1. DIGITAL IMAGE PROCESSING“HOW NIGHT VISION WORKS”ByS.SREEVIDYA-08F41A04B4BRANCH: ECESiddu.firstname.lastname@example.orgN.SUDHA RANI-08F41A0482BRANCH: ECESudharani.email@example.comKUPPAM ENGINEERING COLLEGEKES Nagar, Kuppam - 517 425,Chittoor Dist, A.P.,
2. ABSTRACTNight Vision scopes and binocularsare electro-optical devices thatintensify (or amplify) existing lightinstead of relying on a light sourceof their own. The devices aresensitive to a broad spectrum oflight, from visible through infrared.An accessory illuminator canincrease the lightavailable at the infrared end of thespectrum by casting a beam of lightthat is not visible to the human eye.Our paper is an image processapplication for night visiontechnology, which can be often usedby the military and law enforcementagencies, but are available tocivilian users . In our work, nightvision googles capture the imageeven in the dark in the infraredregion.An infrared night vision systemsenses heat radiated by things andproduces a video picture of the heatscene. The gadget that senses theheat is a photocathode, similar tothe one in a video camera, except itis sensitive to infrared radiationinstead of visible light. ability toimprove poor night vision.There are two methods of operatingnight vision systems, being either ina passive mode or an active mode.Passive systems amplify theexisting environmental ambientlighting, while active systems relyon an infrared light source toprovide sufficient illumination.Active systems are often used todayon many consumer devices such ashome video cameras.Night vision works on twotechniques: image enhancement,thermal imaging.Applications ofthis technology areSurveillance,Security,Wildlife observation,lawenforcement.
3. How Night Vision WorksIntroduction to How NightVision WorksThe first thing you probably thinkof when you see the words nightvision is a spy or action movieyouve seen, in which someonestraps on a pair of night-visiongoggles to find someone else in adark building on a moonless night.And you may have wondered "Dothose things really work? Can youactually see in the dark?"Night Vision Image GalleryGyro-stabilized day/night binoculars.The answer is most definitely yes.With the proper night-visionequipment, you can see a personstanding over 200 yards (183 m)away on a moonless, cloudy night!
4. Night vision can work in two verydifferent ways, depending on thetechnology used.Infrared Light:In order to understand night vision,it is important to understandsomething about light. The amountof energy in a light wave is relatedto its wavelength: Shorterwavelengths have higher energy. Ofvisible light, violet has the mostenergy, and red has the least. Justnext to the visible light spectrum isthe infrared spectrum.Infrared light is a small part of the light spectrum.Infrared light can be split into threecategories:• Near-infrared (near-IR) -Closest to visible light, near-IR has wavelengths thatrange from 0.7 to 1.3microns, or 700 billionths to1,300 billionths of a meter.• Mid-infrared (mid-IR) -Mid-IR has wavelengthsranging from 1.3 to 3microns. Both near-IR andmid-IR are used by a varietyof electronic devices,including remote controls.• Thermal-infrared (thermal-IR) - Occupying the largestpart of the infraredspectrum, thermal-IR haswavelengths ranging from 3microns to over 30 microns.The key difference betweenthermal-IR and the other two is thatthermal-IR is emitted by an objectinstead of reflected off it. Infraredlight is emitted by an object becauseof what is happening at the atomiclevel.Basic Technologies:Night vision work in two verydifferent ways, depending on thetechnology usedImage enhancement - Thisworks by collecting the tinyamounts of light, including thelower portion of the infrared lightspectrum, that are present but may
5. be imperceptible to our eyes, easilyobserve the image.Thermal imaging - Thistechnology operates bycapturing the upper portion ofthe infrared light spectrum,which is emitted as heat byobjects instead of simplyreflected as light. Hotter objects,such as warm bodies, emit moreof this light than cooler objectslike trees or buildings.INFRA-REDILUMINATORSAll Starlight scopes need somelight to amplify. This means that ifyou were in complete darkness youcould not see. Due to this we have abuilt in infra-red illuminator (IRI)on all of our scopes. Basically whatan IRI does is throw out a beam ofinfra-red light that is near invisibleto the naked eye but your NVD cansee it. This allows you to use yourscope even in total darkness. TheIRI works like a flashlight and thedistance you can see with it will belimited. We do use the mostpowerful eye-safe illuminator on themarket. This allows our IRI toextend out to 100 yards However,because of the power at a shortdistance the IRI may cover only 40-60% of the viewing area.When you look through a nightvision device you may notice blackspots on the screen. A NVD issimilar to a television screen andattracts dust and dirt. Typicallythese spots can be cleaned.However, this may also be a spot inthe tube itself. This is normal. Mosttubes will have some spots in them.These black spots will not affect theperformance or reliability of thenight vision device.Night visiondevices gather existing ambient1. Front Lens4. High Voltage PowerSupply2. Photocathode 5. Phosphorus Screen3.Micro-channelplate6. Eyepiece
