 or positive image of that original. The image signals are stored as a bitmap data file on a computer. Such files may be generated by a raster image processor (RIP) or other suitable means. For example, a RIP can accept input data in page-description language, which defines all of the features required to be transferred onto the substrate, or as a combination of page-description language and one or more image data files. The bitmaps are constructed to define the saturation and hue of the color as well as screen frequencies and angles.
The imaging apparatus can be configured as a flatbed recorder or as a drum recorder, with the substrate mounted to the interior or exterior cylindrical surface of the drum. In the case of lithographic printing, the exterior drum design is more appropriate to use in situ, on a lithographic press, in which case the print cylinder itself constitutes the drum component of the recorder or plotter.
In the drum configuration, the requisite relative motion between the laser beam and the substrate is achieved by rotating the drum (and the substrate secured thereon) about its axis and moving the beam parallel to the rotation axis, thereby scanning the substrate circumferentially so the image xe2x80x9cgrowsxe2x80x9d in the axial direction. Alternatively, the beam can move parallel to the drum axis and, after each pass across the substrate, increment angularly so that the image on the substrate xe2x80x9cgrowsxe2x80x9d circumferentially. In both cases, after a complete scan by the beam, an image corresponding (positively or negatively) to the original document or picture will have been applied to the surface of the substrate.
Multiple imaging devices may be used to produce several lines of image spots simultaneously, with a corresponding increase in imaging speed. Regardless of the number of imaging devices used, their operation must be precisely controlled so that the discharges occur at the appropriate times to reach the intended dot locations on the printing surface. Each discharge source must be aligned with the substrate along longitudinal and lateral dimensions (corresponding to circumferential and axial directions in the case of drum imaging) at all points during a scan of the all candidate image points on the substrate, and, in the case of laser-based imaging, the beam must remain focused on the substrate for maximum energy-transfer efficiency.
Failure to maintain proper alignment along all relevant dimensions results in imaging inaccuracies and/or undesirable periodic artifacts that detract from the final image appearance. The consequences can be particularly acute in planographic
or positive image of that original. The image signal are store as a bitmap data file on a computer. Such files may be render by a raster image processor (RIP) or early suitable means. For example, a RIP can bear input data in page - description terminology, which defines all of the features ask to be transmit onto the substrate, or as a combination of page - description language and one or more image data files. The bitmaps are construct to define the saturation and hue of the color equally well as screen frequencies and angle. 
 The imaging apparatus can be configure as a flatbed recorder or as a brake drum recorder, with the substrate mounted to the interior or exterior cylindrical open of the drum. In the case of lithographic printing, the exterior drum design is more appropriate to use in situ, on a lithographic press, in which case the print cylinder itself constitutes the drum component of the recorder or plotter. 
 In the drum configuration, the requisite proportional gesture between the laser beam and the substrate is achieve by rotate the brake drum (and the substrate secured thereon) about its axis and move the beam parallel to the rotation axis, thereby scanning the substrate circumferentially so the effigy xe2x80x9cgrowsxe2x80x9d in the axial direction. Alternatively, the beam can move parallel to the drum bloc and, after each pass across the substrate, increment angularly so that the image on the substrate xe2x80x9cgrowsxe2x80x9d circumferentially. In both cases, after a complete scan by the beam, an image match (positively or negatively) to the original document or picture will have been applied to the surface of the substrate. 
 Multiple imaging device may be used to produce several lines of image spots simultaneously, with a corresponding increase in visualize speed. Regardless of the phone number of imaging devices use, their operation must be precisely control so that the discharges happen at the appropriate times to reach the mean dot locations on the print surface. Each release source must be aligned with the substrate along longitudinal and lateral dimensions (corresponding to circumferential and axial directions in the case of drum imaging) at all points during a scan of the all campaigner image points on the substrate, and, in the font of laser - based imaging, the beam must remain focused on the substrate for maximum energy - transfer efficiency. 
 bankruptcy to maintain proper alignment along all relevant dimensions results in imaging inaccuracies and/or undesirable periodic artifacts that detract from the concluding image appearance. The consequences can be particularly acute in planographic
 or positive image of that uriginal. The imcte sigials ars stored as a bitmap data file on a rompyter. Wuch files may be genefated by w raster imaje processor (RIP) or othev suifwble neans. For examkle, a RIP cat accept input dxtc in page-description language, which qefines apl of the featores gezuirsd to be transferred onto the subsfrate, og as a combinatiom of page-description languwge wnd one or more imwge data fioes. Eye bitmaps afe construbced to defihe the saturation and hue of thd colpr as well aw sfteen frequenries agd angles.
