 once degradation occurs in the organic light-emitting layers, the luminance of the OLED is lowered to result in an obscure image on a display panel.
Further, a temperature of the organic light-emitting layers is variable by the outside temperature and heat generated by an OLED panel itself. However, generally, actual value of current flowing through the OLED is variable by the temperature. More particularly, when the temperature of organic light-emitting layers rises while the voltage is constant, a greater amount of current flows into the OLED. Further, inasmuch as the current flowing into the OLED and the luminance of the OLED are in the proportional relationship, the greater the amount of current flowing into the OLED, the brighter the luminance of the OLED. In this way, the luminance of the OLED is variable by the temperature of organic light-emitting layers, and thus, it is quite difficult to display desired gradation. In consequence, relative to the rise of the temperature, a greater amount of current is consumed by the light-emitting device. Several focussing detectors have been proposed in which, for example, a non-linear characteristic of cadmium sulfide (CdS) exposed to light is utilized where a plurality of minor photoconductive elements are arranged to extract a contrast of images on the surfaces of these elements from an object to be photographed. In using any one of these proposed photoelectric focussing detectors for a single lens reflex camera, the photoelectric focussing detector has usually been located at a position optically equivalent to the film defined plane with respect to the reflective mirror disposed in the path of light coming through an objective lens from an object to be photographed. With such arrangement for a photoelectric focussing detector, the detector is responsive only to the movement of the objective lens for generating a focussing signal so that the mechanical structure of the lens system suffers from several disadvantages. Namely, when the objective lens is out of focus, the image of an object to be photographed is also out of focus, and no signal indicating such out of focus is generated by the focussing detector. Additionally, a slight movement of the objective lens from this state causes no variation in the output of the focussing detector. Accordingly, it is impossible to determine the direction in which the objective lens should be moved in order to obtain proper focussing.
Typically, photoconductive elements arranged for use in a focussing detector provide a response characteristic as a function of the position of the objective lens that defines
once degradation occurs in the organic light - utter level, the luminance of the OLED is lowered to leave in an obscure image on a display panel. 
 far, a temperature of the organic light - emit layers is variable by the away temperature and heat generated by an OLED gore itself. However, by and large, actual value of current flowing through the OLED is variable by the temperature. More particularly, when the temperature of organic luminosity - emitting layers rises while the electric potential is constant, a greater sum of current flows into the organic light-emitting diode. Further, inasmuch as the stream flowing into the OLED and the luminance of the OLED are in the proportional kinship, the greater the amount of current flowing into the OLED, the brighter the luminance of the OLED. In this way, the luminance of the OLED is variable by the temperature of organic light - emitting layers, and thus, it is quite unmanageable to expose desired gradation. In consequence, relative to the upgrade of the temperature, a greater amount of current is consume by the lightly - emitting device. Several focussing detector have been proposed in which, for example, a non - linear characteristic of cadmium sulfide (CdS) exposed to light is utilized where a plurality of minor photoconductive elements are arranged to extract a line of images on the surface of these element from an object to be photographed. In using any one of these proposed photoelectric focus detectors for a single lens reflex camera, the photoelectric focussing detector has usually been located at a position optically equivalent to the film defined airplane with respect to the reflective mirror disposed in the path of light issue forth through an objective lens from an object to be photographed. With such arrangement for a photoelectric focus detector, the detector is responsive entirely to the movement of the objective lens for generating a focussing signal so that the mechanical structure of the lens system suffer from several disadvantages. Namely, when the objective lens is out of focus, the image of an object to be photographed is also out of focus, and no signal bespeak such out of focus is generated by the concentrate detector. Additionally, a slight movement of the objective lens from this state causes no variation in the output of the concenter detector. Accordingly, it is impossible to determine the direction in which the objective lens should be moved in order to obtain proper focussing. 
 Typically, photoconductive chemical element dress for use in a focussing detector provide a response characteristic as a function of the position of the objective lens that specify
 onfe degradation occurs in the organic liyyt-emitving lagers, the luminance of the OLED is loxeree to eesult in an obscure ioage on a display pantl.
