sight sight sight optical device allows user look partially reflecting glass element illuminated projection aiming point image superimposed field view sights work simple optical principle focus lens curved mirror illuminated look like sitting viewer infinity sights employ sort allow viewer infinity image field view time bouncing image created lens glass plate clear curved glass images viewer looks infinity stays alignment device sight attached regardless viewer eye position removing sighting errors found simple sighting devices invention sights come gun sights kinds weapons fighter aircraft limited capacity world war widely world war base component types modern head displays types usually large weapons anti aircraft gun sights anti tank gun sights role operator engage fast moving targets wide field view sight supplied sufficient electrical power function limited use sight small arms world war came widespread use late 1970s invention red dot sight red light led making sight extremely long illumination run time sights civilian applications sights surveying equipment optical pointing aids camera design sights work lens image forming curved mirror reflective image focus creating optical produces virtual image image reflected form angled beam partially curved mirror observer looking beam mirror image focus superimposed sight field view focus ranges infinity optical produces image light light nearly parallel light making image theoretically perfectly parallel axis device gun barrel aligned infinity image seen eye position cylindrical volume light created sight optical window means targets closer infinity sighting edge optical window relation target observer sighting parallel light bundle edge eye movement perpendicular device optical axis image exact relationship eye position cylindrical column light created common type applications aircraft gun sights uses lens beam type tends requires optical components lens beam glass plate situated optical path making lighting difficult usually needing additional electric illumination lenses etc compact type replaces lens beam configuration half curved mirror set angle performs tasks focusing combining image offset type seen red dot type small arms possible place viewer curved mirror mirror focus close eye focus curved mirror presents viewer image infinity type invented dutch optical engineer originally camera featured folding reflecting sight assembly viewing portion sight use optical elements simply projected bounced beam curved mirror right users eye gives defining characteristics needing considerable experience skill use opposed simple mechanical sights iron sights sight field view eye relief problems sights based optical depending design constraints field view user naked eye field view non focusing nature means don optical eye relief sights combined usually placing directly sight view projected creating sight introduces problems narrow field view limited eye relief primary sight need way function illuminated ambient light hard use low light situations sights electrical illumination stop functioning altogether system fails history idea sight originated irish optical designer maker patent conceived gun sight large small ordnance better alternative difficult use iron sight avoiding sight limited field view greater apparent target speed errors danger keeping eye eye stop scientific transactions described invention possible conceive arrangement fine beam light like search light projected gun direction axis adjusted correspond line fire beam light object shot hit arrangement course equally obvious reasons beam light necessary qualifications purposes sight forms subject paper similar result projecting actual spot light image object projecting called optical language virtual image noted soon invention sight good alternative iron sights uses surveying measuring equipment sight german fighter aircraft widely adopted kinds fighter bomber aircraft 1930s world war sight types weapons aircraft including anti aircraft guns naval guns anti tank weapons weapon user needed simplicity quick target acquisition nature sight development 1930s sight referred applications sight weapon sights sights invented improved gun sight invention adapted types weapons different types guns sights considered improvement simple iron sights sights composed spaced metal aiming points aligned iron sights considerable experience skill user hold proper eye position simultaneously focus rear sight sight target different distances align planes focus achieve hit sight single free virtual image focus target removes aiming problem helping poor average expert shooters alike image produced sight truly free infinity sight error circle equal diameter target finite distance depending eye position sight target aiming error larger targets distance given non quick target acquisitions nature sight aiming error considered trivial small arms aimed close targets compensated keeping middle optical window sighting optical axis manufacturers small arms sights models optical set finite distance gives sight eye movement size optical window close range minimal size set distance desired target range yards compared standard sights sight held distance eye require designed eye relief angle image target eyes open brain tend automatically illuminated image coming dominant eye eye view giving shooter normal depth perception field view sights dependent eye relief theoretically placed convenient mounting position weapon aircraft earliest record sight fighter aircraft optical firm berlin working patents developed versions came known sight degree angle glass beam electrical illumination aim plane machine guns version operational trials fighter fighter interest sight world war sights general widely adopted fighter bomber aircraft 1930s french major sights aiming fighter aircraft aircraft defensive guns sights aircraft gun sights advantages pilot gunner need position head align sight line precisely point mechanical sights head position limited determined diameter lens sight interfere overall view particularly light turned eyes simultaneously sighting optical nature sight meant possible feed information field view modifications aiming point determined input saw development british sights adjusted aircraft speed rate turn enabling display lead adjusted sighting actual weapon allowing lead target turn proper effective strike sight designs advanced world war giving pilot information eventually evolved head display illuminated eventually replaced video screen focus gave sighting point information lead finding computer radar aircraft artificial horizon compass altitude visual tracking targets transition instrument visual methods landings firearms idea sight invention soon world war models appeared rifles including shotgun sight curved semi reflective mirror reflect ambient lit electric battery powered illuminated later types included thompson sight beam type sights ambient light green sight red plastic rod light pipe produced red aiming spot mid- late 1970s saw introduction usually referred red dot sights type gives user simple bright red dot aiming point typical configuration sight compact curved mirror design red light led focus led innovation greatly improves reliability general sight need optical elements focus light mirror use coating reflect red spectrum passing light led solid state little power allowing battery powered sights run hundreds tens thousands hours sights military firearms usually referred sights took long time adopted noted far use sight military widely introduce sights early 2000s red dot sight designated close combat types illumination pattern options available common light sources sights include battery powered lights fiber light collectors sights specifically designed visible viewed night vision devices color sight red amber visibility backgrounds sights use triangular pattern instead aid precision aiming range provide patterns sights use dot invariably measured minutes angle convenient measure shooters english units approximately inch distance yards makes unit use dot small obscure targets large quickly acquire proper sight picture types action shooting larger dot preferred dots rings combined horizontal vertical lines provide level reference sights active passive adjustments help shooter adapt different lighting conditions dim help prevent loss night vision low light conditions brighter display clearly sunlight configurations modern optical sights designed firearms uses fall housing configurations open tube sights look similar standard sights cylindrical tube containing tube sights offer option filters reducing filters reducing protective flip lens covers open sights known mini sights mini red dots advantage fact sight optical element optical window doesn need housing configuration consists base necessary reflective surface mounted diminished profile open sights usually accommodate filters options typically supported tube designs uses sights years nautical navigation devices surveying equipment type sights early large format cameras point shoot type cameras simple cameras sights astronomical help aim desired object commercial models invented amateur late 1970s available companies sights entertainment industry productions live theater follow spot sights adapted use purpose built spot dot allow spotlight operator aim light turning similar types sights called eye simply optical focusing optical window viewer sees image eyes open looks sight eye open moving head alternately sight target eye partially sight target time illuminated electric passive ambient light source examples commercially available ambient lit sights sights advantage requiring illumination level high contrast black background reason eye practical use small arms low power consumption illumination sources commonplace weapon sights similar layout sights use projected system instead representative recorded dimensional space film time manufacture image optical viewing window recorded illuminated laser built sight sight adjusted range simply optical window
Reflector sight