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1. INTRODUCTION
Night vision technology, by definition literally allows one to see in the dark. Originally developed for military use, it has provided the United states with strategic military advantage, the value of which can be measured in lives.
Federal and state agencies now routinely utilize the technology for site security, surveillance as well as search and rescue. Night vision equipment has evolved from bulky optical instruments in light weight goggles the advancement of image intensification technology.
Night vision has had many improvement thought-out the course of history. Its beginning data back to second world war when the Germans idealized a very effective way to easily use their sniper rifles during the night. This was later researched very deeply into because night vision proved to have a devastating advantage for those who used.
The proper night-vision equipment, you can see a person standing over 200 yards (183 m) away on a moonless, cloudy night.
NIGHT VISION APPROACHES
2.1 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.
2.2 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, the result of one or more differences in the morphology and anatomy of their eyes. These include having a larger eyeball, a larger lens, a larger optical aperture (the pupils may expand to the physical limit of the eyelids), more rods than cones (or rods exclusively) in the retina, a tapetumlucidum, and improved neurological filtering. 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
3.1 DEFINITION
A night vision device (NVD) is an optical installment 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 term usually refers to a complete unit, including an image intensifier tube, a protective and generally water-resistant housing, and some type of mounting system. Many NVDs also include sacrificial lenses, IR illuminators, and telescopic lenses. NVDs are mounted appropriately for their specific purpose, with more general-purpose devices having more mounting options. For instance, 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 hands free use with a harness or helmet attachment, either as a monocular device, or in aligned pairs for binocular "night vision goggles" which provide a degree of depth perception as do optical binoculars. The AN/PVS-14 may also be attached to a rifle using a Pica tinny rail, in front of an existing telescopic or red dot sight, or attached to a single-lens reflex camera. Other systems, such as the AN/PVS-22 or Universal Night Sight, are designed for a specific purpose, integrating an image intensifier into, for example, a telescopic sight, resulting in a smaller and lighter but less versatile system. Night vision devices were first used in World War II, and came into wide use during the Vietnam War The technology has evolved greatly since their introduction, leading to several "generations" of night vision equipment with performance increasing and price decreasing. Division of Computer Engineering.
3.3 Working of night vision device :
Night Vision technology consists of two major types: image intensification (light amplification) and thermal imaging (infrared).
3.3.1 Image Intensification (light amplification) :
Most consumer night vision products are light amplifying devices. Light amplification is less expensive than thermal, however, higher-end and more effective night vision tubes can become more expensive. 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. Like the one your see to your right . But that's where the similarities end.
ELECTRONS PHOTONS
3.3.2 Thermal Imaging :
In order to understand thermal imaging, it is important to understand something about light. 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.
Infrared
Ultraviolet
Spectrum of light
Image enhancement –
This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.
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.
In this article, you will learn about the two major night vision technology. We’ll also discuss the various type of night vision equipment and applications. But first, let’s talk about infrared light.