6. light (starlight, moonlight orinfrared light) through the frontlens. This light, which is made up ofphotons goes into a photocathodetube that changes the photons toelectrons. The electrons are thenamplified to a much greater numberthrough an electrical and chemicalprocess. The electrons are thenhurled against a phosphorus screenthat changes the amplified electronsback into visible light that you seethrough the eyepiece. The imagewill now be a clear green-huedamplified re-creation of the sceneyou were observing.Recent Development in theField of Night VisionNight Visions mission is to: Conduct Research andDevelopment to Provide USLand Forces with AdvancedSensor Technology toDominate the 21st CenturyDigital Battlefield; Acquire and Target EnemyForces in BattlefieldEnvironments; Detect and NeutralizeMines, Minefields, andUnexploded Ordnance;Develop HumanitarianDemining Technology; Deny Enemy Surveillance &Acquisition through Electro-Optic, Camouflage,Concealment and DeceptionTechniques; Provide for Night Drivingand Pilotage; and Protect Forward Troops,Fixed Installations and RearEchelons from EnemyIntrusion.Working of ImageEnhancement:Image-enhancement technology iswhat most people think of when youtalk about night vision. In fact,image-enhancement systems arenormally called night-vision devices(NVDs). NVDs rely on a specialtube, called an image-intensifiertube, to collect and amplify infraredand visible light.Heres how image enhancementworks:
7. 1. A conventional lens, calledthe objective lens, capturesambient light and some near-infrared light.2. The gathered light is sent tothe image-intensifier tube. Inmost NVDs, the power supplyfor the image-intensifier tubereceives3. power from two N-Cell ortwo "AA" batteries. The tubeoutputs a high voltage, about5,000 volts, to the image-tubecomponents.4. The image-intensifier tubehas a photocathode, which isused to convert the photons oflight energy into electrons.5. As the electrons passthrough the tube, similar electronsare released from atoms in the tube,multiplying the original number ofelectrons by a factor of thousandsthrough the use of a microchannelplate (MCP) in the tube. An MCPis a tiny glass disc that has millionsof microscopic holes(microchannels) in it, made usingfiber-optic technology. The MCP iscontained in a vacuum and hasmetal electrodes on either side ofthe disc. When the electrons fromthe photo cathode hit the firstelectrode of the MCP, they areaccelerated into the glassmicrochannels by the 5,000-Vbursts being sent between theelectrode pair. As electrons passthrough the microchannels, theycause thousands of other electronsto be released in each channelusing a process called cascadedsecondary emission. Basically, theoriginal electrons collide with theside of the channel, exciting atomsand causing other electrons to bereleased. These new electrons alsocollide with other atoms, creating achain reaction that results inthousands of electrons leaving thechannel where only a few entered.An interesting fact is that themicrochannels in the MCP are
8. created at a slight angle (about a 5-degree to 8-degree bias) toencourage electron collisions andreduce both ion and direct-lightfeedback from the phosphors onthe output side.At the end of the image-intensifiertube, the electrons hit a screencoated with phosphors. Theseelectrons maintain their position inrelation to the channel they passedthrough, which provides a perfectimage since the electrons stay in thesame alignment as the originalphotons. The energy of the electronscauses the phosphors to reach anexcited state and release photons.These phosphors create the greenimage on the screen that has come tocharacterize night vision.The green phosphor image isviewed through another lens, calledthe ocular lens, which allows you tomagnify and focus the image. TheNVD may be connected to anelectronic display, such as amonitor, or the image may beviewed directly through the ocularlens.Thermal Imaging Process:Image of a small dog taken in mid-infrared ("thermal") light (falsecolor)Thermal imaging, also called asthermo graphic or thermal video, isa type of infrared imaging. Thermographic cameras detect radiation inthe infrared range of theelectromagnetic spectrum (roughly900–14,000 nanometers or 0.9–14µm) and produce images of thatradiation. Since infrared radiation isemitted by all objects based on theirtemperatures, according to the blackbody radiation law, thermographmakes it possible to "see" onesenvironment with or without visibleillumination. The amount ofradiation emitted by an objectincreases with temperature,therefore thermograph allows one tosee variations in temperature (hencethe name). When viewed bythermographic camera, warmobjects stand out well against cooler
