Philips BDL4677XL Home Theater Screen User Manual


  Open as PDF
of 41
 
BDL4677XL
27
6.4. Dark Dot Defects
Blackdotdefectsappearaspixelsorsub-pixelsthatarealwaysdarkor“off”.Thesearetheexamplesofblackdotdefects:
Onedarkdot Twoadjacentdarkdots=1pairofdarkdots Twodarkdots,specicationsdenesthe
minimumdistancebetweendarkdots
6.5. Proximity of Pixel Defects
Becausepixelandsub-pixelsdefectsofthesametypethatarenearbyoneanothermaybemorenoticeable,Philipsalsospeciestolerancesforthe
proximityofpixeldefects.Inthetablebelowyoucanndspecicationsabout:
• Allowedamountofadjacentdarkdots=(adjacentdarkdots=1pairofdarkdots)
• Minimumdistancebetweendarkdots
• Totalno.ofalldefectivedots
6.6. Pixel Defect Tolerances
Inordertoqualifyforrepairduetopixeldefectsduringthewarrantyperiod,aPDP/TFTpanelinaPhilipsPlasma/LCD-displaymusthavepixelorsub-
pixeldefectsexceedingthetoleranceslistedinthefollowingtable.
BRIGHTDOTEFFECT ACCEPTABLELEVEL
1litsubpixel 2
BLACKDOTEFFECT ACCEPTABLELEVEL
1darksubpixel 10
TOTALDOTDEFECTSOFALLTYPES 12
NOTE:*1or2adjacentsubpixeldefects=1dotdefect
6.7. MURA
Darkspotsorpatchesmayoccasionallyappearonsomeliquidcrystaldisplay(LCD)panels.ThisisknownwithintheindustryasMura,whichisaJapanese
termfor“unevenness.”Itisusedtodescribeanirregularpatternorareainwhichunevenscreenuniformityappearsundercertainconditions.Muraisa
resultofthedeteriorationoftheliquidcrystalalignmentlayerandismostcommonlycausedbylong-termoperationunderhighambienttemperatures.It
isanindustry-widephenomenonandMuraisnotrepairable.Itisalsonotcoveredbyourwarrantyterms.
MurahasbeenaroundsincetheintroductionofLCDtechnologyandwithscreensgettingbiggerandinoperation24/7,manydisplaysarerunninginlow
lightconditions.ThisalladdstothepossibilityofMuraaffectingdisplays.
HOW TO SPOT MURA
TherearemanysymptomsofMuraandalsomultiplecauses.Severalofthesearelistedbelow:
• Impuritiesorforeignparticlesinthecrystalmatrix
• UnevendistributionofLCDmatrixduringmanufacturing
• Non-uniformluminancedistributionofthebacklight
• Panelassemblyinducedstress
• FlawswithintheLCDcells
• Thermalinducedstress-hightemperatureoperationoverlongperiodsoftime
HOW TO AVOID MURA
AlthoughwecannotguaranteethecompleteeradicationofMuraeverytime,ingeneraltheappearanceofMuracanbeminimizedbythesemethods:
• Lowerthebacklightbrightness
• Useascreensaver
• Reducetheambienttemperaturearoundtheunit
 previous next