......------------~~---~- --

Intern~tional'Cöuccil!orthe Exploration cf tee Sca/.

co ••-,. 1.1his papör nt)t tD CH ~i'tcd \::ithout.-..!?1:ioI' reler':.'!nce tc tt~e antu<.","";,_.

eH 1976/B:21 .Gear &De~~viou: cttce

, . b"":, ..

c S W~rdle ~~d RPriestley'M~riue Ia~~rat6rj

Abcrdeen'., .

-1:HE 1:3ASIc.rn:rimIPLES OF.: eiosEr> cmCU"ri 'l'EIEimIO~j SYS!DtS

:Fort ,i,\OORAToRY. /UID 'p'riu> .usi;n. Fi:SImÜ~ k~~faCH.. .

.'

(Presentcd ~tJoint Tecb.."lical Sp.....~ion' leES: vioridng G.rOUPt 'Hull ~ UK; ~..o .~'Mar~h 1976,' lIobr.ervi'ng methods B't· sen ror fish 'and gear")~: '

Iiitröduction

'The~iübe~ uaed in:televlciion'ca~eras'nre'conttnuaI1Ybeing deve16ped andrecently, same advnnces 'bAv~ :been mhdo' \;hich are of' grc.'J.t:·!rril'ort.1nco to I::Ilrinencientißta: . Thc normäl·ilntirilotiy·tri5ulphide·~ vidicon tuoe- (/u1on1968)

,:co~oDly t,iupplied.' i12:·ourveilla.nce cameras'wlls, evolve'd bCCil'J.SC'of its. good pancbromtic'properties,' tb3t is, it tilrncd a bcü.cmced coloUred .

BCino, prOper17:illU:inatod~·into·an exP~ctcd black and whito,imnge'with'iin expected' contrzWt: range~. Tbe scientist -working with',li~e' fiah in,:'aquarii, or'3O mdeep,in ·the sea', !illc'iS tM.t this tYPe o! c8.D2em .does not 'work~at all weIl unlecs·bright daylight:il1~ination,ißused; ~hich ver,y örten .diGturba 'tho behav!oUr cf th'etish nnd invalidates the ~Ä1'e:d6cnt.· 'I'he

·prC;blcms ol recordlng Witli :rum in· fisheries research were tlefined by, .'I;Ien=ings (1972), who'related the propertiea of' trat1S:Iiiesion of light by the\,(ater to the ehS.racters inherent iil thc!" film emulsions. ThefH~ basicpropertieaof'light,' dcneribed an~'illustratedby Reocmirigs, (1972), apply',also to ~elerision used in ,',the ,5eb.~The target in the vidicon TV tube andthc phctocathoda.'.iD,th~'intel'!-Gifie~ TV tube cor!'asl'0nd t~~h~' emulsion. ..'un~ in fUm:eameras... Tlie specific propertiesof the tarset.s and photoeathodesuoed in~tcreviäicn camerus var.r. !rem the ~~ncbrömatic nntimony.triaUlphide.target,~entionednbove, to the mnny special F~pose targets an1 photoeathodes 'each with its o~n ch~cteristic Specträl sensitiTlty and otherdjnamicprcporties. <ScbleCki and \la:njUer1972). Recently devclopmentor the .silicon ~iode umy target (Wool~,a~d J!en.'lett ~ 19(0), MS led to cameraawill aili ted tc', tll:0··lement' nnalYBis~ u~ing' red and inrra-red light i relevant inaq,uari;m"behaViour studi~ß.'The- "änieeamera' tube \l1th'an llssociated photo­c!'.th9de:intensificrr (RCA' eleetronic' compdnents,' 4804 camera' tuba. family) h:isgiven: an· id'e'al 'camern-' ~or lmderwatEll~~' obsemtion, usiilg tbe naturBl gre~nilluminatiön in'the 'see. down to, .a' pl·~ctical1.ow lig.l-,.t level.· .. Other priiiciplesöl television,ciu'be exploited by:th~acienti~t ~kinguGe or,co~~erciällyavo.ilall;te tö!levlsion npV:1rntus' and. the Prescnt !,oper attcmpts to outliile' themore'r~lQvant:~ropertieaci! clo?cd circurt televiGi~n 6ystems~

