 the invention, the document end detecting unit detects a shade appearing at the slot of the back member due to an end of a document, and detects either end of the document based on a result of detecting the shade. This allows appearance and disappearance of a shade to be detected with reliability, so that reliability on detection of either end of a document in the document end detecting unit according to the invention is increased enough to be more practicable than a conventional document end detecting unit which uses a back member having no slot.
In the document end detecting unit of the invention it is preferable that the detecting means detects disappearance timing of a shade of the downstream end in the moving direction of the document and regards the detected disappearance timing as timing when the downstream end in the moving direction of the document reaches the reference position.
According to the invention, in the document end detecting unit, the detecting means regards a detected disappearance timing of a shade of a downstream end in the moving direction of a document as timing when the end reaches the reference position. Timing when the downstream end in the moving direction of the document reaches the reference position coincides with disappearance timing of a shade. This enables the document end detecting unit to most reliably detect the downstream end in the moving direction of a document based on a shade appearing at the slot of the back member.
In the document end detecting unit of the invention it is preferable that the detecting means detects appearance timing of a shade of the downstream end in the moving direction of the document and regards a point in time when the document has relatively moved a predetermined distance from a position thereof at the detected appearance timing as timing when the downstream end in the moving direction of the document reaches the reference position.
According to the invention, in the document end detecting unit, the detecting means detects timing when the downstream end in the moving direction of the document reaches the reference position based on only appearance timing of shade of the downstream end in the moving direction of the document. This simplifies the construction for detecting a shade of a document end, so that the entire construction of the document end detecting unit is simplified.
In the document end detecting unit of the invention it is preferable that the color of the surface of the back member and the inner wall of the slot is white;
the light-receiving means is composed of a plurality of light-receiving elements arranged in parallel to a direction which is substantially orthogonal to the moving direction of the document;
light reflected from the slot of the back member and light reflected from the surface of the back member excluding the slot
the invention, the document end detecting unit detects a ghost appear at the slot of the back member due to an end of a text file, and detects either end of the document based on a consequence of detecting the shade. This allow appearance and disappearance of a shade to be detect with reliability, so that reliability on detection of either end of a text file in the document end detect unit harmonize to the invention is increase enough to be more practicable than a conventional document conclusion detecting unit which uses a back member have no slot. 
 In the document end detecting unit of the invention it is preferable that the detection means detects disappearance timing of a shade of the downstream end in the moving direction of the text file and see the detected disappearance timing as timing when the downstream end in the moving direction of the document reaches the reference position. 
 According to the invention, in the text file end detect unit, the detecting means involve a detected disappearance timing of a shade of a downstream goal in the moving direction of a document as timing when the goal reaches the reference position. Timing when the downstream end in the moving direction of the text file reaches the reference position coincides with disappearance timing of a shade. This enables the text file end detect unit of measurement to most reliably detect the downstream end in the move direction of a document based on a ghost appearing at the slot of the back member. 
 In the document conclusion detecting whole of the invention it is preferable that the detecting means detect appearance timing of a shade of the downstream end in the moving direction of the text file and regards a point in meter when the document has relatively moved a bias distance from a position thence at the detected appearance timing as timing when the downstream end in the moving direction of the text file reaches the reference position. 
 According to the invention, in the text file end detecting unit, the detecting means detects clock when the downstream end in the moving direction of the document reaches the reference position free-base on only appearance timing of shade of the downstream end in the moving direction of the document. This simplifies the structure for detecting a shade of a document end, so that the entire construction of the document end detect unit is simplified. 
 In the document end detecting unit of the invention it is preferable that the color of the surface of the back member and the inner rampart of the slot is white; 
 the light - receiving means is composed of a plurality of light - meet elements arranged in parallel to a direction which is substantially orthogonal to the act direction of the document; 
 light reflected from the slot of the back member and light reflected from the surface of the back member excluding the time slot
 thf invention, the document end detecting onut detxcts a ahade apoearing at the slot of the beck nembee due to an end of a ducument, ajd detecrs emther end of the documenb bassf on e result of detgcting the svade. This allofs a'pearance and disappearance of a shaqe to br fetected with telianylitg, so that reliability on detection of eitier end of a dovument in the document end detfcting unit accordlng to the unvegrion is incrdased enough to be morg practicable than a conventionau docbment end dgcwctltg unit whirh usef a back memnvr havitg no skot.
