Night Vision Technology - Copy

8/2/2019 Night Vision Technology - Copy

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BY

SYED SARWAR IMAM 08301A0594


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Night Vision Technology, by definition, allowsone tosee inthe dark.

Originally developed for military use,ithasprovided the United Stateswith a

strategic advantage,the value ofwhichis measured inlives.

INTRODUCTION


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To understand night vision,itisimportantto understand aboutlight..

The amountof energyin a lightwave is related toitswavelength.

Ofthe visible light, violethas more energy and red the least.

Nextto visible lightisinfrared spectrum, broadly classified as

NEAR-INFRARED: Ranging 0.7 to 1.3 microns.

MID-INFRARED : Ranging 1.3 to 3 microns.

THERMAL-INFRARED: Ranging 3 to 30 microns.


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WORKING OFNIGHT VISION


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HOW DOES THERMAL IMAGING WORK????????

Components used inthermalimaging are as follows:

A speciallensthat

focusesthe infraredlight emitted by allof

the objectsin view.

Aninfrared detector.

Signalprocessing unit. A display device.


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Its quite easytosee everything

duringthe day.

..but atnight,you cansee very

little.

Thermalimagingletsyou see again.


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TYPES OF THERMAL IMAGING DEVICES..

UN-COOLED: The unitoperates

at room temperature.

UN-COOLED: The unitoperates

at room temperature.

CRYOGENICALLY COOLED: The

unit kept at a temperature

below 32 deg. F.

CRYOGENICALLY COOLED: The

unit kept at a temperature

below 32 deg. F.


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THEN WHAT ABOUT IMAGE ENHANCEMENT?????

Image enhancementsystems are normally called NIGHT VISION DEVICES (Nvds).

NVDs relyon a specialtube, called animage-intensifiertubeto collect and amplify

infrared and visible light.

The image-intensifier tube changesphotonsto electrons and back again..


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HOW DOES IMAGE ENHANCEMENT WORK

A conventionallens, called objective lens, capturesthe ambientlight and some nearinfrared light.

The gathered lightissenttothe image intensifier tube.

The image-intensifier tube changesphotonsto electrons and back tophotons again.

The image-intensifier tube consistsof:

1) A photo-cathode which convertsphotonsto electrons.2) A microchannelplatefor multiplicationof electrons.

3) A phosphorscreenthat releasesphotons and creates a green image

viewed throughocularlens and displayed on a monitor.


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Why doNV devices alwaysshow

imagesinhuesofgreen?

The screenwaspurposefully colored

green due tothe scientific factthatthehuman eye can differentiate more

shadesofgreenthan anyother color.


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GENERATIONS OFNIGHT VISION PRODUCTS

There are 5 generationsofnight visionproducts. They are as follows:

GENERATION 0: Night visionproducts developed in early 1950s.

GENERATION1:Advanced devicesproduced in 1960s.

GENERATION 2:Introductionof MCP in 1970s.

GENERATION3:Newer versionsof MCPswere developed inlate 1970s and early 1980s.

GENERATION4:Extended partofGEN3 formsthisgeneration.

GENERATION-0

The earliestnight visionproductswere based onimage conversion rather thanimageintensification. They required a source ofinvisible IR light mounted near or onthe device

toilluminate the target area.


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GENERATION-1

Theyhave 3 image intensifier tubes connected inseries.

Incominglightis collimated by fiber optic plates.

The collimated lightisimpacted on a photocathode which releases electrons,

whichinturnimpact a phosphor screen.

The excited screen emitsgreenlightintothe nextplate and process repeats.

A gainof 10,000 wasobtained inthisgeneration.


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GENERATION-2

The micro channelplate (MCP) electron multiplier prompted GEN2 development.

The gainprovided by MCP eliminated the need for back-to-back tubesthereby

improvingthe image size and image quality.

Hand-held and helmet mounted goggleswere developed inthisgeneration.


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GENERATION-3

Two major advancements characterized developmentofGEN3:

Multi alkaliphotocathode was replaced byGallium Arsenide(GaAs)photocathode. This enabled detectionofobjects atgreater distances

under much darker conditions.

The ion-barrier film on MCP increased the operationallife ofthe tube from

2000 hoursto 10,000 hours.


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GENERATION-4

GEN-3 withincreased performance,provided by ITT known as OMNIis

developed under thisgeneration.

GEN-3 devices may be further defined as OMNI 3,4,5 etc..


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CHARACTERISTICS OFNIGHT VISION

A. Textures,lightanddark: Objectsthat appear light duringthe day

buthave a dullsurface may appear darker,throughthe night visionunit.

B. Fogandrain: Night visionis very responsive to reflective ambient

light;therefore light reflectingoffof fogor heavy rain causes much

more lighttogotowardsthe night vision unit.

C. Blackspots: A few black spotsthroughoutthe image area are also

inherent characteristicsof allnight visiontechnology. An example with

black spotsisshown below..


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EQUIPMENT AND APPLICATIONS

Night Vision equipment can be splitintothree broad categories:-

Scopes:- Normallyhandheld or mounted on a weapon,scopes are monocular

(one eye-piece).


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GOGGLES:- Goggles can be handheld, butthey are mostoftenwornonthe

head. Goggles are binocular (two eye-pieces) and mayhave a single lensor

stereolens dependingonthe model.


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CAMERAS:- Cameraswithnight-visiontechnology cansend the image to a monitor

for displayor to a VCR for recording. Cameras are used whennight-vision capabilityis

desired in a permanentlocation,such ason a building.


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Military

Security

APPLICATIONS

Common applications for night visioninclude


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