NIGHT VISION TECHNOLOGY

NIGHT VISION TECHNOLOGY
NIGHT VISION TECHNOLOGY
-BY 09BIT059
(MIHIKA SHAH)

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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So we all might have a question in our mind that is this really possible to see in the dark night?
The answer is……..YES, we can see in the dark night using the proper equipment made by using this technology.
We can see a person standing over 183m away in the dark night.

HISTORY
Pre 1940’s: Flares and spot lights were used for operations at night.
Due to the nature of these early night vision devices (NVD), they gave away tactical positions.
Military scientists began to think of ways to improve night vision to gain a strategic advantage

EARLYDEVELOPMENT
The first night vision devices (NVD) were created during World war-II.
Functioned by placing an infrared filter over a searchlight.
Fighters would use special binoculars to see using the light from the searchlights.
Many problems came from this night vision method.

A tank from World War II equipped with a search light used for night combat.

HOW DOES IT WORK?
The night vision is possible because of two approaches:
(1) Sufficient spectral range
(2) Sufficient intensity range
Two technologies are used for night vision:
(1)Thermal Imaging
(2)Image Enhancement

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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, and red has the least.
Just next to the visible light spectrum is the infrared spectrum.

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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 from
1.3 to 3 microns.
Both near-IR and mid-IR are used by a variety of electronic devices, including remote controls.

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

THERMAL 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.

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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 electric impulses.
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.

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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.

In day light
In dark night
Using thermal imaging

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

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A Microscopic plate(MCP) is a tiny glass disk that has millions of microscopic holes in it.
The MCP is contained in a vacuum and has metal electrodes on either side of the disc.
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.

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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.
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.

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The energy of the electrons causes the phosphors to reach an excited state and release photons.
These photons create the image on the screen.
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 a monitor to display the image.

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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GENERATION- 0
Created by US Army.
Uses active infrared.
A projection unit called IR illuminator is attached with NVD.
Use anode in conjunction with cathode to accelerate the electrons.
Problems : acceleration causes distortion of image and reduction of the life of the tube.
Duplicated by the hostile nations.

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GENERATION- 1
Uses passive infrared.
Uses ambient light provided by the moon and the stars.
Doesn’t require a source of projected infrared light.
Doesn’t work well on cloudy or moonless nights.
Uses same image-intensifier tube technology as Generation-0.
Same problems as faced by the Generation-0.

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GENERATION- 2
Offer improved resolution and performance over Generation-1 devices.
Considerably more reliable.
Able to see in extreme low light conditions due to the addition of microchannel plate(MCP) to the image-intensifier tube.
The images are less distorted and brighter.

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

NIGHT VISION DEVICES
It can be splitted in three broad categories:
Scopes
Goggles
Cameras

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SCOPES

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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 normal viewing conditions.

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GOGGLES

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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.

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CAMERAS

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Cameras with night-vision technology can send the 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.

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

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AUTOMOBILE
BMW's Night Vision with Pedestrian Detection system allows drivers to see what (or who) is down the road -- even on the darkest nights.

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Dr. Prabhat Ranjan from DA-IICT has used a camera based on Infrared flash in his research on ‘Sensor Networks in wildlife’.

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

THANK YOU

NIGHT VISION TECHNOLOGY

by Mihika Shah

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