HistoryBehindDigitalProjectionLamps
Thehistoryofprojection,likethatofothertechnologies,isthestoryofthe
andexperiencessincetheearliestshadowplaysoncavewallsinantiquity
projectorsrangesfromsimplehomedevicestomorepowerfulunitsusedin theatresandsomeotherprofessionallocations.
Projectorlampswithsuchaninternalpressureofabove3000lbs.persquare incharereferredtoasUHPlamps(ultrahighpressurelamp,commonly mercuryarc).Ultrahighperformanceisanothermeaningoftheterm.Because ithasaveryhighlightoutputaccessibleforthesmallsurroundingsofmicro displayprojectors,itisacommonsourceoflightfordigitaldatafront projection,videofrontprojectors,andrearprojectiontelevisions.
UHPlampslightsourceshaveahigharcluminance(>1Gcd/m2),along lifetime(2000To4000hours),andalowlumendepreciation(lumenloss) overtime.Thehighbrightnessisaccomplishedbydischarginghighly pressurized(>200bar)mercuryvaporintoa1.2mmarcgapathighpower densitiesof,say,120W.Highmercury(Hg)pressurealsoimprovesthelight source ’scolorproperties.
ARClamps
Theearliestcarbon-arclampsweredemonstratedintheearly1800s.Oneof theveryfirstcommercialusesofelectricitywasarclamptechnology.An electricarc,whichisthedischargethatoccurswhenagasisionized,generates lightinanarcprojectorlamp.
Carbon-arcsystemswereutilizedextensivelyinfilmprojectors.Eventhough projectorsgloballybeganusingthenewxenonlampsintheearly1960s,all cinemasinMaltaemployedcarbonrodsfromthebeginningtotheperiodwhen videosweptoutpracticallyallcinemasinMaltabytheearly1980s.
Carbonarcshadonedrawback:therodscouldonlybeusedforalimitedtime. Cinemasemployedatwoprojectorsystemtoavoidthisdifficulty,which requiredeachprojectortoshowashortenedreelofthefilmbyswitchingfrom oneprojectortotheother.
Thiswasreferredtoasachangeoverintheindustry.Theaudiencehadnoidea whatwasgoingon,butthetwosetsofdotsappearingonscreeninthetop righthandcornerevery15minutessignaledthatachangeoverwasaboutto happentotrainedstaff.
Carbonarctechniqueemitsasignificantamountofheatandashintothe environment.Whennitratefilmwasutilizedintheearlydaysofcinema,they wereresponsiblefornumerouscatastrophicfires.
LIGHT-EMITTINGDIODE(LED)
LEDs,orlightemittingdiodes,arewellknownintoday’ssocietyfortheiruse inhomes.Thisisalightsourcemadeofsemiconductors.Energyisemittedin theformofphotonswhenvoltageisapplied.LEDshaveanumberof advantagesovertraditionallightsources,includingalonglifetime,compact size,fastswitching,andlowenergyconsumption,resultinginlessheat generation.AlthoughtherewasapushtoreplaceUHPlightswithLEDin projectors,thebiggestproblemthathinderedthisinnovationfromreally takingholdwasthatitprovidedlessbrightness.Asaresult,LEDswere relegatedtolowerbrightnessprojectorlamp.
TheFL32byProjectionDesignwasthefirstLEDprojectoronthemarket, producingroughly600lumens.TheseLEDprojectorsweretypicallyutilizedin specializedapplicationslikesimulation,wherecheapownershipcostswere
moreessentialthanlightoutput.Withalightsourcepossibletooperate 100,000hours,theFL32couldrunfornearly12yearsincontinuousoperation beforerequiringmaintenance.
SinceProjectionDesign’sprojectiontechnologyemployedDLP(atrademarkof TexasInstruments),theadoptionofLEDsallowedprojectormakerstoforgo requiringcolorwheels,removingoneofDLPonechipprojectors’limitations.
LASER-BASED
TheMitsubishiL65A90LaserVuewasthefirstcommerciallyavailable commerciallylaser-basedDLPHDTVin2008,anditalsoeliminatedtheneed foracolorwheel.Thedigitalmicromirrordevice(DMD)intheseprojectedTVs isilluminatedbythreeindependentcolorlasers,resultinginaricher,more brilliantcolorpalettethanothersystems.Purelaserhasavarietyofadvantages, mostofwhichareacombinationoftheadvantagesofthepreceding illuminationtechnologiesstatedabove.
Forstarters,youwon’thavetoreplacethelightsourceasfrequently,making theprocessmoreefficientandrequiringlesslightsourcerenewalsand maintenance.Unlikelights,Projectorlampcanbeputatanyangleor configurationwithoutcausingdamagetothelightsource.
WrappingUp
LightandProjectorlamphavealonghistorytogether.Alightsourceis requiredforeachprojector.WhileLEDandLaseralternativestoclassiclamp