9. backgrounds; humans and otherwarm-blooded animals becomeeasily visible against theenvironment, day or night. As aresult, thermographys extensive usecan historically be ascribed to themilitary and security services.Thermal imaging photographyfinds many other uses. For example,firefighters use it to see throughsmoke, find persons, and localizethe base of a fire. With thermalimaging, power lines maintenancetechnicians locate overheatingjoints and parts, a telltale sign oftheir failure, to eliminate potentialhazards. Where thermal insulationbecomes faulty,building construction technicianscan see heat leaks to improve theefficiencies of cooling or heatingair-conditioning. Thermal imagingcameras are also installed in someluxury cars to aid the driver, thefirst being the 2000 CadillacDeVille. Some physiologicalactivities, particularly responses, inhuman beings and other warm-blooded animals can also bemonitored with thermographicimaging. The appearance andoperation of a modern thermographic camera is often similar to acamcorder. Enabling the user to seein the infrared spectrum is afunction so useful that ability torecord their output is often optional.A recording module is therefore notalways built-in.Instead of CCD sensors, mostthermal imaging cameras useCMOS Focal Plane Array (FPA).The most common types are Insb,InGaAs, QWIP FPA. The newesttechnologies are using low cost anduncooled micro bolometers FPAsensors. Their resolution isconsiderably lower than of opticalcameras, mostly 160x120 or320x240 pixels, up to 640x512 forthe most expensive models.Thermographic cameras are muchmore expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted. Older bolometer or moresensitive models as InSB requirecryogenic cooling, usually by aminiature Stirling cycle refrigeratoror liquid nitrogen.Generations:
10. NVDs have been around for morethan 40 years. They are categorizedby generation. Each substantialchange in NVD technologyestablishes a new generation.Generation 0 - The originalnight-vision system created bythe United States Army andused in World War II and theKorean War, these NVDs useactive infrared.Generation 1 - The nextgeneration of NVDs moved awayfrom active infrared, using passiveinfrared instead.This also meansthat they do not work very well oncloudy or moonless nights.Generation-1 NVDs use the sameimage-intensifier tube technologyas Generation 0, with both cathodeand anode, so image distortion andshort tube life are still a problem.Generation 2 - Majorimprovements in image-intensifiertubes resulted in Generation-2NVDs. They offer improvedresolution and performance overGeneration-1 devices, and areconsiderably more reliable. Thebiggest gain in Generation 2 is theability to see in extremely low lightconditions, such as a moonlessnight. This increased sensitivity isdue to the addition ofthe microchannel plate to theimage-intensifier tube. Since theMCP actually increases the numberof electrons instead of justaccelerating the original ones, theimages are significantly lessdistorted and brighter than earlier-generation NVDs.Generation 3 - While there areno substantial changes in theunderlying technology fromGeneration 2, these NVDs haveeven better resolution andsensitivity. This is because thephoto cathode is made usinggallium arsenide, which is veryefficient at converting photons toelectrons. Additionally, the MCP iscoated with an ion barrier, whichdramatically increases the life of thetube.Generation 4 - What isgenerally known as Generation4 or "filmless and gated"technology shows significantoverall improvement in bothlow- and high-level lightenvironments.
11. The removal of the ion barrierfrom the MCP that was added inGeneration 3 technology reducesthe background noise andthereby enhances the signal tonoise ratio. Removing the ionfilm actually allows moreelectrons to reach theamplification stage so that theimages are significantly lessdistorted and brighter.consider the ubiquitous moviescene where an agent using nightvision goggles is “sightless”when someone turns on a lightnearby. With the new, gatedpower feature, the change inlighting wouldn’t have the sameimpact; the improved NVDwould respond immediately to thelighting change.Many of the so-called "bargain"night-vision scopes use Generation-0or Generation-1 technology, and maybe disappointing if you expect thesensitivity of the devices used byprofessionals. Generation-2,Generation-3 and Generation 4NVDs are typically expensive topurchase, but they will last ifproperly cared for. Also, any NVDcan benefit from the use of an IRIlluminator in very dark areas wherethere is almost no ambient light tocollect.A cool thing to note is that everysingle image-intensifier tube is putthrough rigorous tests to see if itmeets the requirements set forth bythe military. Tubes that do areclassified as MILSPEC. Tubes thatfail to meet military requirements ineven a single category are classifiedas COMSPEC.Night Vision Equipment :Night-vision equipment can be splitinto three broad categories:Scopes - Normally handheld ormounted on a weapon, scopesare monocular (one eye-piece).Since scopes are handheld, notworn like goggles, they are goodfor when you want to get abetter look at a specific objectand then return to normalviewing conditions.
