Rampal, V V

IACS Institutional Repository

lndian J. Phfp. 486-470 (1080) Laser application in weapon guidance aDd active imaging V V Ra.mpal* Inatrwnent. BeeeaNh and Development Establishment, Debra Dun An importlltnt phllillll of LI1I8or IIopplica.tion for Dofllllce purposes ha.s boen in the gllidllolloe of. WllapOD/! whereb;y tho object to bo destroyed is Jllumina1;od hy tILe llloBai' ta~ion and the wllllopon is homed onto the targot a.long tho diroctiol~ of sClIotterod radi!Wtion. The dllv(llopmant ~tlltrtod 1ll the lato sixties and practioal deviooa oa.lled tho Smart bombs hlllVe beon in opera.tIon in th" lOoter phBoSo of Vietnllom Wa,T (Verble 1974). Though cOIllihlora,ble dovolopment hilts tWi:tln plUtco since thon, lo~ of mOllUY o.nd effort U! still boing put in to extend th .. o .. po.-bilities of theso systems l'h .. high lIooour .. oy of IItttack and ovuro.ll oost effoctive-nellS mako tho sylltem of Laser dosignatIon wurthy of serious oonsidoratiOll. Modem low :flying o.il'crllofts usod for ground .. V.l\Ck are now fitted with sUItable L .. sor instrumont .. tion to provido (110) rango findmg o,nd t .. rget designation capllo-bilitios for saoktng the targot, (b) moMuring its Tango and sondIng the woapon ontu it, thereby reducing tho human olement to tho minimum. Recently 10·6 mloron radiation hb.s b(,Uh uaud ttl imprbl'o the capabiJi~y of tho syijtem under IIotluospheric conditions of fog. smoke, hazo utc. (Taylor 1977, Rudko 1977). One of the most rocent IIopplioatil)JIs Ill' LOosor for Defllnon ha.s appollored in the fiold of active im~ing. FoJluwlllg the developmunt of LlIoSor Scannors (Phela.lI 1971, Roiuho 1975) Lasor btlo.mK h .. vllnuw boon usoo for nna{!iJ1& diHtaut target,a dudng dlloY and night (Arapov 1975). Both CW a,nd pulaed rlldiation oan btl uRed. Imago clltn eithor bo photographed (Neumann 1965) or storod hi tho form of olootrio .. l pulses and displayed Bot WIll. Suitable SIgnal processing oan bo omployed for improving tho image or extraotion of informo.tion rogo.rding tho rllougo and depth of tho target. Using high powor ropetdave pulsed lasor, imagbs of distant targets upto 110 fow km can bo stored or viewed in roal ti)JIl!I. Infro'I'(ld IIM!II1:fI Bot 1·06 micron or 10·6 micron can bs USed (Soulf 1975, Courtonay 1976, Lamborts 1076). Tho systom~ hd.ve bool1 demonstraWd il~ laboratories and tho 8ovt¥lllobillty of pl'a.otioal devioes for fiald Use ia imminont. Laser lJaidallC. Tho prilloiplo of la.811r glllda.noe is illulltra.tod in Figuro 1. ~e. target seleoted with the holp of u,ti optical sight is illuminlloted With the radiatIOn from 110 laser • NbW at Defonoe EleobmDiOl AppliaatioJle Laboratory, Baipur Boad, Del1ta DIIIl·.'8UOI. 465 27 466 V V Rampal TAI!IT Figure 1. ne.igwltion of target by LBIIOr Illumination. Bouma which may bo a high f'Op. ratu 'pulsed NdYAG or a 10·(l micron TEA COa la.sor. Tlltl aroa. sl-llaotivuly lllummatud by the 1,00,111 doos not oxuood Dna or two squau'o motors tor l'a.ng<lH upto RovlIrai ktl,,'ueturs SO tlu,t. tho targot is porfoetly UUSigllllotud. When th ... targut is illllmina.tod it Of{ilCti vely bncomos itsolf 0, SOUr(JO ra.uiating in Iloll dir6ctlOns. This scllottcrcu 1'Ilodiatioll Ill'OviuCH t,o tho rO(1oivor tho mformllotion that is roqm/'ud fOI looating tho targut and guidaueu of wcapt'll on it. Tho rO(JuivOI Ip~H a qUllclra.nt typo of dllt.,etol' (FiguTo 2) ill which tlw Ullbalu.ncu curnmt from opposito quadfl~nt~ provides tho ~un80 of dimctioll in which tho radiation is coming to tho rocoivo)'. Tho dotuctor output, is couphl to 110 closuu. 