.,!ha norma1.'· CCTI/' 51stem

:The bUeic.clQscd·eircutt teievi~i~n system commercial1y cuFPlied as asurveUlancesyatem, uses ä. calncrli'to forr.l ü ·~tandaI"d c:odcd television iragecf anöbäcrved ouject'and passe.e tha ntandard cciQedv~ve form, via a c&ble,to'ti telefision moriitör,which accurately'decodesl:he electronic wave form.and:preccnts an,imase oftheobject ,to ün.obGerver~ :A permanent record'o!thi'ff" image COOl be t!a~e ,byrecording simultaneously tee coc1ed wavc form usiiigä ,video' tape recorder. The S3!l1~' scene' rccorded. 'on tape can then be replsyedvta,thomonitor immedintc~Y"orat any ether time, and can:be easily eopicd•.,

L 1

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..Sö~e' video tape equip::ient 'ia designed, so tlurt the scene cun ce replayedfra.moby frame~ thuo allo\dng careftil ?.7JA1ysis ci! :::ovement etc•.. For 'inov~mezit

~~ysis the..inscr~i~n.o~ r.n.a:::9.\irc.te ~U~tal clock, int!J ..tbe video taperccord a110w3 eXact·tir.ting·of-evo'i:y frame; .Tl-.:o'ditfcrent views"of thc Same­sub.iect can.be cQmbin~d..b:r.a.,mi~ipg·w;iton one,Q~ tl'N :fi:~r;;co,' or th~ silte

- di~tal clock C<ln be 'added. to (ach of:the.aynchronise-d ianges tl.nd. these ,canbe recorded separetely on two video tape reccrdcr3~. Thapossibilities foran8.lysis~ or illustrative purposes.; using t,elevision, are numt:roun;; .

• •.. , t.

'!he.television wa"lefor:u'-- ..._-- .

The, at.nndard closeet circuit TV picbre ia .trans!ornied to an electric~ wavt:pattern .in the ce.merä. tub.e~ ... t'eing, t~s 925. ;Linetelevisiön. cy~te6.C0m:::1oli'+7·uaed in Eurcl'e witli a 50 Hz niaiila frequmlcy, .the irlage fi~ld cD. th.e.TY ~ubeisscanned 5Ot1mcB,per seeond.The ttmetaken by the.eleetron b~aQ tosean' ,the tube (eamora arid monitor) is18~4·ms änd the beam returns.to.thQ,~tartoftha. iieit seM. dliriIig 1.6 ins.; The beam crosses the imäge ficld 'oltring -the·18~4msin,287.5:.parallel hOl'i::::ntal: lines.and.:~len re,turiis,.t9.the·'Btnr~.~f,~~etl~xt,

. ~. _.6~n~urinc' ~~e. ~ilj2~_ for 25 Jincs' .~]\actly_., ~e .. stprt. oi' each lino,. nenn ,i~ .sePa:rated 1?Y:6~ lUG•.: . The ,p~si~iQri: of. thc. Pj.cturf: i6 JrA;nt~jneo bS .t~?accurate ti:ning' 0.1' ,.the.~line and fi~ld scan b:Cg. G".rrichronised· pulse. generator.~ote tba,.t::~a~h f~c;td:l~u;;t.8.20, cis or ?O,<JpOJus;, 'f}.~C~ liJ?e lnats. 6!~l!3{ .t.1~~ear~ there!o;,e:i!l'prac~ice }12.5li~cs per.. 1"iel~. ?5,~r(r~Wt.t?l?nned.,:.~~e

