no general theory for determining what `good’

image enhancement is when it comes to human perception. If it looks good, it is good! However,

when image enhancement techniques are used as pre-processing tools for other image processing

techniques, then quantitative measures can determine which techniques are most appropriate.

The principal objective of enhancement is to process an image so that the result is more suitable

than the original image for a specific application

More usually, however, the image enhancement process seeks to enhance the apparent

visual quality of an image or to emphasize certain image features. The benefactor of image

enhancement either may be a human observer or a computer vision program performing some

kind of higher-level image analysis, such as target detection or scene understanding. The two

simplest methods for image enhancement involve simple histogram-modifying point operations

or spatial digital filtering. More complex methods involve modifying the image content in

another domain, such as the coefficient domain of a linear transformation of the image. This

works by collecting the tiny amounts of light, including the lower portion of the infrared light

spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point

that we can easily observe the image.

7

2.1 THERMAL IMAGING

Thermography is the use of an infrared imaging and measurement camera to "see" and

"measure" thermal energy emitted from an object.

Thermal images, or thermo grams, are actually visual displays of the amount of infrared

energy emitted, transmitted, and reflected by an object. Because there are multiple sources of the

infrared energy, it is difficult to get an accurate temperature of an object using this method. A

thermal imaging camera is capable of performing algorithms to interpret that data and build an

image. Although the image shows the viewer an approximation of the temperature at which the

object is operating, the camera is actually using multiple sources of data based on the areas

surrounding the object to determine that value rather than detecting the actual temperature. This

phenomenon may become clearer upon consideration of the formula Incident Energy = Emitted

Energy + Transmitted Energy + Reflected Energy where Incident Energy is the energy profile

when viewed through a thermal imaging camera. Emitted Energy is generally what is intended to

be measured. Transmitted Energy is the energy that passes through the subject from a remote

thermal source. Reflected Energy is the amount of energy that reflects off the surface of the

object from a remote thermal source.

Thermal, or infrared energy, is light that is not visible because its wavelength is too long

to be detected by the human eye; it's the part of the electromagnetic spectrum that we perceive as

heat unlike visible light, in the infrared world, everything with a temperature above absolute zero

emits heat. Even very cold objects, like ice cubes, emit infrared. The higher the object's

temperature, the greater the IR radiation emitted.

Infrared allows us to see what our eyes cannot. Infrared thermograph), cameras produce

images of invisible infrared or "heat" radiation and provide precise non-contact temperature

measurement capabilities. Nearly everything gets hot before it fails, making infrared cameras

extremely cost-effective, valuable diagnostic tools in commercial vehide enforcement

applications.

High definition (or high resolution) thermal imaging refers to the fine detail and clarity of

a thermal image. This means it contains a large number of pixels per unit of area. In this case, a

thermal imaging camera taking a high definition photo means you will find smaller problems at

greater distances. You can find significant problems that could be missed with a lower resolution

8

thermal imaging camera. More pixels mean greater temperature measurement accuracy,

particularly for small objects. This technology operates by capturing the upper portion of the

infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light.

Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or

buildings[5].

2.1.1 EMISSIVITY

Emissivity is a term representing a material's ability to emit thermal radiation. Each

material has a different emissivity, and it can be difficult to determine the appropriate emissivity

for a subject. A material's emissivity can range from a theoretical 0.00 (completely not-emitting)

to an equally-theoretical 1.00 (completely emitting); the emissivity often varies with

temperature. An example of a substance with low emissivity would be silver, with an emissivity

coefficient of .02. An example of a substance with high emissivity would be asphalt, with an

emissivity coefficient of .98.

A black body is a theoretical object which will radiate infrared radiation at its contact

temperature. If a thermocouple on a black body radiator reads 50 °C, the radiation the black body

will give up will also be 50 °C. Therefore a true black body will have an emissivity of 1.

Since there is no such thing as a perfect black body, the infrared radiation of normal

objects will appear to be less than the contact temperature. The rate (percentage) of emission of

infrared radiation will thus be a fraction of the true contact temperature. This fraction is called

emissivity.

