In Cell触摸屏原理

In-Cell触摸屏原理2010.3.15Introductionoftouchpanel•1.Resistivetouchpanel1.1traditionalresistivetouchpanel(directlyglueonLCDmodule)a.4/5/6/8-wireresistivetouchpanelb.digitalresistivetouchpanel(touchswitches,matrix)1.2integrateresistivetouchpanelintoLCDcell(betweentopandbottomglasses)•2.Capacitivetouchpanel2.1capacitancechangedbydeformationoftopglass2.2capacitancechangedbyinducedcurrentfromfinger2.2.1surfacecapacitivetouchpanel2.2.2projectivecapacitivetouchpanel2.2.2.1detectselfcapacitance2.2.2.2detectmutualcapacitance•3.Othertouchpanel(Infrared,SAW,Electromagnetic,Optical…)Resistivetouchpanel基本原理：触摸时，两层ITO互相接触，从而在两层ITO之间形成电阻通路根据上下基板材料，可分为filmonglass,glassonglass,filmonfilm等结构。LCDTouchPanelPlasticfilmRigidsubstrateITOSpace1.14-wireresistivetouchpanel在两电极上加5V直流电在ITO均匀电阻平面上形成均匀稳恒电流场在另一面的ITO电极上测量电压根据测得电压值（0-5V）确定触摸点的位置用同样方法测量Y坐标ITO+5VTouchpointMeasureXXYITOITO+5VTouchpointMeasureYITO1.14-wireresistivetouchpanelLowlifetime(around1milliontimes)Lowtransmissivity(75%-85%)NotresistscratchLowestcostEasydetectcircuitWorkswithanystylus1.2Incellresistivetouchpanel—samsung(1)•Basicprinciple:Whenpressed,thesensorswitchison(conductivecolumnspacercontactsensorelectrode)Fromplanview,attouchpoint,commonelectrodecontacttwosensinglinesperpendicularwitheachotherrespectively•2.Capacitivetouchpanel2.1capacitancechangedbydeformationoftopglass2.2capacitancechangedbyinducedcurrentfromfinger2.2.1surfacecapacitivetouchpanel2.2.2projectivecapacitivetouchpanel2.2.2.1detectselfcapacitance2.2.2.2detectmutualcapacitance2.1Capacitivetouchpanel(压力式)•Thisintegratetypehassomedifferentstructures,includes:–CellgapchangetypeSamsungfiledapatent(US20080048994).AUOhasmadeademo.–LCalignmentchangetypeSamsungfiledpatent(US20050094038)veryearly,butSamsung’sdemoappliedanotherdetectcircuit(SID0724.3),andEpsonmadeademo(SID0855.2)basedonSamsung’sstructurebyusingLTPS,IPSandactivematrixsensorsothatimprovedtheperformance.Cellgapchangetype(1)•Samsung’spatent(US20080048994)onlyposedabasicprinciple,itslayerstructureanddetaileddetectmethodisnotshowninthepatent.•ThoughAUOhasmadeademo,thereareveryfewopenmaterialsofitsdetectprinciple.•Theyusethesameprinciple:detectthecapacitancechangebetweencommonelectrodeandsenseelectrodebycellgapdeformation.•Therearemanywaystodetectcapacitancechange,whichwaySamsungandAUOusedisunknown.AUOSamsungCellgapchangetype(2)•AUO和LG的压力式内嵌触摸屏样品LCalignmentchangetype—Samsung(1)•Samsung’spatent(US20050094038)firstproposedthismethod:BecausedifferentLCalignmenthasdifferentdielectricconstant,andwhenpressed,theLCalignmentischanged,sothattheLCcapacitancechanged.LCalignmentchangetype—Samsung(2)•Samsung和Epson的in-cellLCalignmentchangetypeTPSamsungEpson2.2.1Surfacecapacitivetouchpanel•Have2conductivecoatings.Upperconductivecoatingistheworkingplane.