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CHAPTER 1:

INTRODUCTION

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 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.

The first thing you probably think of when you see the words night vision is a spy

or action movie youve seen, in which someone straps on a pair of night vision goggles to find

someone else in dark building on a moonless night. With the proper night-vision equipment,

you can see a person standing over 200 yards(183m) away on a moonless, cloudy night.

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CHAPTER 2:

THE BASICS

2.1 About Infrared 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.

Figure 2.1

Infrared light can be split into three categories:

Near-infrared (near-IR) Closest to visible light, near=IR has wavelengths thatrange from 0.7 to 1.3 microns.

Mid-infrared (mid-IR)MidIR has wavelengths ranging from 1.3 to 3 microns.Both near-IR and mid-IR are used by averiety of electronic devices,including

remote control.

Thermal-infrared (thermal-IR)Occupying the largest part of infrared spectrum,thermal-IR has wavelengths ranging from 3 to 30 microns.

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The key difference between thermal-IR and the two is that thermal-IR is emitted

by an object instead of reflected off it. Infrared light is emitted by an object because of what

is happening at the atomic level

2.2 Atoms:

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. 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. The diagram for atom is shown in fig. 2.2.

Figure: 2.2

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CHAPTER 3:

NIGHT VISION APPROACHES

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 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-IR

or ultraviolet radiation). Some animals can see well into the IR and/or ultraviolet compared to

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

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

eye ball, a larger lens, a larger optical aperture, more rods than cones 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 4:

NIGHT VISION DEVICES

4.1 Definition:

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 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 NVDs are mounted appropriately for their

specific purpose, with more general-purpose devices having more mounting options. For

instance, the AN/PVS-14 is a monocular night vision device in use with the US military as

well as by civilians. It may be mounted on the users 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 do optical binoculars. The

AN/PVS-14 may also be attached to a rifle using picatinny rail, in front of an existing

telescopic or red dont 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.

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4.2 Some devices:

Figure 4.2.1:

Figure 4.2.2: Binocular with the Helmet

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Figure 4.2.3: Binocular with same lens

Figure 4.2.4: Simple Binocular

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CHAPTER 5:

WORKING OF THE NIGHT VISION DEVICES

Night Vision technology consists of two types: Image intensification or

enhancement (light amplification) and thermal imaging.

5.1 Image Enhancement:

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 visible light.

Figure 5.1.1: image-intensifier tube changes photons to electrons and back again

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A conventional lens, called the objective lens, captures ambient light and somenear-infrared light.

The gathered light is sent to the image-intensifier tube. In most NVDs, thepower supply for the image-intensifier tube receives power from two N-cell or

two AA batteries. The tube outputs a high voltage, about 5000v to the image-

tube components.

The image-intensifier tube has a photocathode, which is used to convert thephotons of light energy into electrons.

As the electrons pass through the tube, similar electrons are released fromatoms in the tube, multiplying the original number of electrons by a factor of

thousands through the use of a microchannel plate (MCP) in the tube. An MCP

is a tiny glass disc that has millions of microscopic holes in it, made using fiber-

optic technology. the MCP is contained in vacuum and has metal electrodes on

either side of disc. Each channel is about 45 times longer than it is wide, and it

works as an electron multiplier.

When the electrons from the photocathode hit the first electrode of the MCP,they are accelerated into the glass microchannels by the 5000-V bursts being

sent between the electrode pair. As electrons pass through the microchannels,

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 microchannels 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.

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At the end of the image-intensifier tube, the electrons hit a screen coated withphosphors. 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 ocularlens, which allows you to magnify a focus the image. The NVD may be

connected to an electronic display, such as monitor, or the image may be

viewed directly through the ocular lens.

Figure 5.1.2: Night-vision images are known for their green tint

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5.2Thermal Imaging:

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

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.

The thermogram created by the detector elements is translated into electricimpulses.

The impulses are sent to a signal-processing unit, a circuit board with adedicated chip that translates the information from the elements into data for the

display.

The signal-processing unit sends the information to the display, where it appearsas various colors depending on the intensity of the infrared emission. The

combination of all the impulses from all of the elements creates the image.

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Figure 5.2.1: The basic components of a thermal imaging system

5.2.1 Types of thermal imaging devices:Most thermal imaging devices scan at a rate of 30 times per second. They can

sense temperatures ranging from 4 degrees Fahrenheit (-20 degree Celsius) to 3600F (2000

C), and can normally detect changes in temperature of about 0.4 F (0.2 C).