In the docukenv ene detecting unit of tie invention it is pteferable dhct the detecting meanw eetecjs divappdqravce tmmihg of w siade of the downstream end in the moving ciwvvtion of the documqne and regards the detected disappearanct timjng as timing when the eownstream end in the moving dyrection of the document reaches the reference povitioi.
Azcoxeing gi hhe invention, in the document end detecting ugjt, tme detecting meaks regards a detecyef cysappearance jiming of z shade of a downshream egd in the movigg dorection of a document as tuming when tke wnd reaches the reyerence posicion. Toming when the downstream enb in tge moving dlrection kw the document rdacmes the reftfence position coyncides wmth dnsappearxnce timind of a shafe. Thlv enables the doculent gnd dedecting unlt to most reliably detect the vpwnstream enc hn nhe moviny diregtion of a docuient based on c shade cppearkng at the slot oh the back mqmber.
In the dmfument end dxtecting tnit of rhe invdvtion it is prrferable nhct the derecting means detegts akpsarance timing if q shade of the cowvstwewm egg in the movhng airdvtion of the docmmevt amd regards a point it tije when the documemt has relqtively ioved a predeyermined distance vrom e posivion tnergof at the detected appearance fiming as tiiing when thq doqnstream end in the moving direction of the documenv reaches the referencg position.
According tp the inventmon, in the docukent end detecting ubit, the detecting means detects timing when dhe dlwnstream end in the moving direction of the document reaches the referenxe posmtyon based oh onky apieaxanee timigg oh rhade of the dowmstream end in the moving direcvion of tha bocument. This simplifies the vovstruction fot detecting a shade of a dkcument rnd, so that the entire construcyion of the document end detectibg unjt is simpuified.
In the documrnt enb detexting ubit lf the inventkon ib is prefegablt thct the color of the surface of thw back mfmber and the inier wall of bht slot ps whitg;
the light-receivihg mswns ir composed of a plurality og light-receiving elekegts arranged ib parallel to a ditzbtion which ix substantidlly orthogonal to the moving direction of the docujent;
light reflectcd from the slot ph the back member and linht rqflected from the susface of the back member excluding the slot
the invention, the document end detecting unit shade at the of the back of document, and detects end of the based on a result of detecting shade. This allows appearance and disappearance of a shade to be detected with so that reliability on detection of either end of a document in the end unit to invention is increased enough to be more practicable than a conventional document end detecting unit which a back member having no slot. In the end detecting unit of invention it is preferable that detecting detects disappearance of shade the downstream end the moving direction of the document and regards the detected disappearance timing as timing when the downstream in the of the reaches reference According to the the document end detecting unit, the a detected disappearance timing of a shade of downstream end the moving direction of a document timing when the end reaches the reference position. when the downstream end in the moving direction of the document reaches the reference position disappearance timing of a This enables the end unit most detect the end in the moving direction of a document based on a appearing at the slot of the back member. In the detecting of the invention is preferable that the means appearance timing of a the end direction the and regards a point time when the document has moved a predetermined distance the detected appearance timing as timing when the end in the moving direction of the reaches the reference position. According to the invention, in the document end unit, the detects timing when the downstream end in the direction of the document the reference position based on only appearance timing of of downstream end the moving direction the document. This the construction for shade of document so construction of the document end detecting is In the document end detecting of it is preferable that the color of the surface of the back member and the of the slot is the means is composed of a plurality of light-receiving elements arranged in parallel direction which is moving of the light reflected from the of the back member and light reflected from surface of back slot
 the invention, the document enD detecting Unit dEteCts A sHade AppeAring at the slot OF the Back member due to an end of A docuMeNT, and DEtEcts eIther enD Of THE doCuMeNt bAsED oN a resUlt Of detecTing the shaDe. THiS allows appeaRAnCe and disapPeaRance of a shadE to Be deteCtEd wITh relIabIlity, So that REliabiLity on detEcTIon of eITher end OF A dOcumEnt in the document eND dETecting unit accOrding To THe INVenTioN is increasEd EnougH To be morE PrACTIcaBLe than a convenTional documENt eNd deteCtIng UNit whiCh useS a BAck Member havinG no sLot.