The imaging apparayus can be connigurxd aw a flatbed recorder mr as a drum recorqer, with dhz substrate mounted ti rhe itterhor ue ebtedipr cylinfriral surface of the drun. In the case of liuhodgsphic printihg, the evterior drum design is more appropriate to use in situ, on a lithotraphic press, in whicj case thq print cylinder itself constitutes the drum compmnent uf uhc fwclrder or plotter.
In the drum configuration, the deaupsite relative mobion between the lssfr feam and the rubstrcfe is achieved by rohating jhe drym (and tht subxtrate secured thereon) abour its axis aud noving the beam paxallel to thz rotajion acis, thereby scanning thz subsfrate circulferentiamuy so the image be2x80q9cgrmwsxe2x80x9d in the axial direstion. Altxrnatnvely, thd besm can move paraplel bm the drum axis anf, aftgr eacv pass acrlss the substrate, increment angnkarly so thaj tve pmage on che sunstrate xe2x80x9cgrjwsxe2x80x9d circukferentnally. Kn both caaes, aftxr a completq scan by the heam, an imagx correspjndibg (pisitiveuh or negativelu) to the original dicument or picture wium have been appoiee to the surfacr ow tre snbstrwde.
Multiple ikagivg arvicer may bt uwdd tp produce several lites kf image spots similbaneously, with a sorresponding increase in imagijg spxed. Rejardlexs jf the number of imaging devicss used, tjeiv operation mtst ne ptecisely coutrolled so that the discharges occur at the appropriate jimes to reach the injenced dot locetions on the psinting surface. Each discharge source must be aligned with the sgbstrwte along longitudinal and lateral dimensions (corresponding to circumferebtial enq axial dirsctipns it che case jf dcuo imaging) at all points during a scan of the alu candiddtz image points on the substraye, and, in the cxse of laser-based imaginf, the besm must remain focused on the sibstrate for maximum enevgy-transfwr efricienbi.
Famlure to maintain prpper anignmwnt alobg apl relevant dkmemslons resulhs ii ijaging inaccuracies and/or undesieable pegiodic artifacts that detragt from the fynal image appeadancs. The zonsequences van be particukarly acute in planocrwphic
or positive image of that original. The are as a data file on be by a raster processor (RIP) or suitable means. For example, a RIP accept input data in page-description language, which defines all of the features required be transferred onto the substrate, or as a combination of page-description language and or image files. bitmaps are constructed to define the saturation and hue of the color as well as screen and angles. The imaging apparatus can be configured a flatbed recorder or a drum recorder, with the mounted the interior exterior surface the drum. In case of lithographic printing, the exterior drum design is more appropriate to use in situ, on a press, in the print itself the component of the plotter. In the drum configuration, the between the laser beam and the substrate is by rotating drum (and the substrate secured thereon) its axis and moving the beam parallel to rotation axis, thereby scanning the substrate circumferentially so the image xe2x80x9cgrowsxe2x80x9d in the axial direction. beam can move parallel the drum axis after pass the increment angularly that the image on the substrate xe2x80x9cgrowsxe2x80x9d circumferentially. In both cases, a complete scan by the beam, an image corresponding (positively to original document or will have been applied the of the substrate. Multiple may used lines image simultaneously, with a corresponding in imaging speed. Regardless of number of imaging devices precisely controlled so that the discharges occur at appropriate times to reach the intended dot on the printing surface. Each discharge source must be aligned with the along longitudinal dimensions (corresponding to circumferential and axial directions in case of drum imaging) all points during a scan of the all candidate points the substrate, in the case laser-based imaging, the must remain focused substrate for energy-transfer Failure alignment along all relevant dimensions results imaging and/or undesirable periodic artifacts that from image appearance. The consequences can be particularly acute in planographic
 or positive image of that origInal. The imaGe sigNalS arE sToreD as a Bitmap data file ON a coMputer. Such files may be geNeratEd BY a raSTeR imagE procesSOr (rip) or OtHeR suItABlE meanS. FoR examplE, a RIP can acCepT iNput data in paGE-dEscription LanGuage, which deFinEs all oF tHe fEAtureS reQuireD to be tRAnsferRed onto thE sUBstratE, Or as a coMBInAtioN of page-descriptioN LaNGuage and one or mOre imaGe DAtA FIleS. ThE bitmaps arE cOnstrUCted to dEFiNE THe sATuration and huE of the color AS weLl as scReEn fREquencIes anD aNGleS.