1001) servo ,~yijtom which brings tho dctector in lino wit,h tho diroc. tion of J'cooivod ru,(liation 80 110M to hring a null. In this position tho apot. of recoivod r11odlation filIR equaJ.ly all tho four qlladralltH and tho r(Jooivl1/' points in t.ho direc-tion of tho targot. Through tho use of flon intorferonco filtor the raceiver is mado sonsltivo to only t.llH laqur wavolongth, thus cutting out tho baokground lind ma.king tho detoction of to.rgot possible both dnring day and night. Tho 11\~or illumina.tol' is gonorally a high rop. ratu pulsed la,s[H' SOUT<'O in till) infmrod which sonds tho Ia~ur radiation onto tho tllorgot. Tho Rolection of ta,rgot is dOllo by a. viowing tolorioopo which form~ 1\ pllort of the illumilla.tor. Ono such Laser application in weapon guidance "f .-J ofP~ lo..J spar NOt nNJRAL''j(&' Y'" Dur PUTS~ (_I SPlIT C~J. 811T"·kS ... • DU1 Purs %.IRD Figure 2. Direotion sensing by Quadrant Detaotor. 467 o,rrangomont is shuwn in Figure 3. Depending on tho particulo,r requiroment oftho guida.noo system dosired, tho illuminator lla.n he (lithor (a) ground mOllnted, (b) ha.lld holu by the porson proceoding ahollod for tho selection of target, (e) pla.ced in th~ attacking aircro,ft or (d) mountoo in thE> remotely piloted vohicle (RPV). 0 ....... IN ...... Figure 8. Block diagrlWl of Las.r Ilhunina.ticn. Tho dotection SydtlllU that BOO],S tho tllorgot cllon either bo (a) Sllllplo duoot VlllW toloscope system, (L) (lirect view infrared systom llsing image intonHifier tubu or (u) low light lov"l TV systom. Tltis deteotion system fOIlllS an integral Pllort of the servo luup that gUldus tho dirllction of the woapun onto tho ta.rget. The guidod weapons Clloll ~ither be (a.) glillo bombs i.o , frou falling grllovity bomb~ o[ (b) mi~>liles or (0) a.rtillory projecti\llK. The las",r guidllollcll of missiles lIoud arty. projectiles 011011 bo dono by oithor of tho throe wOoys illustrated in Flgl~l'll 4. Tho choico of pa.rtwula.r Hystom deponds upon the conditions prevailing !lot tho tim(l. 8mce those wCllopons a.re vory fa.st moving, a, quick Ilo\)ting sensing and oontrol mechanism is required for guidanoe. o D ____ ----... ~ .----_.-- ~ O ----... ----. .. (b) liliiii AT '1'111 SAIIf _ (t)~ ~t!i~ ~ ~FipI'e 4. Methods of guidance of miB8iJ.eoj and projelltnes. In conaidotlng the cost effeotiveil.ess of laBor guided woapon A stom it is to bo lemembc!rod that tJlc seeker and oontrol sypi;om which iM added onto tho weapon also gets dostroy6lj alongWlth tho wea.pon. ThorafolO tho wua.pon cOBt increases. But still if tho numbuf of woapons and numbor of tJials reqUlfud to dtlstr oy a. pa.rtioula.r ta.rgot is takon iuto acoount the ovoro.l1 oost offoetivoullBS is found to bo ill f!lovour of tho lllo80r guiJod system. In thIS COllnuctlOn following points are rolevant: (a) pm pointed ta.rgots IUO destroyod IIond ovon illrgllts in I'opuiatt'd Ilroa~ can be o.ttcmptud-&ocuracitts of 5-10 motors aru acllleVlld. (b) First round hit is aimost