2.3 TYPES OF RANGES:

Depending upon the way it is implement it is broadly classified into two types there are

Biological Night Vision, Technical Night Vision. Be it biological or technical Night Vision it is

based on the two Night Vision Approaches

(a) Spectral range

(b) Intensity range

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2.3.1 SPECTRAL RANGE

Night-useful spectral range techniques make the viewer sensitive to types of light that

would be 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 well into the infrared and/or ultraviolet compared to

humans, enough to help them see in conditions humans cannot.

2.3.2 INTENSITY RANGE

Sufficient 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 conditions.

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 or the eyelids), more rods

than cones (or rods exclusively) in the retina, a tapetum lucidum, and improved neurological

filtering. 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.

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Chapter 3

NIGHT VISION DEVICE

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 users. 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. Many NVDs also include sacrificial lenses. IR illuminators and

telescopic lenses.

fig :night vision binocular

NVDs are mounted appropriately for their specific purpose, with more general-purpose

devices having more mounting options. For instance, the AN/PVS-I 4 is a monocular night

vision device in use with the US military as well as by civilians. It may be mounted on the user's

head for hands free use with a harness or helmet attachment, either as a monocular device, or in

aligned pairs for binocular "night vision goggles" which provide a degree of depth perception as

do optical binoculars. The AN/PVS-I4 may also be attached to a rifle using a Pica tinny rail, in

front of an existing telescopic or red dot sight, or attached to a single-lens reflex camera. Other

systems, such as the AN/PVS-22 or Universal Night Sight, are designed for a specific purpose,

integrating an image intensifier into, for example, a telescopic sight, resulting in a smaller and

lighter but less versatile system. Night vision devices were first used in World War II, and came

into wide use during the Vietnam War. The technology has evolved greatly since their

introduction, leading to several "generations" of night vision equipment with performance

increasing and price decreasing. There are many different variables that can affect the distance

you can see with a Night Vision device. First, what are you trying to see? Are you looking for

11

another boat on the water or are you looking for a rabbit in the woods? The larger the object the

easier it is to see. Plus, are you trying to see details (what we call recognition range) or are you

just trying to see if something is there? Maybe you will just see the movement, but won’t be able

to determine 100% who or what it is. This is called “detection range”. A second variable is

lighting conditions. The more ambient light you have (starlight, moonlight, and infrared light)

the better and further you will be able to see. You can always see further on a night where the

moon and stars are out, then if it is cloudy and overcast. We typically state that you can tell the

difference between a male and a female or a dog and a deer at about 75 to 100 yards. However, if

you were looking across an open field and there was a half-moon out you could see a barn or a

house 500 yards away.

Normally handheld or mounted on a weapon, scopes are monocular (one eye-piece).

Since scopes are handheld, not worn like goggles, they are good for when you want to get a

better look at a specific object and then return to normal viewing conditions.

While goggles can be handheld, they are most often worn on the head. Goggles are

binocular (two eye-pieces) and may have a single lens or stereo lens, depending on the model.

Goggles are excellent for constant viewing, such as moving around in a dark building.

Cameras with night vision technology can send the image to a monitor foe display or to a

VCR for recording. When night-vision capability is desired in permanent location, such as on a

building or as part of the equipment in a helicopter, cameras are used. Many of the newer

camcorders have night vision built right in.

12

CHAPTER 4

Working of night vision devices

Night Vision technology consists of two major types: image intensification (light amplification)

and thermal imaging (infrared).

4.1 IMAGE INTENSIFICATION (LIGHT AMPLIFICATION)

Fig image intensification

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 its 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

13

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. 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.

When the electrons from the photo cathode hit the first electrode of the MCP, they are

accelerated into the glass micro channels by the 5,000-V bursts being sent between the electrode

pair. As electrons pass through the micro channels, they cause thousands of other electrons to be

released in each channel using a process called cascaded secondary emission. Basically, the

original electrons collide with the side of the channel, exciting atoms and causing other electrons

to be released. These new electrons also collide with other atoms, creating a chain reaction that

results in thousands of electrons leaving the channel where only a few entered. An interesting

fact is that the micro channels in the MCP are created at a slight angle (about a 5-degree to 8-

degree bias) to encourage electron collisions and reduce both ion and direct-light feedback from

the phosphors on the output side.