c01nplete TV~'frar:~:is'~~chD.ica.l.ly acbiey~d by 2 ;;c~. o;t.ightly~di13placci4 {+o th3.t. the·J.ines intcrlace in ~lt:erna~,~··field.s~ns,~vi!lZ r,ise to :the;625 l~~ .:framewlwre, in, tac t ,50 lj.ncsare not: ßca~ed l~vil1g 575 lint?n.:~ .9,~p.e~ line standardshave.n SimilAr.liJ.sic. fom.;.: For, urialj~ic~l:work where siriglo fi.cld8 are '. ,relovaxit,.it, in imporb#t to roo.li6~, tluit:+1 singl.e. usabl~.pictur~ is li:#~~dto on11 :287.5:.line~.on 0:925 lirie c;Yate:i1.' ~ 11: shou:td also. bc realised t~la.ttlie spot 1145 ä. .ccnritait diameter i.o...o. monitor 9.r Cürn~ra, anc1..a liDe ron ~nlyfiuctuate in, brightness.and-cannot ...be cplit 10ngi~.udinal1y.,ai::dso verticnlresolütionoo is,licih1d, to 28?...5,.horizontal'liueß on wiy Gingle field.' It··shoU1~ als~ ~ b~ ,noted. ~'hat ..thc!. te1-~vis~onc::iincrD., has n.o ohut~,~·· arid;1igbt:"..~.,arrives on,.the· front of the 'camera tu}·, it an· timeo 50. that thu. image., .picked up,'by: ~he.· 6;~n reaUJ,ts from',tiie ,ccUm~atiön o.r,li~t· 9~i;1g 1/50:· öt,

, . n scco!ld•.

'nie, camera·

'. The·,:imäge.in~.the:cacer~·'i~.·:f~~C!.d.op~ic..ü1Yby.i Gui,b.ble'lez:t~ 'IIh$.~h'foc~sseB. the: imag{t ·of· the, object. thrc_ugh~ tlle: cnd...:w.indo~ ~t:. t!le, camem. tube

, Qri·,t~ ·,!:he sensitive targe.t eurfc:ü:e."\",.~:Tbe:.-9.ualitj.. or...~hi6 foc'lJ,ssc.d" i~.ag~ is,dependent on tha,lcllf.l and just as in fi1.Cl..camcras the umount~01' liGht:.depth or, focus·,a:nd. ii:1age quality, ar~- dependent ~ni th~ f.1p'crture oi. ;tbo,lens.· "There urö variouG aiies· ,of end windov 01' television CaUlera. tub~s

'.,~ngi~o .from:i!I1uP.tc) 1~1:~f:· ,'l\ibe,Win~9ws~~rc ,circular,~!i:Fhe'wi'iidO,,!": .diameter. is therefore rel'at'p.d.. tothe..MXw\imdiigonal' t}-oAt-.can. hc fitted intotbc circle ror äzi image' "r'ectanglu' witll' sine~' in' tlie' rc.Üo·,3:l.~· ,An i~ierectangle with units 3 by ,l+fits n, circle having.5 tinits cf.diameter.;,. It -isiMporttmt, to have a lenG designedto pt-oject än imtlse' ·with· a' dÜlt'leter' cf ätleast that of the cndwindow of the ~m~ra tubewhan the objcct i~ ~t infinity.,~is 16 rior~liy 5pccifi~d'.a:s the:.i~6~'·P'r"ojcct,ion anglE; o'r the' iriiäg'e, "',, mxinn~, fi~ld si~.o~: tro~~ \:t,~le:.:h:io.l1. C'..araeraG are fitt~d,with :i. tCInO\U1~, 'this

aimply indic::at.ec til."lt .the,.lens wil,l·.fit.:the c. moupt thread und the·.!oclismarkings engravcd onthe lens mount should havc, Dome meanini;: ~\'"C.rn6u..'1t

..1enswUl not, nece3i"irily.· sene:i-at~,.~ccuräl;e ~m.1.ßes on t.\ 1~fl end ~indo~.:' ..16,rw:lcino.film carric.s.i~n.iin?ge.with a 12..mm diagoml. ,16.I!l:1, filt1.e.::ttner!i'tenues :ire. thercfor~ ,only de6igned for ueß ",h~rc' it"~Gc field~ "arG %16. möre._,~bnJi ~" or 12 Cltl in di.."\meter; '1'0 avoid 105s o·! tnll.X'ginaJ. rcsolution selection

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. of the ~c~rec~'l~no ~ill boccne p;rtic~arly,i~örta.~t whcn .USiDb TI" ~im~ras. :fittedwithtuof,'.l with'a·target l.'lrSer'th:mJ-u, (12 rmn), diameter:. This, '. =.