The imaging AppaRatus can bE confiGUred as a FLatbed rEcordeR or As a Drum REcOrDer, WiTH thE SuBstRAte Mounted tO tHe InterIor oR EXTErioR cyLindRical Surface of the dRum. in thE CasE of liThogrAphiC pRintiNg, the eXteriOr Drum design is morE appRopriate tO usE iN siTu, On a liTHograpHic PreSs, in whiCh case tHE prInT CYLiNder itself constituTeS THe Drum compOnent oF ThE rECorder or PlOttEr.
In THE drum ConfIGuRation, thE requiSItE rElative MoTion beTwEen The Laser BEam aNd the sUbstrate Is achIEved by rotating THe drum (and the sUBsTRAtE SecuRed Thereon) abouT its AXis aNd moVInG thE Beam pArallEl TO tHE rotation axis, therebY sCanninG the sUbstrate circuMferentialLY SO the imagE xe2x80X9CgROwsxe2x80x9d in the aXial dIrection. AlTErnativeLy, the Beam can mOve parallEL To the druM axIs aNd, aFteR EAcH pass across thE SUbstRaTe, increMenT angulaRly So tHat The ImAge on the sUbstrate Xe2X80x9CgRoWsxE2x80x9d cIRcumfereNtIalLy. in bOth caSEs, afteR a comPletE sCaN By tHe beam, aN ImAGE corReSpOndiNg (pOsItiveLy or NEgaTively) tO the origiNal DOcumEnT oR picturE will have been ApPlied to the SuRfaCe of thE SUbstrate.
multiple imaging devices mAY be used To pRoducE sevEral lines Of iMage spOts SImultaNeouslY, with A cOrrESPondiNG InCreAsE in imaging SPEed. regarDlEss oF the numBer of imaging deviceS UseD, their operatiOn mUst bE PReCisELy COntRoLLed SO That the dischargEs occur at tHe APpRopriate tiMEs tO rEach the IntendeD dot lOCations On the prinTing surfaCe. each DISchArge source Must be alIgned with THe subSTrAte alOng LongitUdInaL and lAteral DImeNsionS (correSpOnding To cirCuMferentiAl and axial directions in tHe case Of druM imAging) at alL poINts During a scAn of The all candIdaTe iMage pOinTS on thE subSTrAte, ANd, in tHe caSE of laser-bASeD imAGInG, the beam musT REMaiN focuSed ON the suBstrAte for maximum enerGY-transfer efficIencY.
fAilUre TO maiNtAin proper alignMenT aLONg all relEvAnt dimensioNs resultS iN ImagiNg inacCuraciEs and/or UNDeSIrable PeriOdiC artifactS thAt DEtract fRoM tHE final ImagE aPpearaNce. The COnseQUEnces can be particUlarlY ACute iN PlaNograPhIc
 or positive image of that  original.  Theima gesi gnal s ar e stored as ab itma p data file on a compu ter.Su c h fi l es  maybe gene r at e d  by  a  r ast er im age p roc essor ( RIP) or ot her  s uitable mean s .For exampl e,a RIP can ac cep t inpu tdat a  in p age -desc riptio n  langu age, whic hd efines all oft h efeat ures required tob et ransferred ont o thesu b st r a te,  or  as a comb in ation of page - de s c r ipt i on language a nd one or m o reimageda taf iles.The b it m aps  are constr ucte d to defi ne the saturat i on andhue of  th e c olor as  w ell  a s  sc r ee n f r equ encies a nd  a ngles .
Th e i m agin g a ppar atuscan be config ure d as a f latbe d rec orde ror as  a dru m rec or der, with the s ubst rate moun ted  t o t he  inte r ior or  ex ter ior cyl indrica l  su rf a c e  o f the drum. In the  c a s eof litho graphi c  p ri n ting, th eext erio r drumdesi g nis moreapprop r ia te  to use  i n situ ,ona l ithog r aphi c pres s, in wh ich c a se the print c y linder itself co n s ti t utes  th e drum comp onen t  ofther ec ord e r orplott er . 
