NIGHT VISION

ABSTRACT

Submitted by

Sadekur Rahaman ECE-29/08

Debayan Kabiraj ECE-37/08

Night vision technology, by definition, literally allows one to see in the dark, it helps humans see in what we call the dark. Humans see in only a small part of the light spectrum. Light is made of waves of energy and the longer the wave is, the less energy it has. The shorter a wave is, the more energy it contains which means that the visible light we see has a range of energy levels. Red is the lowest. Violet has the highest energy. The color spectrum increases in energy as you go from red, orange, yellow, green, blue, indigo, and the highest violet. Below the visible red waves, we can see are even lower energy waves called infrared. We can also call these heat waves. The infrared part of the light spectrum can be divided into three types. Near infrared is closest to visible red light. Mid infrared waves are longer and farther away from visible red light. Thermal infrared has longer wavelengths still. Violet is the highest visible wavelength, which humans can see. Above the violet colored waves, we see in the visible light spectrum, are the ultra violet waves, which has higher energy waves than

Visible violet light.
Night vision devices can help us to see a great distance away on a cloudy night when there is no moon light and it works in two ways.
One way uses light that that we cannot see toward the infrared end of the light spectrum. This light is amplified to the point where we can see images.
A lens focuses visible and infrared light into a special electronic tube that intensifies a dim image into a strong one. The few photons that exist in the dim light are converted to electrons. The electrons, pushed by a strong voltage within the tube, collide with the sides of the slightly bent tube to create thousands of electrons. Electrons hitting other electrons in the micro channels of the vacuum tube generate thousands more electrons than there were to start with. There is a screen covered with phosphors at the end of the tube. When the electrons hit the phosphors they become excited. A greenish light is given off in the image of what there is

to be seen.

Another way night vision is achieved is by using the heat objects give off. This is how thermal imaging works. The light given off by warm objects is focused by a specially designed lens. This infrared light hits an electronic detector device, which creates a detailed pattern of the differences in temperature. This pattern is called a thermogram. The information held in the thermogram is transformed into electrical impulses. A little computer creates usable data from the electrical impulses and the data is processed more and sent to a display where it is seen as various colors, depending on how much infrared light an object was giving off. There must be a temperature difference between objects and their surroundings to detect images. This image can be viewed through a scope like in a pair of binoculars or on a monitor screen.

NVD 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:

Generations	Invention Time	Uses
Generation 0	The earliest (1950's)	Created by US Army Uses active infrared.
Generation 1	1960's (Vietnam Era)	Uses passive infrared Uses ambient light provided by the moon and the stars.
Generation 2	late 1970s and early 1980s	Offer improved resolution and performance over Generation-1 devices.
Generation 3	1990	Uses the gallium arsenide (GaAs) photocathode and the ion-barrier Film on the MCP.
Generation 4	2000	Known as filmless and gated technology Shows significant improvement in both high- and low-level light environments.

The original purpose of night vision was to locate enemy targets at night. It is still used extensively by the military for that purpose, as well as for navigation, surveillance and targeting. Police and security often use both thermal-imaging and image-enhancement technology, particularly for surveillance. Hunters and nature enthusiasts use NVDs to maneuver through the woods at night. Detectives and private investigators use night vision to watch people they are assigned to track. Many businesses have permanently-mounted cameras equipped with night vision to monitor the surroundings.