.~arginaJ. detcrioration'cau~ed by.uning,unsuitable lenseo c~n bccome particulnrly,..notic~a,ble \lith 'widcariglä:~e,nsQswith' short, fbcal'lengtliß. . . .

....

, '..

"

.fueB. cf e~mer<i. tube . :',

': -The v~(:iicon 'tube ~iit'h an' ~nt'iriony: tri;~phide target b8.'~,b'ec~ uo~d. ..in thci"~Ujority or 5urvcilJ.an~e carnc!-lis;', !ntroduccd.in·1954 it.ol1o'Wcd the ,dcsi~;n

of sro.."Ül 'cQn-geni~nt 'IV ca::lcl'll.!;. Thc\!Ord Hvidiconll , describes the :f<lrticclar. . electrönic'. methcd'. cf':c'ollcctin~ the" p:i..chire ",'3.'l'O form froci, tho. fZice 6f. thc ..

tube, alt~rriätiv~ me~hods:are-o.eacribcd .by th'e. words:.J'orthicc;mtl. aad tlicocou";o • In: all TV: c.:i:noro.s t.hl.~ 'preci'1lo1y ccntl':ol1.ed' elcctronic bC~!ll SC~l.US,the ir;:.::tge.' a.-rca of the, target 'tl~ deöcribed. u.ndt;r' w:;i:l1c'· fOl.'rn, ar,o~·e. Th;;: tm'get in: tue. ', . b.orina1·'v'idicou ,is .. n;;idc ,a! ma7ly. POJ.YOl':'I~taJJ.i.ne layero ·oi.,.a.ntimc;mr. trisUlpnide.',: An' illumiriated: öbject .fcicuSsed· asan·:image: on .this.,to.rget: üep;Lc:teri zoii~s .o,! .... electroris,:, th~:der;ree'of ·depletio~.depepding ott:the. inten'sity cf ,the l~ght•

.. ' eile iniportan\;·J;:Iropei·tJ" of D.pcl:r~ryctnllina tnrr~et. reatt;rjn) ,ir; ,t? l:cop thiu'. .. ,·?epl'eted.. z~~e;, llu:'..nt:i,tat;ivfl'tmd ;precie-~'{lad 'not nllQW.l?-ter.41· lr.o·..er:lt:l,t .:~i'::> ._ ne1ghbottring eloctron5: un-:il· this ZOllO is ..~ef'i.l~~d.: l);;~ t.hEt nCftuning clcctron'

• " .,' bcam.'·T'tle; bet'.m· of: el~ctröi)s i:s :·8can.~od o;ler .tl'le, irJal3e·t~ri-i aZId ~;cnSt;S .. ~. " :,;zones satur:J.t'cd·~~itli t'.l€'ctrons '(darlt .area~) .a.ndzcr.eo..depleteJ. of: c:lect.ro;1:i. ' .. ' (vell:J.itC'.l·e~o)\·thc lioletJ.are thus,r;jfillcd 'by the,sc~r.ning 1.:ca~l~, The. ," . "cMnging current:' in' thc Eolectron beac' cause:d b~' thu crOz.singof' full <:.na

'emptyhol~s is dotcct~c by a ,conductiu6 layer in contact'with tl~,t~set,wlrichdctccts chane;c~; in ciirrent; ", '~'l:ic~o .-changcri ar~ ted d u'cc!:ly to b.. -,tineo . ...