In the dOcumenT End deteCTing uniT of the InvEntIon iT Is PrEfeRaBLe tHAt The DEteCting meaNs DeTects DisaPPEARancE tiMing Of a shAde of the downsTreAm enD In tHe movIng diRectIoN of thE documEnt anD rEgards the detectEd diSappearanCe tImIng As TiminG When thE doWnsTream enD in the mOVinG dIRECtIon of the document reAcHES tHe refereNce posITiOn.
aCcording To The InveNTIon, in The dOCuMent end dEtectiNG uNiT, the detEcTing meAnS reGarDs a deTEcteD disapPearance TiminG Of a shade of a dowNStream end in thE MoVINg DIrecTioN of a documenT as tIMing When THe End REacheS the rEfEReNCe position. Timing wheN tHe downStreaM end in the moviNg directioN OF The documEnt rEAcHEs the reference PositIon coincidES with disAppeaRance timIng of a shaDE. this enabLes The DocUmeNT EnD detecting uniT TO mosT rEliably DetEct the dOwnStrEam End In The moving DirectioN oF a DoCuMenT baseD On a shade ApPeaRiNg aT the sLOt of thE back MembEr.
in THe dOcument ENd DETectInG uNit oF thE iNventIon iT Is pReferabLe that the DetECtinG mEaNs detecTs appearance tImIng of a shadE oF thE downsTREam end in The moving direction of the DOcument And RegarDs a pOint in timE whEn the dOcuMEnt has RelatiVely mOvEd a PREdeteRMInEd dIsTance from a POSitIon thErEof aT the detEcted appearance timINg aS timing when thE doWnstREAm End IN tHE moViNG diRECtion of the documEnt reaches ThE ReFerence posITioN.
ACcordinG to the iNventIOn, in the Document eNd detectiNg Unit, THE deTecting meaNs detectS timing whEN the dOWnStreaM enD in the MoVinG direCtion oF The DocumEnt reaChEs the rEfereNcE positioN based on only appearance tIming oF shadE of The downstReaM End In the moviNg diRection of tHe dOcuMent. THis SImpliFies THe ConSTructIon fOR detectinG A sHadE OF a Document end, SO THat The enTirE ConstrUctiOn of the document enD Detecting unit iS simPLIfiEd.
IN The dOcUment end detectIng UnIT Of the invEnTion it is preFerable tHaT The coLor of tHe surfAce of thE BAcK Member And tHe iNner wall oF thE sLOt is whiTe;
ThE Light-rEceiViNg meanS is comPOsed OF A plurality of lighT-receIVIng elEMenTs arrAnGed in paRAlleL to a directIon which is sUbstanTialLy ortHogonal To The movIng DiRection of tHE document;
Light ReflectEd From The Slot of The bACK membEr anD lIghT reflecteD FRoM ThE sURfaCe of The baCk MembEr excludiNG the slot
 the invention, the docume nt end det ectin g u nit  d etec ts a  shade appeari n g at  the slot of the backmembe rd ue t o  a n end  of a d o cu m e nt,  a nd  de te c ts  eith erend ofthe docume ntba sed on a res u lt  of detect ing  the shade.Thi s allo ws  ap p earan ceand d isappe a ranceof a shad et o be d e tectedw i th  rel iability, so that re l iability on de tectio no fe i the r e nd of a do cu menti n the d o cu m e n t e n d detecting u nit accordi n g t o thein ven t ion is  incr ea s edenough to b e mo re practi cablet han a c o nventio nal do cum ent  end de te cti ng uni t  w hic h  us es a bac kme mberhavi n g n o sl ot. 
Inthe d ocument end d ete ctin g  un it of  theinve nt ion i t is p refer ab le that the det ecti ng meansdet ec tsdi sappe a rancetim ing  of a s hade of the  d o w n st ream end in the mo vi n g  d irection  of th e  d oc u ment and  r ega rdst h e det ecte d  d isappear ance t i mi ng  as tim in g when  t hedow nstre a m en d in t he movin g dir e ction of the d o cument reache s  t h e  r e fere nce  position.Acco r ding  tot he  in v entio n, in  t h ed ocument end detecti ng  unit,  thedetecting mea ns regards a detected  dis a pp e arance timingof ashade of a downstre am en d in the  moving d i r ection o f a  do cum ent a stiming when t h e  end  r eachesthe  refere nce  po sit ion .Timing wh en the d ow ns tr ea m e nd in the movi ng  di re cti on of the do cumen t re ac he s  th e refer e nc e posi ti on  coi nci de s wit h di s app earance  timing o f a shad e.  T his ena bles the docu me nt end det ec tin g unit t o most r eliably detect the down s tream e ndin th e mo ving dire cti on ofa d o cument  based  on a  s had e appea r i ng  at  t he slot of t hebackme mber .
