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NIGHTVISION TECHNOLOGY

NIGHTVISION TECHNOLOGY . SUBMITTED BY Srabani Kanungo 0301223362 (ENTC). INTRODUCTION.

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NIGHTVISION TECHNOLOGY

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  1. NIGHTVISION TECHNOLOGY SUBMITTED BY SrabaniKanungo 0301223362 (ENTC)

  2. INTRODUCTION • Night vision technology enables you to see objects clearly at night at distances up to several hundred yards in the absence of any artificial light. People, buildings, vehicles & details of the landscape viewed through a modern night vision system appear almost as if illuminated while the same objects viewed with a naked eye would appear only as indistinct shadow .Depending upon the way it is implemented it is broadly classified into two types • (i) Biological Night vision (ii)Technical Night vision

  3. TYPES OF NIGHTVISION • Depending upon the way it is implemented it is broadly classified into two types • Biological Night vision • Technical Night vision

  4. BIOLOGICAL NIGHT VISION • In biological night vision, molecules of rhodopsin in the rods of The eye undergo a change in shape as light is absorbed by them. The peakrhodopsin build-up time for optimal night vision in humans is 30 minutes.Rhodopsin in the human rods is insensitive to the longer red wavelengths of light, so many people use red light to preserve night vision as it will not deplete the eye's rhodopsin stores in the rods and instead is viewed by the cones. Some animals,such as cats, dogs, and deer, have a structure called the tapetuminthe back of the eye that reflects light for even better night vision than humans, in which only 10% of the light that enters the eye falls on photosensitive parts of the retina.

  5. TECHNICAL NIGHT VISION • BASIC PRINCIPLE • It based upon the principles of photo electric effect • EQUATIONS: E=hf , E=W + EK • Where • E=Energy of the radiation • W=Work function • EK=Kinetic energy of the electrons • h=Plank’s constant • f=Frequency of the radiation

  6. RANGES OF NIGHT VISION • ENHANCED SPECTRAL RANGE • Enhanced spectral range techniques make the viewer sensitive to types of light that would be invisible to a humanobserver. Human visionis confined to a small portion of the electromagnetic spectrum called visible range. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or UV radiation) • ENHANCED INTENSITY RANGE • Enhanced 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 condition. Some animals have evolved better night vision through the use of a larger optical aperture, improved retina composition that can detect weaker light over a larger spectral range, more photo efficient optics in the eye, and improved neurological filtering which is more tolerant of noise. 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.

  7. IMAGE ENHANCEMENT TECHNIQUE • Image-enhancement technology is what most people think of when you talk about night vision. In fact, image-enhancement systems are normally called night-vision devices (NVDs). NVDs rely on a special tube, called an image-intensifier tube, to collect and amplify infrared and visible light. • The image-intensifier tube changes photons to electrons and back again.

  8. how image enhancement works: • A conventional lens, called the objective lens, captures ambient light and some near-infrared light. • The gathered light is sent to the image-intensifier tube. In most NVDs, the power supply for the image-intensifier tube receives power from two N-Cell or two "AA" batteries. The tube outputs a high voltage, about 5,000 volts, to the image-tube components. • The image-intensifier tube has a photocathode, which is used to convert the photons of light energy into electrons. • As the electrons pass through the tube, similar electrons are released from atoms in the tube, multiplying the original number of electrons by a factor of thousands through the use of a micro channel plate (MCP) in the tube. An MCP is a tiny glass disc that has millions of microscopic holes (micro channels) in it, made using fiber-optic technology. The MCP is contained in a vacuum and has metal electrodes on either side of the disc. Each channel is about 45 times longer than it is wide, and it works as an electron multiplier.

  9. At the end of the image-intensifier tube, the electrons hit a screen coated with phosphors. These electrons maintain their position in relation to the channel they passed through, which provides a perfect image since the electrons stay in the same alignment as the original photons. The energy of the electrons causes the phosphors to reach an excited state and release photons. These phosphors create the green image on the screen that has come to characterize night vision. • The green phosphor image is viewed through another lens, called the ocular lens, which allows you to magnify and focus the image. The NVD may be connected to an electronic display, such as a • monitor, or the image may be viewed directly through the ocular lens.

