NIGHT VISION TECHNOLOGY<br />Presented By-<br />PRATIK MONDAL<br />Roll No-2006 2004<br />Reg. No-387 of 2006-07<br />Department of Electronics & Communication Engineering<br />University Institute of Technology(Burdwan University)<br />
TABLE OF CONTENTS<br />Introduction.<br />Types of Night Vision<br />The eye & the night vision.<br />How night vision works<br />Night vision devices<br />Generations<br />Applications.<br />Conclusion.<br />Reference<br />
INTRODUCTION<br />Night vision technology, literally allows <br /> one to see in the dark .<br />It is originally developed for military use .<br />With the proper night-vision equipment, <br /> we can see a person standing over 200 <br /> yards (183 m) away on a moonless, cloudy <br />night. <br />
It is quite easy to see <br />everything during the day...<br />But at night, we can see very little.<br />Night device lets us to see again<br />
Types of Night Vision<br /><ul><li>Depending upon the way it is implemented it is broadly classified into two types</li></ul>(i) Biological Night vision<br />(ii) Technical Night vision<br /><ul><li>Be it biological or technical it based on two Night Vision Approaches-</li></ul>(i)SPECTRAL RANGE<br />(ii)INTENSITY RANGE<br />
THE EYE & NIGHT VISION<br /><ul><li>The interior portion of the eye is essentially a lens system ,purpose is to focus light into the retina. The retina contains receptor cells , rods & cones, which send signals to the brain.
The rods are responsible are responsible for vision under dim levels of illumination & the cones function at higher levels.
Human eye is perceive only the visible light portion of the electromagnetic spectrum ,so a low quality image is generated. To overcome these limitations “NIGHT VISION TECHNOLOGY” was developed. </li></li></ul><li>HOW NIGHT VISION WORKS<br /> Night vision can work in two very different ways , depending on the technology used. <br /><ul><li> Image intensifier
Thermal imaging </li></li></ul><li>IMAGE INTENSIFIER<br /><ul><li>This method of night vision amplifies the available light to achieve better vision .</li></ul>A conventional lens, captures ambient light. <br />The gathered light is sent to the image-intensifier tube. <br />The light energy causes electrons to be released from the cathode which are accelerated by an electric field to increase their speed.<br />These electrons enter holes in a micro channel plate and bounce off the internal specially-coated walls which generate more electrons .<br />
As electrons pass through the micro- channels, they cause thousands of other electrons to be released in each channel using a process called cascaded secondary emission. <br />Basically, the original electrons collide with the side of the channel, exciting atoms and causing other electrons to be released. <br />These new electrons also collide with other atoms, creating a chain reaction that results in thousands of electrons. <br />
At the end of the image-intensifier tube, the electrons hit a screen coated with phosphor.<br />The energy of the electrons causes the phosphors to reach an excited state and release photons. These phosphors create green image on the screen.<br />The green phosphor image is viewed through another lens, called the ocular lens.<br />LIMITATION<br /><ul><li>Not useful when there is essentially no light.
Possibility of damage when observing bright sources under low-light conditions. </li></li></ul><li>THERMAL IMAGING<br /><ul><li>This method do not require any ambient light at all.
principal -: All objects emit infrared energy as a function of their temperature.</li></ul>A special lens focuses the infrared light emitted by all of the objects in view. <br />The focused light is scanned by a phased array of infrared-detector elements. These create detailed temperature pattern called a thermogram.<br />The thermogram created by the detector elements is translated into electric impulses. <br />The impulses are sent to a circuit board with a dedicated chip that translates the information from the elements into data for the display. <br />
5. The signal-processing unit sends the information to the display, where it appears as various colors depending on the intensity of infrared emission.<br />
<ul><li>Thermal images are normally black and white in nature, where black objects are cold and white objects are hot.
Some thermal cameras show images in color. </li></ul> This false color distinguishes between objects at different temperatures. <br />
TYPES OF THERMAL IMAGING DETECTORS<br />Uncooled Infrared Detector:<br /><ul><li>Common type
The infrared-detector elements are contained in a unit that operates at room temperature.
Bulky in size.</li></ul>Cooled Infrared Detector:<br /><ul><li>Expensive and susceptible to damage.
infrared-detector elements are sealed inside a container that cools them to below 32 F .
cooled systems can see a distance more than 1,000 ft (300 m) away. </li></li></ul><li>NIGHT VISION DEVICES<br /><ul><li>Night vision devices are basically divided into three categories:
Scopes:They are monocular normally handheld or mounted on a weapon.
Goggles:They are binocular and worn on the head.
Cameras:Used for transmission or recording of images mostly if the location is fixed.</li></li></ul><li>PARTS OF NIGHT VISION DEVICE<br />Image intensifier tube<br />Phosphor screen<br />Objective lens<br />Infrared illuminator<br />
CONCLUSION<br /><ul><li>Today in the 21st century we have come a long way in the development of night vision technology, from the early 1940’s.
Night vision devices are basically designed for utmost defensive purposes but the application within the scientific or the civilian range is often prohibited by law.
In present scenario the applications of night vision technology is very essential to combat terrorism which is a major problem being faced by mankind.</li></li></ul><li>REFERENCES<br />http://www.google.co.in<br />http://www.photonis.com/nightvision/products/supergen/supergen_specifications<br />http://www.irinfo.org/articles/03_01_2007_grossman.html<br />http://www.weakipedia.org<br />