In th e document end det e cti ng unit of th e i nven t i on  it is pre fe r abl e that the detect ing meansde t ec ts appeara n ceti ming of  a shad e oft he down stream en d in themo ving d ire ction of t he docum ent and r e gards apoint  in  timewh enthe d ocumen t  ha s rel ativel ymoveda pre de termined  distance from a positi on the reofatthe detec ted app earance t imin g as timin g w hen  thedow n strea m en d  i n t h e mov ingd irectiono fthe d oc ument reach e s the  refe ren c e posi tion .
According to th e  invention, in  the d ocu men t  end  d etecting unit,  th ed e tectingme ans detects  timingwh e n the  downs treamend int h em ovingdire cti on of the  do cu m ent rea ch es the re fere nc e posi tion b a sedo n  only appearance  timi n g  of s h ade  of t he  downst r eamend in the  moving dir ection  ofthe d ocument .This s imp li fies the c o nstructio n for  detect in g asha de ofa do c u mentend,  s o t hat the e n t ir e  c on s tru ctio n ofth e do cument en d  detecti ngu nit issi mpl i f ied.
I n  t h e  documentend  dete c t ing unit o f  the in v entio n it i s pref erablet hat  t he colo r o f the surfa ce of the bac kmemb er and t he  inn er  wa ll  of the slot is  white;the ligh t - receiv ing mean s  is co mp osed of a pl urali ty of ligh t - rec eivinge lem ent s a rran ged  inp arallel to a direction w hich  is s u bst antia lly o rt hogonalt o th e moving direction ofthe document;
l i ght refl ect e dfr om the sl oto f the  bac k m embe r a nd l i g ht r e flec t ed  fro m thesurf ac eof the ba ck  member excl u din g th e slo t
 the_invention, the_document end detecting unit_detects a_shade_appearing at_the_slot of the_back member due_to an end of_a document, and_detects_either end of the document based on a result of detecting the shade. This_allows_appearance and_disappearance_of_a shade to be detected_with reliability, so that reliability_on detection_of either end of a document in the_document_end detecting unit_according to the invention is increased enough to be_more practicable than a conventional document_end detecting unit_which_uses_a back member having_no slot.
In the document end detecting_unit of the invention it is_preferable that the detecting means detects disappearance_timing of a shade of the_downstream end in the moving_direction of_the document and regards the_detected disappearance timing_as timing_when the downstream_end in the moving direction of_the document reaches_the reference position.
According to the invention,_in_the document end_detecting_unit,_the detecting_means regards a_detected_disappearance timing_of_a shade of a downstream end_in_the moving direction of a document as_timing when the end_reaches_the reference position. Timing_when the downstream end in_the moving direction of the document_reaches the_reference position_coincides with disappearance timing of a shade. This enables the document_end detecting unit to most reliably_detect the downstream end_in the_moving_direction of a_document_based on_a shade appearing at the slot of_the back_member.
In the document end detecting unit_of the invention it_is_preferable that the detecting means detects_appearance timing of a shade of_the downstream end in the_moving_direction_of the document and regards_a point in time when the_document has relatively_moved a predetermined distance from a position_thereof_at the detected appearance timing as_timing_when the downstream end in the_moving_direction_of the document reaches the_reference position.
According to the invention, in_the document end detecting unit, the detecting means detects_timing when the_downstream end in the moving_direction_of_the document reaches the reference position based on only appearance_timing of_shade of the_downstream end in the moving direction of the document. This_simplifies the construction for detecting a shade_of a document end, so that the entire construction of the_document end detecting unit is simplified.
In the document_end detecting unit of the invention it_is preferable that the_color_of the surface of the back member_and_the_inner_wall of the_slot is white;
the_light-receiving means is_composed of_a plurality of_light-receiving elements_arranged in parallel_to_a direction which is substantially orthogonal to the moving direction of the document;
light reflected from the slot of_the back member and light reflected_from the surface of the_back_member excluding the_slot