12. DARK INVADER Multi-purpose PocketscopeGoggles - While goggles canbe handheld, they are most oftenworn on the head. Goggles arebinocular (two eye-pieces) andmay have a single lens or stereolens, depending on the model.Goggles are excellent forconstant viewing, such asmoving around in a darkbuilding.Cameras - Cameras withnight-vision technology cansend the image to a monitor fordisplay or to a VCR forrecording. When night-visioncapability is desired in apermanent location, such as on abuilding or as part of theequipment in a helicopter,cameras are used. Many of thenewer camcorders have nightvision built right in.Applications:Common applications for nightvision include:• Military• Law enforcement• Hunting• Wildlife observation• Surveillance• Security• Navigation• Hidden-object detection• EntertainmentThe original purpose of night visionwas to locate enemy targets at night.It is still used extensively by themilitary for that purpose, as well asfor navigation, surveillance andtargeting. Police and security oftenuse both thermal-imaging andimage-enhancement technology,particularly for surveillance.Hunters and nature enthusiasts use
13. NVDs to maneuver through thewoods at night.Detectives and private investigatorsuse night vision to watch peoplethey are assigned to track. Manybusinesses have permanently-mounted cameras equipped withnight vision to monitor thesurroundings.A really amazing ability of thermalimaging is that it reveals whether anarea has been disturbed -- it canshow that the ground has been dugup to bury something, even if thereis no obvious sign to the naked eye.Law enforcement has used this todiscover items that have beenhidden by criminals, includingmoney, drugs and bodies. Also,recent changes to areas such aswalls can be seen using thermalimaging, which has providedimportant clues in several cases.Many people are beginning todiscover the unique world that canbe found after darkness falls.Night Vision System forCars:At the International Motor Show(IAA) in Frankfurt, Siemens hasintroduced a night vision systemthat works with infrared technology.With this innovation, Siemens hasalso become the first automotiveindustry supplier to create aprototype of an electronicpedestrian marking system. Onequarter of all serious trafficaccidents take place in the eveningor at night. And about one third ofall traffic fatalities are the result ofaccidents during these hours.That’s why Siemens VDOAutomotive has developed aninfrared system that’s up to seriesproduction standards. Night Visionmakes a vehicle’s darkenedsurroundings visible out to adistance of 150 meters. NightVision generates an electronicallyprocessed video image that can bedisplayed in real time either in thehead-up display or on a TFT
14. monitor in the instrument panel.Depending on the automotiveindustry’s design requirements,Night Vision works with twodifferent systems. With the near-infrared system, two barelynoticeable infrared emitters areintegrated into the headlights. Theinfrared light they produce iscaptured by a small camerapositioned close to the rear-viewmirror. The second system, asolution in the long-wave spectralrange, a high-resolution infraredcamera is installed behind theradiator grille. Using a wavelengthof six to 12 micrometers, it detectsthe infrared heat radiation from thevehicle’s surroundings, which isdisplayed as a negative image:Objects that are cold — becausethey are inanimate — appeardarkened, and living things aredisplayed as brightobjects.The pedestrian marking in the videoimage has been realized by SiemensVDO as a prototype with imageprocessing electronics. Thisanalyzes all the image dataaccording to temperaturedifferences and typical shapes andmarks pedestrians on the monitorwith a warning. It will be some timebefore these special features will beready for market launch.The advanced development phasefor an exclusively video-supportedNight Vision system has beencompleted, however. Production aspart of a network of driverassistance systems could belaunched in 2008. In addition to theelectronic recognition andevaluation of a vehicle’ssurroundings, Siemens VDO seescomfortable interaction betweendriver and system as the mostimportant development priority.CONCLUSION: It’s acritical study, which plays a vitalrole in modern world as it isinvolved with advanced use ofscience and technology. Theadvances in technology havecreated tremendous opportunitiesfor Vision System and ImageProcessing.The technology hasevolved greatly since theirintroduction, leading to several
15. "generations" of night visionequipment with performanceincreasing and pricedecreasing.From the abovediscussion we can conclude that thisfield has relatively more advantagesthan disadvantages and hence isvery useful in varied branches.REFERENCES:http://medind.nic.in/iab/t06/i1/iabt06i1p11.pdfhttp://blogs.ibibo.com/eminem/Night-Vision-Technology.htmlhttp://electronics.howstuffworks.com/nightvision5.htm