NIGHT VISION TECHNOLOGY Slide layers

Introduction
Types of NVT
Thermal Imaging
Image Enhancement
Performance Attributes
Technical characteristics
Equipments
Applications
Conclusion
References

Introduction
NVT allows us to see in the dark
Originally developed for military use
Now used for site security, surveillance as well as search and rescue
Evolved from bulky optical instruments in lightweight goggles through the advancement of image intensification technology.
Types of night vision
Categorized by generations
Each substantial change NVT establishes a new generation
Categorized into:
Generation-0
Generation-1
Generation-2
Generation-3
Generation-4

Generation-0
Created by US Army
Uses active infrared
A projection unit called IR illuminator is attached
Full moon operation
Use anode in conjunction with cathode to accelerate the electrons
Problems “acceleration causes distortion of image as well as reduction of life of the tube
Also, it was quickly duplicated by the hostile nations

Generation-1 (1960™s)
Uses passive infrared
Uses ambient light provided by the moon and the stars
Don™t require a source of projected infrared light
Don™t work well on cloudy or moonless nights
One quarter moon operation
Uses same image-intensifier tube technology as Generation-0
Same problems as faced by the Generation-0

Generation-2 (1970™s)
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

 

Generation-3 (1990™s)
Currently used by the US Army
Better resolution and sensitivity
Photocathode is made up of Gallium Arsenide
MCP is coated with an ion barrier
Tube life is increased
Generation-4 (2000™s)
Known as filmless and gated technology
Shows significant improvement in both high- and low-level light environments
No ion barrier in MCP
Responds quickly to different lightning conditions
Reduced background noise
Enhances signal to noise ratio
Images are less distorted and brighter

Thermal imaging
This technology operates by capturing upper portion of the infrared light spectrum, which is emitted as heat
Hotter objects emit more of this light than the cooler objects
These elements then create a thermogram
Thermogram electric pulses display data

Thermal imaging
Thermal imaging devices
Two types:
1. Uncooled.
2. Cryogenically cooled.

Great for detecting people or working in near-absolute darkness

Image Enhancement
Image Enhancement
It is also known as Image intensification
Relies on image intensifier tube to collect an amplify infrared and visible light
Lens captures the light which is then sent to image intensifier tube
It has photocathode that converts photons into electrons
When electrons pass through MCP ,more electrons are presented
This causes chain reaction where atoms are released
Electrons reach phosphor screen and photons are released
Those phosphor create green image

Performance Attributes
Sensitivity (photo response)- tube™s ability to detect the available light
Signal- plays a key role in night vision™s performance
Resolution- ability to dissolve detail in the image
Technical Characteristics
Textures, Light and Dark
Depth Perception
Fog and Rain
Honeycomb
Spots
Equipments
Three categories
Scopes
Goggles
Cameras

Equipments
Scopes- monocular, handheld, better look at a specific object and then return to normal viewing conditions.
Goggles- binocular, handheld or worn, excellent for constant viewing
Cameras- send the image to a monitor for display or to a VCR for recording.

 

Applications
Military
Law enforcement
Hunting
Wild life observation
Surveillance
Security
Navigation
Hidden-object detection
Entertainment

Conclusions
Although the term ``night vision'' currently encompasses three distinct technologies, it is the evolution of image intensification technology that first made devices practical and widely used.

Their success was the result of advancements in light amplification and resolution techniques.
References

http://electronics.howstuffworks.com/nightvision3.html
http://www.nightvision.com/military/militaryhome.html
http://www.physics.ohio-state.edu/~wilki...index.html
http://www.atncorp.com/HowNightVisionWorks
http://www.morovision.com/hownightvisionworks.htm
http://www.alanaecology.com/acatalog/Introduction_to_ Nightvision.html