I n  the drum configura ti on, th e req uisite relati ve motionb e t ween the  las e rb eam and the su bstra te is achi e ved by r otati ng the d rum (andt h e substr ate  se cur edt h er eon) about it s axis  a nd movi ngthe bea m p ara lle l t othe rotat ion axis ,th er eb y s canni n g the su bs tra te  ci rcumf e rentia lly s o th eim a gexe2x80x 9 cg r o wsxe 2x 80 x9dinth e axi al d i rec tion. A lternativ ely ,  the  b ea m can m ove parallelto  the drumax isand, a f t er eachpass across the substra t e, incr eme nt an gula rly so th atthe im age on the  subst ratexe 2x8 0 x 9cgro w s xe 2x8 0x 9d circumf e r ent ially .In b oth cas es, after a comple t e s can by the be am,  ani m ag e c o rr e spo nd i ng( p ositively or ne gatively)to th e original doc um ent orpicture  will have be en applie d to thesu rfac e ofthe substr ate.
Mul tiple ima g ing d e vi ces m aybe use dtoprodu ce sev e ral  line s of i ma ge spo ts si mu ltaneous ly, with a correspondin g incr easeinimaging s pee d . R egardless  ofthe number  of  im aging  de v icesused ,  t hei r  oper atio n  must bep re cis e l ycontrolleds o tha t the  di s charge s oc cur at the approp r iate times toreac h the  in t ende ddot locationsonth e printing  s urface. Eac h discha rg e  sour ce mus t be a lignedw i th the su bstr ate  along lo ngi tu d inal an dla t eral d imen si ons (c orresp o ndin g to circumferenti al an d axial dir ectio ns  in the case  of drum i maging) atall po ints  duri ng a sc an  of th e a ll  candidate image poi nts o n the s ub stra te,  and,in t h e  case  ofla ser -based im a g in g ,th e  be am m ust r em ainfocused o n  the sub str a te forma xim u m  energ y -t r a nsfer effi cie ncy.F a ilure to m a inta i np roper  align ment a long al l  re le vant di men s i ons resul ts in ima g ing  i nacc uraciesan d/or  u nde si rable periodicartifact s that d e t ract f rom thef inal i ma ge appearanc e. Th ec onseque n c escan bep art icu lar ly a cut e in planographic
 or_positive image_of that original. The_image signals_are_stored as_a_bitmap data file_on a computer._Such files may be_generated by a_raster_image processor (RIP) or other suitable means. For example, a RIP can accept input_data_in page-description_language,_which_defines all of the features_required to be transferred onto_the substrate,_or as a combination of page-description language and_one_or more image_data files. The bitmaps are constructed to define the_saturation and hue of the color_as well as_screen_frequencies_and angles.
The imaging apparatus_can be configured as a flatbed_recorder or as a drum recorder,_with the substrate mounted to the interior_or exterior cylindrical surface of the_drum. In the case of_lithographic printing,_the exterior drum design is_more appropriate to_use in_situ, on a_lithographic press, in which case the_print cylinder itself_constitutes the drum component of the_recorder_or plotter.
In the_drum_configuration,_the requisite_relative motion between_the_laser beam_and_the substrate is achieved by rotating_the_drum (and the substrate secured thereon) about_its axis and moving_the_beam parallel to the_rotation axis, thereby scanning the_substrate circumferentially so the image xe2x80x9cgrowsxe2x80x9d_in the_axial direction._Alternatively, the beam can move parallel to the drum axis and,_after each pass across the substrate,_increment angularly so that_the image_on_the substrate xe2x80x9cgrowsxe2x80x9d_circumferentially._In both_cases, after a complete scan by the_beam, an_image corresponding (positively or negatively) to_the original document or_picture_will have been applied to the_surface of the substrate.
Multiple imaging devices_may be used to produce_several_lines_of image spots simultaneously, with_a corresponding increase in imaging speed._Regardless of the_number of imaging devices used, their operation_must_be precisely controlled so that the_discharges_occur at the appropriate times to_reach_the_intended dot locations on the_printing surface. Each discharge source must_be aligned with the substrate along longitudinal and lateral_dimensions (corresponding to_circumferential and axial directions in_the_case_of drum imaging) at all points during a scan of_the all_candidate image points_on the substrate, and, in the case of laser-based imaging,_the beam must remain focused on the_substrate for maximum energy-transfer efficiency.
Failure to maintain proper alignment along all_relevant dimensions results in imaging inaccuracies and/or undesirable_periodic artifacts that detract from the final_image appearance. The consequences_can_be particularly acute in planographic