. ampli:ri~r close to the front, end or the tube~ Thc voltl:t!p pat.t~rl1s originating. ,: 'as' c\U'renl:; cha."lges in. th~ elcctron. .lH:~o.ta l.l.re linl:cd to tue, field etnd l.ine timing

" ',' . '.. ,:~' pulses origin..'J.tiri~,ix'om- .thl~ ßyllc.hionisocl pull:ie generator. fL.'1d ~: co;npcsi te ,,:rive'. .' .' - form is tliua proc en~c:d and 1;::1G~;ed froi:i tlte .6t.mera. , Tha ~lord..,id'teon r Eifers ... _', to .this mcthoclcf tr,ihcfE:i'ring the clQt.:tronhole pattern into :=on elcctronic'.. \fave form. The orth.icon ,method is to collr3ct: thl} brolil. reilech,:d' frani the.. :....... target' lind ",oal{(l U::l~, Qf .the· !at:;t '~liat the !'eflcott-:d be.:,m i 6 sb6rt 'of ,, .' .' ~lectron5'\-Jhen' filling electron holes nud' rieb in' eloctt;onu \.;!lr-n reflectcd

" ' f'roDi dark areas.· In. t'hc 'isoccri' tube thc electronn r;~-itte!'ed \·!hen· the b~lDl .. ". strikes the ',tar50t.are collectcd in a. mode. rflthor. likti·:.l photo-muJ.ti.plier,

: :- aeaiii the sco.ttc:r ,varieo i,.rith ·tho imngepattorn on tho ,t<::rcet., Z:...ch muthod ''~: . l'.a.o. advarlt~ißeß t>,nd, dii..'ldV'DJ.1trig~$~ Buch as cli:ninritu1c lloisoin i:h:: blaclt al'eno ..

" ~.. " ,,'inthe'isocollf \-;hich i5 a problem in thc inol"e5enaitiv~~ orthic:on~ hcwev~:,.tllG. . • ' :. vidic:on mode ~o :l;econ1o' widcly uscd e>:.cept in seme, speciAl app~licat::'o~s~ . ., ~ : .;;, .":". "." , .,-, I' " •• ',~",~ •• _~, "," •• ,'''''•• ' • ~ , .. '.: " ' .•

VariatJ.ons, ell t}lt>.,.!l.:'onertl.cs cr· v.l.d:tE.~rgec~, .

\ '

. .' .. "The'iniage, cit an objectis ':f~cusöcd c-pt:I.C.:liiy thi-ouGlt the 610.03' end'Windo1ol '

., of tha TV camera tube~onto,the sensitive target lDy~r., Thcno~1n~l vidicon.tnr6et' is ~ntim6ny 'tiisUlphidc, another.$uc~eo€iul.vidicon'trirget'useo l~~doxide' (ret;istercd ut a 'Plumbicon 'l>y ·PhiJ.li·pt.;). Reccntly, cince 1970, .

'"., stlccessful v:td1.con tari)ol:u' havo been ctchcu fro:n Gcrni",:,conductc~ rr.aterinls to ,,', forni" the silict:m' dioda arro.y. t~ü'ects;: II;,16 there!ore ·,essel1~iaJ. tö. uriderstar..d

. '.' somo o! 1:.nQ spccific -pro,pcrt:1es of, these targets in orderto unuerstarid their .optimum oppliciltion~ .·.·These propci~ties can be dtl.'llt vi th undf:!' '~~lect!'al

sensitivity, rapidHy of" r~Sl?Cl1::.e or lüg, <.Ull"a.Z()-~hil.it~r.and ca."l'.r.!D.or· contrastrepröduction~:' .. , .

, .~. ..-- '.