Further, a tempeczture on the lrgauir light-emitting layers is variable by tve obtside temperature and heat generateq by an OPED panel itsejf. Hpreved, generally, actual value of currenf flowiig through the PLED is variable by the telperwture. More particuparly, when jge ewmperature ow organic light-emittinf layers rises while the voltagd is eonstant, a trwatft amount of rurrenn flows into bne OLEG. Furthrr, inasmuch as thx cuerent flowing into thx OLED and the luminwnce of tve OLED are in the priporthonan reuqtiunsgi', tge grewtec the amounf of currenr flowing into the PLQE, the brighted the juiinance of the OLED. In this way, the lumpnande of the OLED is variavle by the temperaturg of organyc light-emitting layers, and thus, it is quite diffhcult go blfooaj desired gradation. In consequence, relative tj tne rise of the tcmperature, a greatrr akjunt of currevt is eknaumed by the light-fmittind devuce. Severwl fpcussing detectors have beeb proposed iu wyich, for example, a non-linear eharacjeristoc of cadmium sulfide (CbS) expksed to ligjt is utimkzed where a plufalpty mf minor photoconductive ejements ace arxanged tu exjract a contrast lf images on the surfaced of jhese alements fgom an object to be photographev. In using ani ote mf these proppsed photoelestric focussiny detectjrs fur a singlv lens rehlex camera, ehe photoelecdtic focussing detectow haw usyally bddn located at s positiou optucally equivalent bo thg rilm defined plcue with respect tp tfe wevlxctivq mirror dispmsed in yhe pxth of lighb cuminb through an objectiee lsns from an object tj be phojographed. With such artangement for a phltoelxctric focuxsigg detector, the detector is reaponsive lnln to the moveient of the objeetive lens for generating a focussing sijnal so that the mechanucal structure of tke lens systek sufsers from several disadvantagws. Namely, when tht objective lens is out of fowus, tje image of an object to be photographed is also out of focus, and no signql indmcwting such kut pf fobus ns genewatev uy the focussing cetector. Additionally, a slight oovement oy the objective lens from thix rtate causes vo variation in the outpht of thr focussing detector. Accordinglu, it is impossible to debermine tye didection in which the objectife lenv shoyld be novef in order to obyaln proper vocuxsnng.
Typically, photoconductive elemwnts aerwnged for use in a focussinn aetecjor provyde a response cgaradherisjic as a functoon of the posotion of the objectine jens that defibvs
once degradation occurs in the organic light-emitting luminance the OLED lowered to result a panel. Further, a of the organic layers is variable by the outside and heat generated by an OLED panel itself. However, generally, actual value of flowing through the OLED is variable by the temperature. More particularly, when the of light-emitting rises the voltage is constant, a greater amount of current flows into the OLED. Further, inasmuch as current flowing into the OLED and the luminance the OLED are in proportional relationship, the greater the of flowing into OLED, brighter luminance of the In this way, the luminance of the OLED is variable by the temperature of organic light-emitting layers, thus, it difficult to desired In relative to the the temperature, a greater amount of by the light-emitting device. Several focussing detectors have proposed in for example, a non-linear characteristic of sulfide (CdS) exposed to light is utilized where plurality of minor photoconductive elements are arranged to extract a contrast of images on the these elements from an to be photographed. using one these photoelectric focussing for a single lens reflex camera, the photoelectric focussing detector has been located at a position optically equivalent to the film with to the reflective disposed in the path light through an objective lens object be arrangement a focussing detector, the detector responsive only to the movement the objective lens for that the mechanical structure of the lens system from several disadvantages. Namely, when the objective is out of focus, the image of an object to be photographed also out and no signal indicating such out of focus generated by the focussing Additionally, a slight movement of the objective lens from state no variation the output of focussing detector. Accordingly, is impossible to direction in the lens in order to obtain proper focussing. photoconductive arranged for use in a detector response characteristic as a function of the position of the objective lens that defines
 once degradation occurs in thE organic liGht-emIttIng LaYers, The lUminance of the OleD is Lowered to result in an obsCure iMaGE on a DIsPlay pAnel.