•Lowercoatingisshieldingplane.ProtectiveovercoatConductivecoatingElectrodepatternConductivecoatingGlasssubstrateSurfacecapacitivetouchpanelSurfacecapacitivetouchpanelprinciple:Touchpointistreatedasconnectingtogroundbyacapacitor.Theresistorfromtouchpointto4cornersR1-4isrelatedtothedistancefromtouchpointto4corners.Themorethedistanceis,themoretheresistoris.Whenaddsinesignalon4corners,thecurrentat4cornersI1-4isinverseproportiontorelatedR1-4.BymeasuringI1-4,thetouchpointcanbedetected.SurfacecapacitivetouchpanelLonglifetime(around100milliontimes)Highertransmissivity(Canreach90%)OnlyworkwithfingersHighercostPatentissueComplexdetectcircuitFastresponsespeed2.2.2投射电容触摸屏(PCT)投射电容触摸屏（projectivecapacitivetouchpanel）可分为两种不同的结构：自电容(selfcapacitive)与互电容(mutualcapacitive)自电容为较早的技术，来源于touchkey,touchpad互电容技术由iphone发扬光大，发展迅猛，将逐渐取代自电容类型Selfcapacitance自电容原理为当手接触时，等效为parasiticcapacitance增加，而且自电容检测都是在前端（提供电源端）。检测原理有很多，可检测电压、电流、电荷，下图为chargetransfer检测原理。通过开关依次开合不断对parasiticcapacitance进行充电放电，检测放电时通过的电荷，当有手指接触时，流出电荷增加。Detectselfcapacitance•Panellayout:generallyusing‘diamond’pattern,sothecapacitorfromfingertobothITOlayerswillbebigenough.Thedetectsequenceis,firstdetectselfcapacitanceatonelayer(red),onelinebyoneline,togetXposition,thendetectanotherlayer(blue),togetYposition.Sothisisfakemulti-touch.Projectivecapacitivetouchpanel自电容的多点触摸定位问题：Mutualcapacitance互电容原理为：当手指接触时，等效为互电容改变，互电容检测一般是在后端（sense端）。可以检测电压或者电荷。下图为电荷检测等效电路。手指接触后等效为互电容减小，此时读出电荷减小。模型一MutualcapacitancePanel图案MutualcapacitanceDrivingmethod:Atdrivelayer(red),addpulsesignalonelinebyoneline,andotherlinesconnecttoground.Atsenselayer(blue),detectchargeonebyone.Whenallintersectionisdetected,themostchargedecreasedintersectionisthetouchpoint.Thismethodistruemulti-touch.Soappleclaimedthatiphoneisthefirst‘imagesensing’touchpanelintheworld.上表面和下表面diamond是错开的模型仿真结果NotouchTouch互电容的优点互电容相对自电容的显著优点：1.对地寄生电容对触控检测影响很小，更适合在集成触摸屏结构2.具有更强的抵抗LCD噪声能力3.可以实现真正的多点触摸（不会有鬼点）但互电容是一个更加新的技术，目前几乎所有触控IC厂商采用的感应技术都不一样，各自研发自己的触控技术。Othertouchtechnology红外：透光度好，价格低，适应恶劣环境缺点：分辨率较低，易损坏在屏幕四边排布红外发射管和红外接收管，一一对应形成横竖交叉的红外线矩阵。用户在触摸屏幕时，手指就会挡住经过该位置的横竖两条红外线，因而可以判断出触摸点在屏幕的位置。Othertouchtechnology声表面波：透光好，寿命长缺点：易被油污，灰尘等影响，需经常维护X轴发射器X轴接收器反射阵列可触摸区域吸收残波胶带Y轴接收器Y轴发射器当手指或其它能够吸收或阻挡声波能量的物体触摸屏幕时，X轴途经手指部位向上走的声波能量被部分吸收，反应在接收波形上即某一时刻位置上波形