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.

14

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.

4.2.1THERMAL IMAGING SYSTEM:

A special lens focuses the infrared light emitted by all of the objects in view. The focused

light is scanned by a phased array of infrared-detector elements. The detector elements create a

very detailed temperature pattern called a thermo gram. It only takes about one-thirtieth of a

second for the detector array to obtain the temperature information to make the thermo gram.

Fig: The basic components of a thermal-imaging system

This information is obtained from several thousand points in the field of view of the detector

array.

1. The thermo gram created by the detector elements is translated into electric impulses.

2. 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.

3. 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.

4.3 TYPES OF THERMAL IMAGING DEVICES

There are two common types of thermal-imaging devices:

1. Un-cooled Thermal Imaging Devices

2. Cryogenically cooled Thermal Imaging Devices

15

4.3.1 UN-COOLED THERMAL IMAGING DEVICES

This is the most common type of thermal-imaging device. The infrared-detector elements are

contained in a unit that operates at room temperature. This type of system is completely quiet,

activates immediately and has the battery built right in.

4.3.2 CRYOGENICALLY COOLED THERMAL IMAGING DEVICES

More expensive and more susceptible to damage from rugged use, these systems have the

elements sealed inside a container that cools them to below 32 F (zero C). The advantage of

such a system is the incredible resolution and sensitivity that result from cooling the elements.

Cryogenically-cooled systems can "see" a difference as small as 0.2 F (0.1 C) from more than

1,000 ft (300 m) away, which is enough to tell if a person is holding a gun at that distance!

While thermal imaging is great for detecting people or working in near-absolute darkness, most

night-vision equipment uses image-enhancement technology.

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CHAPTER 5

GENERATIONS

5.1 GENERATION 0

The earliest (1950's) night vision products were based on image conversion, rather than

intensification. They required a source of invisible infrared (IR) light mounted on or near the

device to illuminate the target area. The first night vision devices, the MI and M3 infrared night

sighting devices, also known as the "sniperscope" or "snooperscope", were introduced by the US

Army in World War 11, and also used in the Korean War, to assist snipers. 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

to accelerate the electrons. Parallel development of night vision systems by AEG occurred in

Nazi Germany, and by the end of World War II, it had equipped approximately 50 Panther tanks,

which saw combat on both the Eastern and Western Fronts, and produced the "Vampire" man-

portable system for infantry soldiers equipped with Sturmuewehr 44 assault rifles.

5.2 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.

Incoming light is collimated by fiber optic plates before impacting a photocathode t

which releases electrons, which in turn impact a phosphor screen. The excited screen emits green

light into a second fiber optic plate, and the process is repeated. The complete process is repeated

three times providing an overall gain of 10,000.

The key developments in this generation were

1. Vacuum Tube Technology

2. Full Moon Operation

3. Amplification: 1,000

4. Operating Life: 2,000 Hours

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5.3 GENERATION 2

The micro channel 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.

Second-generation image intensification significantly increased gain and resolution by

employing a microchannel plate. Figure 2 depicts the basic configuration. [These two sentences

could have been combined: "Figure2 depicts how second-generation image ... plate."] The

microchannel plate is composed of several million microscopic hollow glass channels fused into

a disk. Each channel, approximately 0.0125 mm in diameter, is coated with a special

semiconductor which easily liberates electrons. A single electron entering a channel initiates an

avalanche process of secondary emission, under influence of an applied voltage, freeing

hundreds of electrons. These electrons, effectively collimated by the channel, increase the

resolution of the device. With additional electron optics, details as fine as 0.025 mm can be

realized (half the diameter of a human hair).

Current image intensifiers incorporate their predecessor's resolution with additional light

amplification. The multialkali photocathode is replaced with a gallium arsenide photocathode;

this extends the wavelength sensitivity of the detector into the near infrared. The moon and stars

provide light in these wavelengths, which boosts the effectively available light by approximately

30%, bringing the total gain of the system to around 30,000. The apparent lighting of the

landscape on a dark night is comparable to what the unaided eye would see on a clear winter

night with fresh snow on the ground and a full moon.

