"Night Vision” is that technology that provides us with the miracle of vision in total darkness and the improvement of vision in low light environments.

The most common methods as described below are

 Low-Light Imaging, Thermal Imaging

Intensified SLR camera operational schematic

Works in 2 different ways:1.Image enhancement- This works by collecting the tiny amounts of

light including the lower portion of the infrared light spectrum, those are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.( low light imaging)

2.Thermal imaging- This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.

Thermal imaging operates by capturing the upper portion of the infrared light spectrum

Today, the most popular and well known

method of performing night vision is based on the use of image intensifiers.

Image intensifier tube:An electro-optical device which converts photons to electrons, amplifies them, then converts them back to photons so the user can see at light levels that are normally too low.

Low light imaging:

How they work: This method of night vision amplifies the available light to achieve better vision. An objective lens focuses available light (photons) on the photocathode of an image intensifier. The light energy causes electrons to be released from the cathode which are accelerated by an electric field to increase their speed (energy level). These electrons enter holes in a micro channel plate and bounce off the internal specially-coated walls which generate more electrons as the electrons bounce through. This creates a denser “cloud” of electrons representing an intensified version of the original image.

Image intensifier tube

Different from low-light imaging methods of night vision (which require some ambient light in order to produce an image), thermal imaging night vision methods do not require any ambient light at all.

They operate on the principle that all objects emit infrared energy as a function of their temperature. In general, the hotter an object is, the more radiation it emits. 

A color thermal image of dog

Black and white thermal image of docked boat

How thermal imaging works

Generation 0 – uses active infrared.

This means that a projection unit called an IR illuminator is attached to the NVD.

Generation 1 – uses passive infrared.

Once dubbed Starlight by the U.S. army, these NVDs use ambient light provided by the moon and stars to augment the normal amounts of reflected infrared in the environment.

Generation – 2 –. The biggest gain in

generation 2 is the ability to see in extremely low light conditions, such as moonless night. This increased sensitivity is due to the addition of the micro channel plate to the image-intensifier tube

Generation – 3 – The latest and greatest NVD technology, generation 3 is currently used by the U.S. military

They have even better resolution and sensitivity. This is because the photo cathode is made using gallium arsenide, which is very efficient in converting photons to electrons.

Scopes - Normally handheld or mounted on a weapon, scopes are monocular

Goggles - While goggles can be handheld, they are most often worn on the head. Goggles are binocular 

Cameras - 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 or as part of the equipment in a helicopter, cameras

.

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

images

Think of what happens when this night vision technology falls into the hands of hijackers or terrorists or rival forces ?

Thus just like other technologies, it’s a boon when used in a right way but poses a curse when misled

Conclusion

1. Unknown author, “Night Vision Devices”. Book Rags. 11/12/2008

http://bookrags.com

2. Unknown author, “Night Vision Goggles”. Global Security. 11/10/2008

<http://www.global securities.org>

3. Unknown author, “How Night Vision Works”. How Stuff Works. 11/11/2008

<http://electronics.howstuffworks.com>

References