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NIGHT VISION

TECHNOLOGY

-BY 09BIT059

(MIHIKA SHAH)

NIGHT VISION

TECHNOLOGY

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INTRODUCTION

The word Night vision itself means the ability

to see in low light conditions.

Humans have poor night vision compared to

many other animals.

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(Contd...)

So we all might have a question in our mind thatis this really possible to see in the dark night?

The answer is..YES, we can see in thedark night using the proper equipment made byusing this technology.

We can see a person standing over 183m away inthe dark night.

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HISTORY

Pre 1940s: Flares and spot lights were used foroperations at night.

Due to the nature of these early night visiondevices (NVD), they gave away tactical positions.

Military scientists began to think of ways toimprove night vision to gain a strategic advantage

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The first night vision devices (NVD) werecreated during World war-II.

Functioned by placing an infrared filter over asearchlight.

Fighters would use special binoculars to see

using the light from the searchlights.

Many problems came from this night vision

method.

EARLYDEVELOPMENT

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A tank fromWorld War II

equipped

with asearch light

used for

nightcombat.

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The night vision is possible because of twoapproaches:

(1) Sufficient spectral range(2) Sufficient intensity range

Two technologies are used for night vision:(1)Thermal Imaging(2)Image Enhancement

HOW DOES IT WORK?

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(Contd)Infrared light is used to visualize the things in

the dark.

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, andred has the least.

Just next to the visible light spectrum is the

infrared spectrum.

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(Contd)

Infrared light can be split into three categories:

Near-infrared (near-IR) Closest to visible light, near-IR has wavelengths

that range 0.7 to 1.3 micron.

Mid-infrared (mid-IR)

Mid-IR has wavelengths ranging from1.3 to 3 microns.Both near-IR and mid-IR are used by a variety of

electronic devices, including remote controls.

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(Contd)

Thermal-infrared (thermal-IR)

Occupying the largest part of the infraredspectrum, thermal-IR has wavelengthsranging from 3 microns to over 30 microns.

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THERMAL IMAGING

A special lens focuses the infrared light emittedby all of the objects in view.

The focused light is scanned by a phased array ofinfrared-detector elements.The detector elements create a very detailedtemperature pattern called a thermogram.It only takes about one-thirtieth of a second for thedetector array to obtain the temperatureinformation to make the thermogram.

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(Contd)

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(Contd)

This information is obtained from severalthousand points in the field of view of the detectorarray.

The thermogram created by the detectorelements is translated into electric impulses.

The impulses are sent to a signal-processing unit,a circuit board with a dedicated chip thattranslates the information from the elements intodata for the display.

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(Contd)

The signal-processing unit sends theinformation to the display, where it appears as

various colors depending on the intensity ofthe infrared emission.

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

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In day light In dark night

Using thermal imaging

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IMAGE ENHANCEMENT

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An image-intensifier tube is used 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-intensifiertube.

The image-intensifier tube has a photocathode,which is used to convert the photons of light energy

into electrons.

(Contd)

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(Contd)

A Microscopic plate(MCP) is a tiny glass disk thathas millions of microscopic holes in it.

The MCP is contained in a vacuum and has metalelectrodes on either side of the disc.

When the electrons from the photo cathode hit the

first electrode of the MCP, they are accelerated intothe glass micro-channels by the 5,000-V bursts being

sent between the electrode pair.

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As electrons pass through the micro channels, they

cause thousands of other electrons to be released ineach channel using a process called cascadedsecondary emission.

At the end of the image-intensifier tube, theelectrons hit a screen coated with phosphors.

These electrons maintain their position in relationto the channel they passed through, which providesa perfect image since the electrons stay in the same

alignment as the original photons.

(Contd..)

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(Contd)

The energy of the electrons causes the phosphorsto reach an excited state and release photons.

These photons create the image on the screen.

The green phosphor image is viewed throughanother lens, called the ocular lens, which allowsyou to magnify and focus the image.

The NVD may be connected to a monitor to

display the image.

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GENERATIONS

NVDs have been around for more than 50 years.They are categorized by generation.

Each substantial change in NVD technology

establishes a new generation.

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(Contd)

GENERATION- 0 Created by US Army. Uses active infrared.

A projection unit called IR illuminator is attachedwith NVD. Use anode in conjunction with cathode to accelerate

the electrons. Problems : acceleration causes distortion of imageand reduction of the life of the tube. Duplicated by the hostile nations.

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(Contd)

GENERATION- 1 Uses passive infrared. Uses ambient light provided by the moon and the

stars.Doesnt require a source of projected infrared light.Doesnt work well on cloudy or moonless nights.

Uses same image-intensifier tube technology asGeneration-0. Same problems as faced by the Generation-0.

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(Contd)

GENERATION- 2 Offer improved resolution and performance over

Generation-1 devices. Considerably more reliable. Able to see in extreme low light conditions due tothe addition of microchannel plate(MCP) to theimage-intensifier tube.The images are less distorted and brighter.

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(Contd)

GENERATION- 3 Currently used by the US Army.

Better resolution and sensitivity. Photocathode is made up of Gallium Arsenide-efficient of converting photons to electrons. MCP is coated with an ion barrier.Tube life is increased

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(Contd)

GENERATION- 4 Known as filmless and gated technology. Shows significant improvement in both high- andlow-level light environments. No ion barrier in MCP. Reduced background noise. Enhances signal to noise ratio. Images are less distorted and brighter.

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NIGHT VISION DEVICES

It can be splitted in three broad categories:I. ScopesII. GogglesIII. Cameras

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(Contd)

SCOPES

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(Contd)

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

Can not be worn like goggles.

It is good for when you want to get a better look

at a specific object and then return to normalviewing conditions.

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(Contd)

GOGGLES

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While goggles can be handheld, they are mostoften worn on the head.

Goggles are binocular (two eye-pieces) and mayhave a single lens or stereo lens, depending on themodel.

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

(Contd)

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(Contd)

CAMERAS

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(Contd)

Cameras with night-vision technology can sendthe image to a monitor for display or to a VCR for

recording.

When night-vision capability is desired in a

permanent location, such as on a building.

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APPLICATIONS

MilitaryHuntingWildlife observationSurveillanceSecurity

NavigationHidden-object detectionEntertainment

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BMW's Night Visionwith PedestrianDetection systemallows drivers to see

what (or who) is downthe road -- even on thedarkest nights.

AUTOMOBILE

(Contd)

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Dr. Prabhat Ranjan from DA-IICT has used acamera based on Infrared flash in his research on

Sensor Networks in wildlife.

(Contd)

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REFERENCES

http://en.wikipedia.org/wiki/Night_vision

http://electronics.howstuffworks.com

http://carl.sandiego.edu

http://en.wikipedia.org/wiki/Night_visionhttp://electronics.howstuffworks.com/http://carl.sandiego.edu/http://carl.sandiego.edu/http://carl.sandiego.edu/http://carl.sandiego.edu/http://carl.sandiego.edu/http://carl.sandiego.edu/http://carl.sandiego.edu/http://electronics.howstuffworks.com/http://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/wiki/Night_vision

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THANK YOU