5.2.1.1 Un-cooled:

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 quite, activates immediately and has the battery built right in.

5.2.1.2 Cryogenically-cooled:

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 (0 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 (0.2 C)

from more than 1000 ft (300 m) away, which is enough to tell if a person is holding a gun at

distance.

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CHAPTER 6:

GENERATIONS

6.1 Generation 0:

The earliest (1950s) night vision products ware 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.

6.2 Generation 1:

The starlight scopes of the 190s (Vietnam Era) have three image

intensifier tubes connected in a series. These systems are larger and heavier then 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.

Figure 6.2 illustrates first-generation night vision. [Not a great topic sentence but it does have

the advantage of calling attention to the figure.] Incoming light is collimated by fiber optic

plates before impacting a photocathode which releases electrons, which in turn impact a

phosphor screen. The excited screen emits green light into a second fiber optic plate, and the

prices is repeated. The complete process is repeated three times providing an overall gain of

10,000.

Figure 6.2: First generation image intensifier

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6.3 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 helmet mounted goggles.

Second-generation image intensification significantly increased gain and

resolution by employing a microchannel plate. Figure 6.3 depicts the basic configuration.

[These two sentences could have been combined: Figure 6.3 depicts how second-generation

image plate.] The microchannel plate is composed of several million microscope hollow

glass channels fused into a disk. Each channel, approximately 0.0125mm in diameter, is

coated with a special semiconductor which easily liberates electrons. A single electron

entering a channel initiates an available 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 0.025mm can be realized (half the diameter of a human hair).

Figure 6.3: Second generation image intensification

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Current image intensifier incorporate their predecessors 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 boost the effectively

available light by approximately 30%, bringing the total gain of the system to around 30,000.

6.4 Generation 3:

Two major advantages 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 10000 (Gen 3), as demonstrated by actual testing and not

extrapolation.

6.5 Generation 4:

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 contacts referred to as Omnibus- abbreviated as OMNI. For each

successive OMNI contact, 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 contracts as of 2006 is OMNI 7.

If youre 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 situation with higher levels of ambient light.

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Figure 6.5: Improvement over Gen 2

6.6 KEY GENERATION DEVELOPMENTS:

GENERATION 1 (Developed in 1969s): Vacuum Tube Technology Full Moon Operation Amplification: 1,000 Operating Life: 2,000 Hours

GENERATION 2 (Developed in 1970s): First Micro channel plate (MCP) Application One-Quarter Moon Operation Amplification: 20,000 Operating Life :2500 Hours

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

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

GENERATION 3 Enhanced (2000s): Improvement in the photocathode and MCP resulted in increased gain and

resolution.

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CHAPTER 7:

CHARACERISTICS OF THE 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.

7.1 Textures, Light and Dark:

Objects that appear light during the day but have a dull surface mayappear

darker, through the night vision unit, than objects that are dark during the day but have a

highly reflective surface. For example, a shinny dark colored jacket may appear brighter than

a light colored jacket with a dull surface.

7.2 Depth Perception:

Night vision does not present normal depth perception.

7.3 Fog and Rain:

Night vision is very responsive to reflective ambient light; therefore, the light

reflecting off of fog or heavy rain cause much more light to go toward the light vision unit

and may degrade its performance.

7.4 Honeycomb:

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

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7.5 Block Spots:

A few black spots throughout the image area 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.

Figure 7.5: Black spots on MCP in intensifier

Do not be concerned if you see this feature it is an inherent characteristics

found in light amplification night vision systems that incorporate a microchannel plate in the

intensifier.

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CHAPTER 8:

Early Attempts at Night Vision Technology

Military tacticians throughout history have seen the advantage of being

able to maneuver effectively under of the cover of darkness. Historically maneuvering large

armies at night at night carried such as risk that it was rarely attempted.

During WW II, the United States, Britain and Germany Worked to

develop rudimentary night vision technology. For example, a useful infrared sniper scope that

used near infrared cathodes coupled to visible phosphors to provide a near infrared image

converter was fielded. A small number, perhaps 300 Sniperscopes, Were shipped to

the Pacific sometime in 1945, but very received very little use. Their range was less than

100 yards, and they were used mainly for perimeter defense. However this device had several

disadvantages. The infrared sniper scope required an active IR searchlight that was so large

had to be mounted on a flatbed truck. This active IR searchlight could be detected be any

enemy soldier equipped with similar equipment. Rifle-mounted scope also required

cumbersome batteries and provided limited range.