IIossurod a.n!l thorofore lossur No. of bombs b IIoVO to be UIlOd. This rlJdutJes tho cost dUe to tranKportu.tioll o.nd stora.go of tho heavy bombs m the battle o,roa. (e) Losser number of attempts by tho bomber hBvo to bo mado so tha~ tho lisk illvolvod in tho d9s~ructioll of tho aottBooidl1g aircraft is roducod. Laser imalliag AJ' oarly as 1965 it was puintl1d out tho,t u.sing a gia.nt pultied ldoso.r for illuminat· ing a, target fur pb.otdgraphy hag certain advanta.ge8; tho OXPOBllJO of the Damar .. oo,n bo for a vory lIhoH time (30-50 lis, oorrosponding Lo the iMer pulse duration) and tha.t this axpo/IDl"c ban bo delayed by a known amount thus reduoing the baok sca.~ter. Also knowiodge of the S,djl1Sto,blo known dolOlY givils information about the raongo of tho targot. ThiB is IIop~rt from tho flMlt that MilO second exposuro of the object ra1nMns alnioRt Ill1detucted. by tho o\.Jject p&rtiuul~ly ""hen infr~"d lllllar ilIusod. Also ull~ of intorforcnoe filter at thtl laser WIIoVo]lJngtb uns,bloB the operation hoLIi duribg day and n.lgbt. Laser application in weapon guidance 469 Ra.ngo gatod ph()tog"~phy W8R first done by usiug iI Q-switohcd ruby 1 ..... 0l' (Noltm31l1l 1965), A doclId .. 1l>tOJ', " ~imi!Qr oxpurimnnt was purfnrlllt\d l,y 1lIung ~ Nd gla.s8 I".,er· a.t 1,06 miorun (Arapov 1975), For rallson. of lo~~ tio",ttoJ'ing, mfr",red In.sUl IS ~roful'",bl~ u.nd J lingo gath'g L''''hlliquos ('«'iguru u) illcr"",sUS ,he Oontrllo8t of tlw VlCwud oblect bo"~uso IIf reiluotion In back BUllotturillll i1'tunsity, !MMlNI ,rnes ~4i'­.lIII!.la -FlguJ't! 5, Range gated imaging by Loser D1umiaatiOl1, A ropotltivoJy ]luLled TEA CO, lllollllJ.' has buon ullCd r"cuntly to imago ~n objoot l.y suudming (Cllurtcnuy 1976). A sorvll controlled giJnh",lIool muror pn~itiol1<"l on tho laser axi~ iH IIROd to ilim the I'llui",tion a.t Uk. tlloJ gut, The boam ill advanced by RWIIoU anglll"r 8tup,~ ill ~imllth o,n,l &1, olloh sueoos.sive poJlition " lu,sel' pulse i~ OlU'ttl~l. At th" eud of II> horizontal Jinp. the I'Ram is d"prl,s~"d by a. Hm~I1 lingle aLIi! th"l1 Rtoppoll bo.ck llorOH~ thA targ!lt ~C"llo A ma.trix I.f 32 X 240 pOUlt~ in tho ta.rget aOOllt1 arc thUB illummRtutl In BUcooSHion, 'Bocauso tho prf is 1 ppH tho signllol rtltum from ollob pulse trllusmission is stored, 'Cllis m'l~hotl of imaging llo11ow~ signal procoBsmg to bo done in <ll'<ior to itnl'l'Cve the qua.lity of tho low I'OBolutiul1 (ap'ltiIlJ) image by modIfying tho intuuaJLy profilA of oaoh pioturo ololUont to pro<llluo grlly Bca.lo interpolation botwoon IIdjllaont "lemont!, Thiil ma.kes object ol'llior to ruoognise, (Jilin!', htgh avorage llOwer Nd YAG laosor ... loug ra.ngo im~ging system basod on direot tloteut.\on of s"~tturod l",sor light from a. lasor ~ca,nnool oJ,joct has 1.011011 dllmonstr",to,l (L~mborts 1976), A Q-swituhod 11>801' opora.ting II~ 25 KHz prf ill UM<l(1 with 'Il "Jill Y sClllluing mirrors opor80ting lit 100 Hz and 2 Hz roapeotivuly. The output bellm 11< 2-5 em III dis and tho object is vieWed with lin aiming taw· soope fixod lllong.ido tho 10.901' trllonBmi~ter, Tho doLoction system URes II largo IIPloriuro F1'68nl Ions wit./! 