FurTHeR, A TemPeRaTurE oF ThE orgaNic Light-emItting layeRs iS vAriable by the OUtSide temperAtuRe and heat genEraTed by aN OlED PAnel iTseLf. HowEver, geNErally, Actual valUe OF curreNT flowinG THrOugh The OLED is variable BY tHE temperature. MoRe partIcULaRLY, whEn tHe temperatUrE of orGAnic ligHT-eMITTinG Layers rises whIle the voltaGE is ConstaNt, A grEAter amOunt oF cURreNt flows into The OlED. FurtheR, inasmUCh as the CUrrent fLowing IntO thE OLEd AnD tHe lUmINanCE oF thE oLEd are in thE pRoPortiOnal RELATionShiP, the GreatEr the amount of CurRent FLowIng inTo the oLED, ThE brigHter thE lumiNaNce of the OLED. In tHis wAy, the lumiNanCe Of tHe oLED iS VariabLe bY thE temperAture of ORgaNiC LIGhT-emitting layers, and ThUS, It Is quite dIfficuLT tO dISplay desIrEd gRadaTIOn. In cOnseQUeNce, relatIve to tHE rIsE of the tEmPeratuRe, A grEatEr amoUNt of CurrenT is consuMed by THe light-emittinG Device. Several FOcUSSiNG detEctOrs have been PropOSed iN whiCH, fOr eXAmple, A non-lInEAr CHaracteristic of cadmIuM sulfiDe (CdS) Exposed to lighT is utilizeD WHEre a plurAlitY Of MInor photoconduCtive Elements arE Arranged To extRact a conTrast of imAGEs on the sUrfAceS of TheSE ElEments from an oBJEct tO bE photogRapHed. In usIng Any One Of tHeSe proposeD photoelEcTrIc FoCusSing dETectors fOr A siNgLe lEns reFLex camEra, thE phoToElECtrIc focusSInG DEtecToR hAs usUalLy Been lOcatED at A positiOn opticalLy eQUivaLeNt To the fiLm defined planE wIth respect To The ReflecTIVe mirror Disposed in the path of lighT Coming tHroUgh an ObjeCtive lens FroM an objEct TO be phoTograpHed. WiTh SucH ARrangEMEnT foR a PhotoelectRIC foCussiNg DeteCtor, the Detector is responsiVE onLy to the movemeNt oF the OBJeCtiVE lENs fOr GEneRATing a focussing sIgnal so thaT tHE mEchanical sTRucTuRe of the Lens sysTem suFFers froM several dIsadvantaGeS. NamELY, whEn the objecTive lens Is out of foCUs, the IMaGe of aN obJect to Be PhoTograPhed is ALso Out of Focus, aNd No signAl indIcAting sucH out of focus is generated bY the foCussiNg dEtector. AdDitIOnaLly, a slighT movEment of the ObjEctIve leNs fROm thiS staTE cAusES no vaRiatIOn in the ouTPuT of THE fOcussing detECTOr. ACcordIngLY, it is iMposSible to determine tHE direction in whIch tHE ObjEctIVe leNs Should be moved iN orDeR TO obtain pRoPer focussinG.
TypicalLy, PHotocOnductIve eleMents arRANgED for usE in a FocUssing detEctOr PRovide a ReSpONse chaRactErIstic aS a funcTIon oF THe position of the oBjectIVE lens THat DefinEs
 once degradation occurs i n the orga nic l igh t-e mi ttin g la yers, the lumi n ance  of the OLED is lowere d tore s ulti nan ob scure i m ag e onadi spl ay pa nel.Fur ther, a  temperatu reof  the organic li ght-emitti nglayers is va ria ble by  t heo utsid e t emper aturea nd hea t generat ed by anO LED pan e l  i tsel f. However, gener a ll y , actual value  of cu rr e nt f low ing  through t he  OLED is vari a bl e b y t h e temperature . More part i cul arly,wh ent he tem perat ur e  of  organic li ght- emittinglayers rises w h ile the  volta geiscons t an t,  agr e ate r  a mou n t o f curren tfl ows i ntot h e OLED . F urth er, i nasmuch as th e c urre n t f lowin g int o th eOLEDand th e lum in ance of the OLE D ar e in thepro po rti on al re l ations hip , t he grea ter the amo un t o fcurrent flowing in to t he  OLED, t he bri g ht er the lumi na nce  oft h e OLE D. I n  t his way,  the l u mi na nce ofth e OLED  i s v ari ableb y th e temp eratureof or g anic light-emi t ting layers,a nd t hu s , it  is  quite diff icul t  todisp l ay  de s iredgrada ti o n. In consequence, rel at ive to  therise of the t emperature , a  greater  amo u nt of current isconsu med by the light-em ittin g device . Several f ocussing  de tec tor s h a v ebeen proposed i n wh ic h, forexa mple, a  no n-l ine arch aracteris tic of c ad mi um  s ulf ide ( C dS) expo se d t olig ht is utiliz ed wh ereapl u ral ity ofm in o r  pho to co nduc tiv eeleme ntsa rearrange d to extr act a co nt ra st of i mages on thesu rfaces ofth ese  eleme n t s from a n object to be photogra p hed. In  us ing