Spec-l:rriiop.nsitivÜy dependsentirclJ' '()n the r!~011f7~tic5 'Jf the· br,=t~t ' ..uated..!ll.; ,Thc npi~L1<ll antimon:;' tl~iE:;ulphidc'vidicon tub~ ·is ric~r .'pv:nch."'Ol""..-:.tie ,and mntchris the h!.ltittiri cye, but the, 1.cau odde, i}J !"') t ncn~itive to wnveler.~ths

grenter tlrin 6oo~n..'l1· :.ind, is' usefttl,for, ßrcor., blue' an1 ultraviol~tri.nd is moresensitive to a.ll 3 th...n ·tno ant;it1~my tri~i\tlphirle. 1"he fJiliccm diode D.rr~y i8

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more ,sl;ll1sitive to all visible w.:\ve1.engl:lw und i5 not8.bl~ ,c>c:anith'p. in,red nnd'infra-·red l:eSionu Hp to. wayeler.gths of 1000 r...ll.. 'l'ht>..,e ttrlded rcgious in red 3ndinrra~red whicn.Q~e not seen by the other vidicon tubesroake thi~Particu~lJ

suitable f'or·beh..'\vicur observations where s:lall.amoüots of red light are '. .least.disturbing to the bbser-,Ted animalS. ;''l'he 'silicon array is also oeruJitiveto x-rays and electrcnn nnct ici,idenl'as ü caco~d ~t~ze in n p~otocathoda 'intensifieu ~mcra. Iiotc that tho opectral ~ensitivitY·iniritensifiedcamerasisnot' relnted ..,to; the target property hut to'the extra pho'tocathoce; aiid again ,a wid~ rnnge·of·phetoCäthode materials are'uscd W!th speci!ic spectral 'responses (Sobieoki and Wa~ulcri1972)~ .

, Slowncss oi Tl~spo1?se'l'or UiegH, in .t.hc arit:i~16r,y tr'iriulphide V;;"Q:\.cou is ver,.. noticcable it:hen ob:;erVing. movi:lsobjccts, ,l)?:rti-::t~l<:Lt'lyölS th~ light level

becomet,j ·clooe tö, the minit.\..m usef.u1.. to. thn cit.mcrb.~ In' no=m~.l ßccd lightingthis i,.a.lesn serioüG ui'J1.f:lOa an-ilyoin.·ot: ~:)~;tr.a~.cbjer.:te 18 i!;!portn.ut;·P1Umhicontiare.bot~erintpod li8ht:but~deteriorgteaoliglit is·reduced but,tbc silic"n diode vidiebno" are ccn:.-;iatently. the bcst;"The: ,l3.g propertie:i cf a.

.Cat:ler-a~..n be 'csaUy dcmC>tll3truted by m.-inginGa .bright· white per..dt1.luci across L\.

dark backgrmmd ~r a dro-k penduluu ovel" a p,ttterned bacl:p:.f'ound euch an &' ;. .

tt::stcard pluoe,a,'·in·frcnt. ef thtJ" cQ,Ui~ra,' .1)<-pico.1J.i, ir.. thl~ autin':):J:r tj-io.ulphi,da.or lass' so in 'th~ lead 'oxid~ v;\.tlicon, tlle' it1<:toe '01' t:h'l: 'elOl'lng 6bj~C~ h'a·'ofl c\wbite t!"!iJ.l acros'Sth& Gcrt!e-n~ tbC, d.a.r1~object nppeai~ quit1:' tr~n::,;.p""L:,ent'· .. 'o.gaiiu.t the li~t~ p.~r.t. or th" static b:lckßl'ound. In t'.'ClJ:1e· hj frame i~~J1tlisit,ean be Goen·th:-,t 'het\tet>.n':lO - 20 eean5.of,th~ bright}:stdll1rt: l~cql.\ir~'

, bo!ore tho :u::cGc i~' r€J:'loved trom the catnern tubo. Tbe [;co.~lj1l$ beam iri not nble'to 1111 the el~ctrQn eoleD eauocd,by.the brj~lt ~hite area, i~ th~ eloctricalcaimoity of thctnrget io too- high~ . 'l"nQ Dllicon died", target ß.:l13 '" i'ach slI'lülercupacity and li11)st., highliihts ur~ oleared ':from the t1'1rg~t: \ov-:,ttü:t 2 01' 3 scal'lG crthe :i.roage. This aur~r1or }lI'Opcrty cr tlto silicon. <liode 1\:.--r3.j i:3 invaluablein movement a~lysiö; 6mc~rinß bocomes ne~G.gtble ~nd ehosting ~d tral\~Cncyof, inovi~ß' obj~cts ifi I?ct seriouB even at high .5!)F.-eds.. . ,