The key developments in this generation were

1. First Micro channel Plate (MCP) Application

2. One-Quarter Moon Operation

3. Amplification: 20,000

4. Operating Life: 2,500 Hours

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5.4 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.

The key developments in this generation were

1. Improved MCP & Photocathode

2. Starlight Operation

3. Amplification: 40,000

4. Operating Life: 10,000 Hour

5.5 GENERATION 4

For a good explanation of this commonly misunderstood advancement in night vision

technology.

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.

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5.5.1GENERATION 4 OVER GENERATION 3:

GEN 3 OMNI IV GEN 4 % Improvement

Photo response 1800 1800 -

Signal-to-noise ratio 21.0 25.0(ground) 20% higher

26.0(air) 24% higher

Resolution (Ip/mm) 64 64 -

Halo(mm) 1.25 0.75 40%smaller

Reliability(hours) 10000 10000 -

CHAPTER 6

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APPLICATIONS

Common applications for night vision include:

6.1 MILITARY

Night vision system development began in World War II and has become a critical

component of modern warfare. The ability to see in nighttime conditions allows military

maneuvers and a potential advantage to the forces equipped with this technology. These night

vision systems rely on the very low light levels of starlight and night sky illumination (called

"atmospheric nightglow”) to help image the targeted scene and its surroundings.

When military ground transport vehicles (trucks, tanks, armored personnel carriers,

HUMVEE's) need to operate in total darkness, their drivers can employ Enhanced Vision

Systems (EVS) featuring short wave Infrared (SWIR) illumination and Goodrich short wave

infrared night vision camera systems to navigate covertly in hostile territory. Unlike Mid wave

infrared (MWIR) and Long wave Infrared (LWIR), SWIR cameras can image through the

windshield and thus be mounted in the driver's compartment for a "driver's eye" view of the way

ahead. SWIR cameras can also be integrated into ruggedized exterior housings. Most modern

tanks are fitted with three optical systems: driving, aiming, and commander sights. There is no

clear preference in commander sights at present, different systems meeting different needs. Some

armies use narrow field of view systems similar to image intensifier gunner sights; others prefer

wide field of view systems similar to driving sights. In the future, demands for commander sights

with increased range are likely to cause a switch to thermal imagers.

6.2 HUNTING

The advancement of night vision technology has been improved the hunting in the

night. The hunting of some animal is possible only in night, as the animal come outside of

their shelter at that time. With the advancement of night vision the hunting of many animal is

been easy. The hunting of deer is been easy by wearing the night goggles.

6.3 LAW ENFORCEMENT

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Law enforcement has used this to discover items that have been hidden by criminals, including

money, drugs and bodies. Also, recent changes to areas such as walls can be seen using thermal

imaging, which has provided important clues in several cases.

6.4WILDLIFE OBSERVATION

The national geographic and the discovery channel show the night picture of the animal with the

help of the night vision goggles. The night vision goggles are being used by the travelers of the

discovery channel who discovers the animals and observe the wildlife at night time.

6.5 SURVEILLANCE

Night vision camera can be added to your existing wired or wireless security camera systems to

give you the footage you need in any lighting situation. Taking advantage of new advances in

night vision technology, security cameras have become much more cost effective in recent years,

and have been applied to home, business, and law enforcement surveillance. Night vision is

especially useful for outdoor home security cameras, allowing you to monitor your property

without the need to install lighting. In a man-overboard situation, it is imperative that visual

contact with the fallen person be maintained throughout. The night vison goggles is invaluable

here, particularly when the event occurs at night or in poor visibility conditionsWired and

wireless night vision cameras can also be indoor surveillance cameras used to monitor areas with

inconsistent lighting, like a garage or basement. Just hook a night vision camera up to your

CCTV DVR and you'll be ready to record video in even the darkest parts of your home or

business.