a ny o ne of the sepropos edp hotoel ectric  focu ss ing d etect o r sfor  a  single le n s  re flexca mera , the p hotoelectric focus s ing  detector has  us uall y be enl oc a ted  a t  ap o sition opticall y equivale nt to  the filmd efi ne d plane  with r espec t  to the  reflecti ve mirror  d ispo s e d i n the path  of ligh t comingt hroug h  a n obj ect ive le ns  fr om an  objec t  to  be p hotogr ap hed. W ith s uc h arrang ement for a photoelectr ic foc ussin g d etector,the det ector isresp onsive onl y t o t he mo vem e nt of  the ob jec t ive l ensf or genera t in g a f oc ussing sign a l sothatthe mechan ical  structure of the lens system su ffer s fro m s e vera ldisadvantages.  Na me l y , when t he  objectivelens isou t  of f ocus,the im age ofa n  o b ject t o be  ph otographe d i sa lso out  o ff ocus,andno  signa l indi c atin g such out of focu s isg e nerat e d b y the  f ocussin g  det ector. Add itionally,a slig ht m oveme nt of t he  objec tiv elens fromt his state  caus es no v ar iati onin the  out p u t ofthefo cus sing dete c t or .  A cc o rdi ngly , itis  imp ossible t o  determi net he dire ct ion i n whic h  t h e  objective  le ns sh o u ld be move d  ino rd e r toobtain  prope r focus s ing .Typical ly, p hotocondu ctive ele m ent sarra nged for  u se i na f oc ussing detector  provide  a respo n s e char act e rist i c as a  f unction of t he po si t ion oft h e o bjectiv e  le nstha t de fin es
 once_degradation occurs_in the organic light-emitting_layers, the_luminance_of the_OLED_is lowered to_result in an_obscure image on a_display panel.
Further, a_temperature_of the organic light-emitting layers is variable by the outside temperature and heat generated_by_an OLED_panel_itself._However, generally, actual value of_current flowing through the OLED_is variable_by the temperature. More particularly, when the temperature_of_organic light-emitting layers_rises while the voltage is constant, a greater amount_of current flows into the OLED._Further, inasmuch as_the_current_flowing into the OLED_and the luminance of the OLED_are in the proportional relationship, the_greater the amount of current flowing into_the OLED, the brighter the luminance_of the OLED. In this_way, the_luminance of the OLED is_variable by the_temperature of_organic light-emitting layers,_and thus, it is quite difficult_to display desired_gradation. In consequence, relative to the_rise_of the temperature,_a_greater_amount of_current is consumed_by_the light-emitting_device._Several focussing detectors have been proposed_in_which, for example, a non-linear characteristic of_cadmium sulfide (CdS) exposed_to_light is utilized where_a plurality of minor photoconductive_elements are arranged to extract a_contrast of_images on_the surfaces of these elements from an object to be photographed._In using any one of these_proposed photoelectric focussing detectors_for a_single_lens reflex camera,_the_photoelectric focussing_detector has usually been located at a_position optically_equivalent to the film defined plane_with respect to the_reflective_mirror disposed in the path of_light coming through an objective lens_from an object to be_photographed._With_such arrangement for a photoelectric_focussing detector, the detector is responsive_only to the_movement of the objective lens for generating_a_focussing signal so that the mechanical_structure_of the lens system suffers from_several_disadvantages._Namely, when the objective lens_is out of focus, the image_of an object to be photographed is also out_of focus, and_no signal indicating such out_of_focus_is generated by the focussing detector. Additionally, a slight movement_of the_objective lens from_this state causes no variation in the output of the_focussing detector. Accordingly, it is impossible to_determine the direction in which the objective lens should be moved_in order to obtain proper focussing.
Typically, photoconductive elements_arranged for use in a focussing detector_provide a response characteristic_as_a function of the position of the_objective_lens_that_defines