Was steckt hinter dem Begriff image sticking? - Display LC

Image sticking, also known as “image retention” or “ghost image”, is a phenomenon in which the displayed image stays faintly visible after ... Author:MiloradBajic Whatis"imagesticking"?14.01.21  /M.BajicImagesticking,alsoknownas“imageretention”or“ghostimage”,isaphenomenoninwhichthedisplayedimagestaysfaintlyvisibleafterchangingthecontent.ThisphenomenonhasbeenknownsincethebirthoftheLCDdisplayandcontinuestobotherpanelmanufacturersandenduserstothisday.Imagestickingappearsinapplicationswithstaticimagecontent(icons,logos)ormenuinputfieldsthataredisplayedoveralongerperiodoftime.Dependingonthespecificimagecomposition,andthetimeofthemainsymbolsbeingdisplayedinanunchangedway,imagestickingcanoccurindifferentintensities.Ifthedisplayorthedisplayareaisusedexclusivelyforsuchapplications(representationoficonsorinputfields),thisphenomenonstaysusuallyunnoticedbecausethedisplaynevershowsothercontent.Thisphenomenononlybecomesvisiblewhenadifferentimagecontentthanthe"static"oneisshownonthedisplayandthecontrastdifferencesarehighenough(blackandwhite).  Slightimagestickingrecognizableafterchangingtograyscalepattern Theterm"burn-in"isalsomistakenlyusedasasynonymforimagesticking,whichisassociatedwiththeoldphosphor-containingtubemonitor(CRTmonitor),whereoverloadingthefluorescentlayerledtoirreversibleburn-in.Incontrastto«burnin»,imagestickingisusuallyrevisable. Whatcausesimagesticking?Imagestickingdependsonvariousfactors,suchasthespecificimagecontent,thedurationoftheunchangedcontentandthetemperatureinthedisplayitself.Thephenomenoncanevendifferfrompaneltopanelduetodifferencesinthemanufacturingprocess(processvariance).Imagestickingoccursmainlyduetotechnologicalreasonsandcanbetracedbacktothecreationofparasiticchargesintheliquidcrystalwhendisplayingstaticcontent(continuousdisplayingofthesameimage).Thischangesthecharacteristicoftheliquidcrystalandthereforeultimatelypreventstheliquidcrystalfromreturningtoitsoriginal,relaxedstatewhenchangingthecontent.Forthisreason,panelmanufacturerscannotcompletelyruleoutimagesticking.However,thepanelmanufacturerscarryoutstressteststhatprovokeimagesticking:achessboardpatternisusedforthis,whichis“burnedin”overacertainperiodoftime.Thedisplayisthenswitchedoffandchangedtoagrayscaleimageinwhichimagestickingisrecognizablebest.Dependingonthe«burn-intime»,anyexistingimagestickingshoulddisappearafterthespecifiedswitch-offtime.Withaburn-intimeof8hours,forexample,aswitch-offtimeof30minutesisusuallyspecified.Thechessboardwiththeblack-and-whitepatternprovokesthephenomenonthefastestduetothehighcontrastdifferences.Thisisbestvisibleonthegraybackground.   standardtestingimagesticking Industrialstandardtest:DriveTFTwithChesspatternfor8h@Roomtemperature→powerofffor30min→CheckTFTwithgreypicture(128scaled)→NoVisibleimagesticking  TippsforavoidingimagestickingIfitisnotpossibletoavoidcontinuouslystaticimagecontent,thefollowingtipscanhelptoavoidimagesticking: Avoidacombinationofstaticimagecontent(symbols/text)andbackgroundcolorswithlargecontrasts/brightnessdifferences(white-black).Whenusinghigh-contrastcolors,acolorgradient(grayscale)canbeimplemented.Screensavercanbeimplementediftheapplicationisinactiveforalongtime.Insertvideobetweenthestillimages.Afterlongercontinuousoperation(>8hours)switchoffthedisplayforatleast30minutes. Ifthedisplayisusedathighambienttemperatures,itshouldalsobenotedthattheimagestickingcanappearafterashorterperiodoftime.Inthiscase,werecommendequippingthedisplaywithoptimizedcoolingorswitchingthedisplayoffatshorterintervals. ConclusionThetopichasbeenknownsincethebeginningofTFTproduction,butitcanbeavoidedifafewrulesareobserved:thisway,staticcontentcanbeusedwithouthesitation(asexamplebytime-recordingterminals).Iftheimagestickingdoesappear,itcanberemediedbyswitchingoffthedisplayforafewhours,dependingontheintensity.Severalofourinternaltestsshowthatevenwithendurancestresstestsof360hourswithachessboardpattern,imagestickingdisappearscompletelyafter4hours.  360hourstestwitha 1100cd/m2TFT  Changetograyscaleimage->slightimagestickingvisibleChangetobluebackground->noimagestickingvisible Variousstudiesarecurrentlyavailablethatshowapproachesastohowthesusceptibilityofpanelproductioncanbereduced.Itisthereforetobeexpectedthatthephenomenonwillcontinuetodecreaseinthefuture. Ifyouwanttoknowmoreaboutimagestickingcontactusnowforfurtherinformation!Contact