6.6 NAVIGATION

Since infrared radiation is emitted by all objects, a thermal imager is able to “see” the

environment regardless of lighting conditions. This means that, unlike alternative night-vision

equipment such as Near-Infrared (NIR) Laser Systems and Night Vision Devices (NVDs), a

thermal imager gives clear uninhibited vision in complete darkness and dense fog, making it an

ideal marine navigational tool. The night vision goggles allows you to “see” even when no sight

is possible. Floating debris, vessels, rocks, buoys and other structures are clearly visible even in

complete darkness. These systems are intended for spotting missiles and aircraft (including sea-

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skimming) on the horizon. They usually employ CMT infrared detectors, such as the M3 RPY.

Sometimes these systems are wrongly called thermal radars.

CONCLUSION

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The original purpose of night vision was to locate enemy targets at night. It is still used

extensively by the military for that purpose, as well as for navigation, surveillance and targeting.

Police and security often use both thermal- imaging and image-enhancement technology,

particularly for surveillance. Hunters and nature enthusiasts use NVDs to maneuver through the

woods at night.

Detectives and private investigators use night vision to watch people they are assigned to

track. Many businesses have permanently-mounted cameras equipped with night vision to

monitor the surroundings.

A really amazing ability of thermal imaging is that it reveals whether an area has been disturbed

-- it can show that the ground has been dug up to bury something, even if there is no obvious

sign to the naked eye. Law enforcement has used this to discover items that have been hidden by

criminals, including money, drugs and bodies. Also, recent changes to areas such as walls can be

seen using thermal imaging, which has provided important clues in several cases.

Many people are beginning to discover the unique world that can be found after darkness falls. If

you're out camping or hunting a lot, chances are that night-vision devices can be useful to you --

just be sure to get the right type for your needs.

REFERENCES

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[1]Walter, G.D. (Ed). “The Eyes and vision”, chapter 12, handbook of optics. (McGraw Hill

Book Company)

[2]Bhabatosh Chanda and Dwijest Dutta Majumder, 2002, “History of Night Vision Devices”,

London, pp. 397- 400, Dec. 2005

[3]R.W.Jr. Weeks, (1996),”Fundamental of electromagnetic spectrum”, Bellingham: SPIE press

[4]J. Silverman and V. E. Vickers “Display and enhancement of infrared images“, Editor M. A.

Karmic, Electro-Optical Displays Dec 1992, pp.585-651, Marcel Dekker Inc.

[5]A.K Jain, Fundamental of digital image processing. Englewood Cliffs, NJ: prentice Hall, 1989

[6]B. Lianfa, L. Xing, C. Qian, and Z. Baomin, “The hardware design of a real-time Infrared

image enhancement system,” IEEE Int. Conf. Neural Networks & Signal Processing. Dec. 2003,

pp. 1009-1012

[7]Z. Salcic and J. Sivaswamy, “Thermal imaging,” Real-Time Imaging, Vol.5, 1999, pp. 385-

395

[8]L. Xiying, N. Guqiang, C. Yanmei, P. Tian, and Z. Yanli, “Thermal imaging and emissivity,“

Proc. Spie, Conf. Vol. 3561, 1998, pp. 293-299

[9]Task, H.L., (1992).”Night Vision Devices.” In Visual Problems in Night Operations (pp. 7-1 –

7-8), NATO Advisory Group for Aerospace Research and Development, Neuilly-sur-Seine,

France.

[10]A. Torre, A. Peinado, J. Segura,J. Perez-Cordoba. Benitez, and A. Rubio, “image

intensification system,” IEEE light amplification system, Vol. 13, Issue 3, May 2005, pp.355-

366.

[11]A. N. Netravali and B. G. Haskell, “Thermal imaging devices,” New York: Plenum,1988

[12] S. M. Pizer, et al., “generation of night vision goggles,” Computer. Vision, Graphics and

night vision devices, Vol. 39, pp. 355-368, 1987

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[13] H. V. Henderson and S. R. Searle, applications of night vision devices” , Crawford Hill

Laboratory 791 Holmdel-Keyport Rd., Holmdel, NJ 0773, vol. 9, pp. 271–288, Nov 1981.

[14]Angel Lozano and Constantine’s Papadis, “generation of night vision binoculars”, IEEE

night vision technology, VOL. 50, NO. 1, JANUARY 2002

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