  10. DIFFERENT GENERATIONS OF INTENSIFIER TUBE • Generation 0 • Generation 0 devices took a lot of power to use, for both the tube and the IR illuminator, had a very distorted picture due to a cone-shaped electrode design, and a short tube life due to the high electrical voltage. Generation 0 featured a photocathode made of a mixture of silver, caesium, and oxygen called S-1 which provided approximately 60 mA/lm sensitivity to light. • Generation 1 • Generation 1 devices are also called "Starlight scopes", and were a tremendous improvement upon generation 0. They are much more power efficient, amplify light better, and produced a superior image. Generation 1 also used a different photocathode, S-20, which provided about three times the photo sensitivity of Generation 0. • Generation 1 remains one of the most popular types of night vision today. Despite its poor performance, its low cost entices people who are looking to pick up night vision as a toy.

  11. Generation 2 • Generation 2 was a major technological breakthrough. Although the photocathode material, S-25, wasn't much of an improvement over Generation 1's S-20, generation 2 devices introduced the microchannel plate .The microchannel plate consists of a bundle of thousands of tiny glass fibres fused together in parallel, sliced transversely, and polished on both faces. Electrons impinging on one side of the plate tend to travel along the fibres, perpendicular to the plate's faces, thus preserving a coherent image. As good as Generation 2 was, though, it was soon to be overshadowed by a new photocathode material. • Generation 3 • Generation 3 is the latest "generation" and is in use by the U.S. military and others. It is essentially generation 2 technology with a new photocathode material—gallium arsenide and a better MCP. Gallium arsenide provides far better response to near-infrared light. This is very important as the majority of starlight is in the IR spectrum. However, this comes at a cost of decreased sensitivity to blue light.

  12. Later Generations • There are newer night vision systems available. Generation 3 Ultra and Generation 4 tubes exist. Most civilian equipment remains based on Generation 3 equipment and lower, however. Generation 3 Ultra and 4 still use MCP technology, but are designed to offer greater range, and higher resolution. • 1. 2. . 3. • It is quite easy to see everything during the day... • ...but at night, you can see very little. • 3. View through Night vision devices.

  13. IR VISION • This is another way of achiveing night vision by using thermal imaging. • BASIC PRINCIPLE • It based on the two principle. • (i)PLANK’S BLACKBODY RADIATION • Every object above zero degree kelvin radiates electromagnetic energy. • (ii)WIEN’S DISPLACEMENT LAW • Wave length of the radiation decreases as temperature increases and vice versa. • They are simple devices that do not produce a net amplification of light, but rather allow a user to see near-infrared light. Along with beam filters, this allowed snipers to illuminate their target without their target being aware of it.

  14. THERMAL IMAGING • (i)A special lens focuses the infrared light emitted by all of the objects in view. • (ii)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 • (iii)The thermogram created by the detector elements is translated into electric impulses. • (iv)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. • (V)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.

  15. TYPES OF IR DEVICES • UNCOOLED -Most common device, operate in room temperature detector is made of In-Sb.It has a built in battery • CRYOGENICALY COOLED -Most expensive , made of In-Ga-As ,liquid nitrogen is used to cool the system below 00c .its working range is from -200c to 20000c

  16. APPLICATION • ELECTRICAL INTERFACES • In the electrical distribution station,one portion of it is hot due to short circuit or some problem. But it will not visible to the naked eye. • SECURITY SYSTEM • This another application of IR imaging. The radiation pattern of every human beingis unique. So by taking this pattern we can store it in some database & can use for future reference. • TO DETECT THE FLAW IN ELECTRONICS CHIP • Due to some defect in the circuit the portion of this circuit is more hot As compare to the other portion of the circuit which will not visible to the naked eye. But by scan it with the help of a IR device we can detect the flaw. Its one of the popular application of IR imaging.

  17. APPLICATION • MECHANICAL APPLICATION • Its used in the steel industry to monitor the blast furnace. We can detect the hot portion of the furnace and take necessary precaution. • CIVIL APPLICATION • There is always a difference of temperature between outside environment & the innerside of the building. If there is any crack then there will be a temperature flow within the crack. Hence this part of the building is more hot as compare to the other & hence radiate more. In otherwords the wet portion ,which is portion of crack will radiate more & we can take necessary precaution . • The similar kind of incident happened during the Bhopal gas tragedy. In the above image there is a fracture which is not visible to the ordinary Eye

  18. CONCLUSION Night vision is one of the emerging technology which is used in Different fields like in industry, by the military persons. So more Sophisticated technology needs to be developed to implement night vision in a better way.

  19. Thank You...

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