However, the infrared sniper scope showed that night vision technology

was on the horizon. Military leaders immediately saw many uses for this technology

beyond sniping at the enemy under cover of darkness. An army equipped with night vision

goggles, helmets, and weapons sight would be able to operate 24 hours a day. Army Corps of

Engineers, for example, would able to bridge and repair roads at night providing a measure of

safety from airborne attack. The next challenge in night vision technology would be the

development of passive systems that did not require IR searchlights that might give away a

soldiers position to the enemy.

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CHAPTER 9:

APPLICATIONS

Common applications for night vision include:

Military Law enforcement Hunting Wildlife observation Surveillance Security Navigation Hidden-object detection Entertainment

Figure 9: This soldier is using DARK INVADER night vision goggles

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

still used to military for that purpose, as well as for navigation, surveillance and targeting.

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

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

woods at night.

A really amazing ability of the thermal imaging is that it reveals whether an

area has been disturbed it can show that ground has been dug to bury something, even if

there is no obvious sign to the naked. Law enforcement has used this to discover items that

have been by criminals, including money, drugs and bodies. Also, recent to area such as walls

can be seen using thermal imaging. Which has provided important clues in several cases.

Detectives and private investigators use night vision to watch people they

are assigned track. Many businesses have the permanently mounted cameras equipped

with night vision to monitor the surroundings.

A really amazing ability of the thermal imaging is that it reveals whether an

area has been disturbed it can show that ground has been dug to bury something, even if

there is no obvious sign to the naked. Law enforcement has used this to discover

items that have been by criminals, including money, drugs and bodies. Also, recent to area

such as walls can be seen using thermal imaging. Which has provided important clues in

several cases.

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CHAPTER 10:

CONCLUSION

The new generation began to discover the unique word that can be

found after darkness falls. Thus in the modern times night vision technology

become a part of our daily life.night vision devices can be useful to you-just be

sure to get the right type of your needs.

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CHAPTER 11:

REFERANCES

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Soc. of America, 38, pp. 196-208, February 1948.

2. Richards, E. A., 'Fundamental limitations in the low light level performance of direct-view

image intensifier systems',Infra-red Physics, 8, pp. 101-15, 1968.

3. Soule, H. V., 'Electro-optical Photography at Low Illumination Levels', (John Wiley, New

York, 1968).

4. Koehler, H., 'Objectives for image converters and image intensifiers', Applied Optics, 7,

pp. 1035-41, June 1968.

5. Richards, E. A., 'Limitations in optical imaging devices at low light levels',Applied Optics,

8, pp. 1999-2005, October 1969.

6. Huxford, R. B., 'Design consideration of large aperture lens systems'. Proc. of Conference

on Electro-Optics, Brighton, pp. 58-70, 1971.

7. Roach, F. E., 'The light of the night sky, astronomical, interplanetary and geophysical',

Space Science Reviews, 3, pp. 512-40, 1964.

8. Guest, A. J., Holmshaw, R. T. and Manley, B. W., 'Channel multiplierplates for imaging

applications',Advances in Electronicsand Electron Physics, 28A, pp. 471-86, 1969.

9. Guest, A. J., 'Channel multiplier plates for image intensification', Milliard Technical

Communications,No. 108, pp. 170-6, November 1970.

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10. Gildea, J., 'Low light level t.v. techniques',Applied Optics, 9, pp. 2230-5, October 1970.

11. Astheimer, R. W. and Schwarz, F., 'Thermal imaging using pyroelectric detectors',

Applied Optics, 7, pp. 1687-95, 1968.

12. Putley, E. H. and Ludlow, J. H., 'Pyroelectric detectors', Proc. Conference on Electro-

Optics, Brighton, pp. 71-7, 1971.

13. Baker, G., Charlton, D. E. and Lock, P. J., 'High performance pyroelectric detectors', The

Radio and Electronic Engineer, 42, pp. 260-4, June 1972.

14. Holeman, B. R. and Wreathall, W. M., 'Thermal imaging camera tubes with pyroelectric

targets', / .Phys. D. {AppliedPhysics), 4, pp. 1898-1909. December 1971.

15. Martin, M. D. and Barkess, G P., 'The Simulation of Night sky Radiation in the SRDE

Dark Tunnel'. SRDE Memorandum, No. Vl/72,1972.