. Tlie ant:i.!riony;tritiulphide vidiccm is .....ell kuo\m for :tts propt>rties uf :L~pr:lntine:a pcroancIit (burntou) i:r~ge if leit with t\ bx-if.;l1t chject focut:l~ed ('i"l thacamer~·tubc while thc G~\n.iG switched ~fr. In th~ 196~ rooen ~~!dingtte ~~~ern

was ,Ml'.1'!ßcd by F'Jinting tow-;al'US tho rilill.· T;r:.s unci:nonl t.r.i!>ulph.id~ vidicc&'l \'lhen'Used \llth atito~t1c e;aitl~ can also be,<.lazuvßi'!d if left G"Wit~hcd on ·"HE th'; leiu::cap on," or iri. 'tao: J i ttle light, this ia be<~s.1t~le thc' eCl!sUivity ic Aaue -toincrease auto:nn:tieSlly ai;·t.he lieht drops, by incrcaaing the volb.lE':e tH~rcnsthe t3.r~(!·t. Tlie i~ad exid~ vidicön 15 siw.il~~ 'in t1.11 rc~pocto,'to !;he al'!dl~Onj'trislllphide vidicon. The ciliccJll. diodl) vidic()tl hmmvet', ,i~l nc-t ·(,'k'1lU<.\ged. by iin­pririting; canno::' ba fitted with the ~).u~;\)C!a~ic UJ.in oyst€m antl 't:(lJ or,ltG5 Jirect ,bright light~ ThiG tube ~l..:.!.o:~ey'~l?p~d·:Iol'.U:;;~ in the pict.~e telt:',i,ho::lc unuwas used on the subscqucnt mcion 'trips becClus~ '-ai' 'Ha cxeept'i6r.aJ. elldurane:ä(vloolg3.I' and Benne.:.c 1970).

The imace contraat. is tccr.nic!iily speciiicd 1:; t~(!' sar:11T'3 of, t~(,> cO!:t,~r..l e.nd:La particularly j.~port:ant wh~n denlin(! \-1ith mcnoc:hro:nat,ic, lig.~t ~uch ~~i3 iR' ,found' in' deep \'!ater er in experimental. condHimlC_· 'rho antinl<:U:; tr.iculphidevidicon,,'ovcr 'its "10rldng rang:;! of light intensitj·, k.s ci. gCL"1l~ of 0.6,5 (ror100% change in light illtennity' the oignal cui.·;,·c:;t cl::lrlses trxough 6;i%).Howcvur, the TV %l1onitor shO\~'s' a. c(jmpl~llent~1.'1 f..;nJ:;r.J.:L 'C\t.id th'J.s gi\"e~ .",' tr~msrcrwhieh in 1:1 .. ' Ti1.~ siliconätode ha:::: a. nigh€.r l;'))~r;."3. cf 1 untl';ln'Ilrnct1co thiGmcana tho.t 'tbe :dlicon diode tube ainpli.fi.c~ the C~r.I;!,;1Sl of n c.:rallcr (6,5Jt:)portion of t'he lJh.:ldcii. betweeu wlJite anti bluck p:n-:neute-d by tr.c .:m,timonytri6U1phide Cl.l.!iH~ra. In thi3 wa::{ tl'iri COUt"t':'3 st ol an al1r;.-r:ey tKan c: ,Ü~ mueh

. enhanced bj thü ~i.licori diode vid:.con.. Various circuita ,c.:ln be' fitted to, ' sUicon diode c<"\r..erns t6 co:~trol thio cont.r~st (.'.~plification;..