1 em 0118 photoctiodo YAG 444, Au illtorfllfonce 1l.1tor is used b6[01'0 the detootor to cut (lown tJie ba.ok ground, Tho J'('SCilltioll of the system is datllrminod, by the dlvergonco of tho sca.nning Ia.ser bolllD Ilnd 28 4: 70 V V Rampal tho sOnBi~ivity is determined, alIlong other tbi:D,g's, by tho dia. of the recoiver aperture. TIle detooted video is first IIolIlplifiod a.nd thon passed through ga.ting eloctronics. Both the delay and gating timo oan he adjustod. A tm alIlplifier provides 110 tilIle vllotiable gllin to cOlIlpenslIte the R" dependanoe of tho reHeated la,~tlr power. The displllY is obtained by intensity modulation of CRT Ilolld a TV like imllge of the object is obta.ined. Tho results ~how that it is possiblo to get good rllongegllotcd imagos of targets upto 1·5 lon. The 11.180r ima.ging systems dosoribod abovo have given oredanoe to the pOSllibihty of using high rop. ra.te puwed lasor for illumina.tion, Bond COnBequ6Xlt imaging, of distant Largcts, partiouliuly at night, when considorations of ObjlCt distanue IIond imago qUllolity mako tho u~e of pllssivtl hight viewing. using imago intensifier tubos (II 'l'ube) rllother limited. Tho UBO of II Tubos is restticted to the night viewing condition. The ll.lser Bellnued imllging on the oth~i hllnd cllon be offected both during dllY lind night by tho uso of interforence Iter. Also thoro is acopo of el~otronic Bignal processing of tho scanned ima.ge n ordor to extrllct tho dosired infol'mation from the 16etlivCll ima.ge, and tllis ea be clone almost in tho roal time domalll. l!luther, when performod in dl'sertl onviron-ment, whoro problem of shimmoring and refra.ctivo index varilltion with spa('" Bond time IIor6 presont, this mAthod is likely to giv(, b~tter results. This is bocllu~1l the time of oJ!!posure is ao sma.ll thllot tho motlium is almost frozen in timo for each observa.tion. ThtJI"uforo the smollring offoct on the image, observed whon viowed on OW ba.sis, is likoly to ho eonRidorably roduced. In oonclusion, 1,Iw imporLanoe of lllser illuminatioll of II ~lIorgot, for its imag-ing, !lond guidanoe of weapons onto it, hll8 bmm duly recognisod du.ring the last doca.dtl. Systems hllv(l been demonstrated with potcntilll a.dva,nta,go~ aud devolopment is ill progroRli for further improvemont of the instrumontlltion involvod. Though both the field~ of laBor imlloging lind lasor gl1ida.nco arB impor-tant to the Defence Stlctor, the IIoctive ima.ging of objocts by IIloBor illumina.Lioll is equa.lly signi£.Ga.nl, to tho pea.uo time uSers. Reference. Arapov A P, Arpishkin V H, Inyuslrin A I, Mur .. tov V R, Spiprukov V X, St.panov A E, and Stepanov V H 1975 Boo. J. Opt. TechTlf}!. 42289 Courtenoy T H, Boulier J F and Hen.hall H 1976 I",rarer/, PfwU.ica 16 95 Lambert. C W 1976 Applied Opeics 15 1284 Neumann D B 1965 Jr. BMP:I.'IJi 74 313 Phelan R J Jr and Meo N L Jr 1971 Applied Opt. 10858 Reiche Von S 1973 Optik 3750 Budko R I, Bami. J W and Banak E 1977 IliJliJliJ Jr. Quant. l!Jloct,ronic QE.13 39D Boulf C N 1975 Proo. SPIliJ 67 13 Taylor M J, DaVlOB P H Iilld Brown D W 1977 IliJEE Jr. Quant. EleDtr. qE.13 3aD Verble X E and MaJ.vem C J 1974 Int. DB!. Rev. 2204 

Laser Application in Weapon Guidance and Active Imaging

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Laser Application in Weapon Guidance and Active Imaging

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