The glasses helps to see during night

2. Topics:-
INTRODUCTION
HOW DOES IT WORKS
GENERATION OF DEVICES
NIGHT VISION DEVICES
USES OF NIGHT VISION TECHNOLOGY IN AUTOMOBILES
MERITS AND DEMERITS
CONCLUSION

3. Introduction
Night vision is the ability to see in low-light
conditions.
Humans have poor night vision compared to many
nocturnal animals, in part because the human eye
lacks a Tepetum lucidum.
With the proper night-vision equipment, we can
see a person standing over 200 yards (183 m) away
on a moonless, cloudy night.

4. HOW DOES IT WORKS
 Two technologies are used for night vision:
(1)Thermal Imaging.
(2)Image Enhancement.
Infrared light is used to visualize the things in the
dark.
Just next to the visible light spectrum is the
infrared spectrum.

5.  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.
 Thermal-infrared (thermal-IR) –
Occupying the largest part of the infrared
spectrum, thermal-IR has wavelengths ranging from 3 microns to
over 30 microns

7. 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.
 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.
 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

9. IMAGE ENHANCEMENT
 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.
 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.
 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

10.  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.
 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
.

12. Image enhancement Thermal imaging

13. 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

14. 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.

15. 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

16. 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 micro channel plate(MCP) to the image-
intensifier tube.
The images are less distorted and brighter

17. 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.

18. 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

20. NIGHT VISION DEVICES
It can be splitted in three broad categories:
scopes cameras goggles

21. NVD IN
AUTOMOBILES
 It is a system to increase a vehicle driver's visibility in darkness or poor weather
beyond the reach of the vehicle's headlights .
 In this system Light waves [infrared (IR) ] are emitted by source ; a special
cameras collect small amounts reflected light and amplify it to generate display on
cluster .

22. APPLICATIONS
Military
Hunting
Wildlife observation
Surveillance
Security
Navigation
Hidden-object detection

23. Merits:
Distant vision is possible.
Detection of objects in absolute darkness.
Less affected by temperature variation.
Demerits:
The only disadvantage is that the Initial cost too high.

24. Conclusion:
Night vision is used to locate an object which is 200 yards
away even in moonless, cloudy night.
The original purpose of night vision is to locate enemy
targets at night.
It is mainly used in military purposes as well as navigation,
surveillance cameras.