Night Vision

NIGHT VISION TECHNOLOGY

(Night Vision Device)

PROJECT GUIDE PRESENTED BY:

MR. SACHITH RAJAGOPAL Randhir kumar parmar LECTURER CS-B S.O.E,CUSAT

WHAT WE WILL COVER !

What is night vision

Night Vision Approaches

The night vision technology

Working of night vision device

Generations

Usage

Conclusion

References

What is Night Vision ??

Ability to see in dark environment

Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range .

Humans have poor night vision compared to many animals, in part because the human eye does not have a tapetum lucidum

The tapetum lucidum (Latin: "bright tapestry", plural tapeta lucida ) is a layer of tissue in the eye of many animals, that lies immediately behind or sometimes within the retina. It reflects visible light back through the retina, increasing the light available to the photoreceptors. This improves vision in low-light conditions.

Night Vision Approaches

Spectral range :

Night-useful spectral range techniques make the viewer sensitive to types of light that would be invisible to a human observer. Human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals can see well into the infrared and/or ultraviolet compared to humans, enough to help them see in conditions humans cannot.

Intensity range :

Sufficient intensity range is simply the ability to see with very small quantities of light. Although the human visual system can, in theory, detect single photons under ideal conditions, the neurological noise filters limit sensitivity to a few tens of photons even in ideal conditions. Many animals have better night vision than humans do, Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photo detectors.

Night Vision Device

A night vision device (NVD) is an optical instrument that allows

images to be produced in levels of light approaching total darkness.

They are most often used by the military and law enforcement agencies,

but are available to civilian users.

The figure shows night vision goggle

EXAMPLES :

1.

the AN/PVS-14 is a monocular night vision device in use with the US military as well as by civilians. It may be mounted on the user's head for handsfree use with a harness or helmet attachment

2.

Another example is binoculars night vision device.

Binocular telescopes , or binoculars (also known as field glasses), are two identical or mirror-symmetrical

telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.

3.

Another Example is monocular situated on the gun. The figure shows this type of night vision device

Working of Night Vision devices

Night Vision technology consists of two major types:

image intensification (light amplification) and

Thermal imaging(infrared).

IMAGE INTENSIFICATION

It is also called light amplification

It is less expensive than thermal

Light amplification technology takes the small amount of light, such as moonlight or starlight, that is in the surrounding area, and converts the light energy (scientists call it photons), into electrical energy (electrons)

These electrons pass through a thin disk that's about the size of a quarter and contains over 10 million channels.

As the electrons travel through and strike the walls of the channels, thousands more electrons are released.

These multiplied electrons then bounce off of a phosphor screen which converts the electrons back into photons and lets you see an impressive nighttime view even when it's really dark.

All image intensified night vision products on the market today have one thing in common: they produce a green output image

THERMAL IMAGING

CONTINUED….

WORKING OF 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.

Types Of Thermal Imaging Device

There are two common types of thermal-imaging devices:

Un –Cooled

Cryogenically Cooled

Un-Cooled

This is the most common type of thermal-imaging device. The infrared-detector elements are contained in a unit that operates at room temperature. This type of system is completely quiet, activates immediately and has the battery built right in.

Cryogenically Cooled

More expensive and more susceptible to damage from rugged use, these systems have the elements sealed inside a container that cools them to below 32 F (zero C). The advantage of such a system is the incredible resolution and sensitivity that result from cooling the elements. Cryogenically-cooled systems can "see" a difference as small as 0.2 F (0.1 C) from more than 1,000 ft (300 m) away, which is enough to tell if a person is holding a gun at that distance..

Continue……

Unlike traditional most night-vision equipment which uses image-enhancement technology, thermal imaging is great for detecting people or working in near-absolute darkness with little or no ambient lighting (i.e. stars, moonlight, etc, )

GENERATIONS

Generation 0

Generation 1

Generation 2

Generation 3

GENERATION 0

The first night vision devices, the M1 and M3 infrared night sighting devices, also known as the "sniperscope" or "snooperscope", were introduced by the US Army in World War II, and also used in the Korean War, to assist snipers. They were active devices, using a large infrared light source to illuminate targets. Their image intensifier tubes function using an anode and an S-1 photocathode, made primarily of silver, caesium and oxygen to accelerate the electrons

GENERATION 1

First generation passive devices, introduced during the Vietnam War were an adaptation of earlier active Gen 0 technology, and rely on ambient light instead of an infrared light source. Using an S-20 photocathode, their image intensifiers produce a light amplification of around 1000x, but are quite bulky and require moonlight to function properly.

Examples:

AN/PVS-2

GENERATION 2

Second generation devices featured an improved image-intensifier tube utilizing micro-channel plate (MCP) with an S-25 photocathode , resulting in a much brighter image, especially around edges of the lens. This leads to increased illumination in low ambient light environments, such as moonless nights. Light amplification was around 20000x Also improved were image resolution and reliability.

Examples:

AN/PVS-4

AN/PVS-5

SUPERGEN

GENERATION 3

Third generation night vision systems maintain the MCP from Gen II, but now use a photocathode made with gallium arsenide, which further improves image resolution. In addition, the MCP is coated with an ion barrier film for increased tube life. The light amplification is also improved, to around 30000-50000x

Examples:

AN/PVS-7

NVS-7

AN/PVS-14

NVS-14

XD-4, autogated or not

Advantage of Gen 3 over Gen 2

Gen 3 technology improves night operational effectiveness for military users of night vision goggles and other night vision devices. The filmless MCP provides a higher signal-to-noise ratio than Gen 2, resulting in better image quality (less scintillation) under low-light conditions. The gated power supply further improves image resolution under high light conditions, and the reduced halo minimizes interference from bright light sources. These improvements also substantially increase the detection range of the syste

Continued…… Courtesy of Matt Last GEN 2 GEN 3 % Improvement Photoresponse(ÂµA/Im) 1800 1800 - Signal-to-Noise Ratio 21.0 25 20% Higher Resolution(lp/mm) 64 64 - Halo(mm) 1.25 0.75 40% Smaller Reliability(hours) 10,000 10,000 -

Detection Range Gen 1 SuperGen 1 Gen 2 OMNI I and II Gen 2 OMNI III Gen 2 OMNI IV Gen 3 Detection Range (m) 170 270 240 290 360 430 % Improvement over Gen 1 0% 60% 40% 70% 110% 153%

How Far Can We See ??

There are many different variables that can effect the distance that you we see with a Night Vision device.

First which object we want to see.

The larger the object the easier it is too see.

Second. Another variable is lighting conditions. The more ambient light we have (starlight, moonlight, infrared light) the better and further we will be able to see .If it is cloudy and overcast then we typically state that we can tell the difference between a male and a female or a dog and a deer at about 75 to 100 yards.

If there is ambient light then we can see about 500 yards.

BLACK SPOTS ON THE SCREEN

As we look through a night vision device we may notice black spots on the screen. A NVD is similar to a television screen and attracts dust and dirt. Typically these spots can be cleaned.

These black spots will not affect the performance or reliability of the night vision device.

USAGE

Night vision devices were originally developed for military use, but have since spread into other areas, such as security and police work, rescue outfits and various amateur uses (for example animal watching or hunting).

Conclusion