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The nccuro.cy of ,thc>' pictl.~,a, ,~h~p'~, an~1:hö detail 'withi."l the.llicl;ul·e :iro ,,' ,m:lintained in televinioll as discuused. ünC:fer' the"tetevisiö~ \iUvefcrrns.: 'Triere.are 'in cach analysable field 237.5 lina3'oach ~ollowing the:other,by c~ct~i64/us:: , Tho spaciitg of these line::; and the rate nt' \ihich. the clcctrcm be~" ': ,Beane th~ width 6fth'c ·s6r~en,1s not howe'iter, c.xnctly,tir;wd. Mond iG·l).prn..oxima.tel~'

, . controlled by- lnacy different: techUict'~'t inagnctic' or elecb'o~tnt,io:.s;ystcmG~ ,:,:' ".soIlle are expensive: ~nd more l\ccurate 'tlw.n others which are cheap '::.nd cru~a.;,

',:.' Thc' setting'up of~'the gool:1etry inthc ca::iern arid '~helltorJ.tor c,:).n bc tediolls',: ',imd difricult. ·tt.~hou1d be-notcd th.:"i.t for. zi1r.ple surv-eil.h~nc~,:cr eyel;i ,

, ',,' domest.ic TiJ pur110SCl>; ri. hrrio' cicgrec', cf distcrtion cvu' betolernted anl ~V'cn

not noticoo;. but ·.fOl' '~ny scientific purposos the accUl'~\'C;)~:of the gcorJctry' i5.~ all, imPortlint nnd: c:m be tec}micall~t li.oiting. lt i5 pcnsible that 'whcl~e

• _'äccUiate'geom~try io important cow~ercially.availnblanurv.eillance.cameraodo';iöt h:we sufficü'ntquality' in the gncmetry control and 'a rntrpO!3C b-::.ilt;reseai~h camera iri-ncedcd,with this pnrt?f thc camera ~~rticularlywell 'aelected nnd detrelopetl .. ·. f... British·sto.ndard,e~istß'!or dOGcribi1ig andllltlsuring'

~ '. the' seoruetric distortion. in the TV monitor .(!\non t: 196}). A~ .eltictronic" gr~d.. ,'.' insertion devic~'is invF.ilunblc for settinGup ~nd chccldnc; .tho GGol'liet~i of a

TV :3yatem.' '. " ,

•., Resolutiori is b.inlY i1J:.ited by the qualit) of th~.:, c1(>ctronic c:~l."'cuit;s inthe diffcl."'mlt piece~ or'appa~atus ueed.to proceC.s '~he wavc!.orms. In '

'a system ucing video1:aIlQ it i8 Ilormally ,thc. video. tapo recorder \'ih.ic:, limÜ~ thc;resolutioii of· th'''3 r;ss-ta'ci~ Ar; mcntiotlC'd ,in the Gection :::'CO'l6 on t:l11evision

" ,~vcfoi~ri; :,a single anal:rs~ble'fieldhas 287.. 5 lincs, tho scannil:tß ripot MO11 finite 'size und codes illforci~tiön only .witilin ,its Oi-m. '·lidth~ Thus in al1Yvertical strip of a sinrrl~ f'ield 'hiere ctln or.ly bc 287.5 :pos~libl~ ch:mze5 ofd('nsity. In the, properly interlaced moriitored imszc thcre cot'lc1 appe;:a' to

, .,the:eye t.wice this n\lmber'. o~ vertical cr..3.n~eG~ th..-it io 575 1?ctmihle vertic.ul .'chanees i.!l dcnsity, rcprescntcd 6n the SC J:"E:en.; , The ~pat ero=rH~13 tho 'width·o.f'

'tho field fromone sld!l,to'.tho othe:r.··in 59.2/us and tnkee Ji.8Lus to return.for. the ·ncxt line start • .'. ':rho rate at, which 'the Gpot c~n chanee fl'om black. to' ,

, white 16 limitcd by ,thc contrallin5 electronics.. ' If tha electro:iic, circuits, '.:can' ccip~ with 10".0)0,000.. chane;es per scc ,(10 HHz)' or 10 tir::ee '!wr,1;uo,. the

spot· can ba made,to repreaent 592'changes'from black to ühlte durihg n singleline traverrie. '. I[ tlic frequerlcy responne ol thc television, systi':::2 ,1.s·:tochilic.:ally st1.ltE:d as 10 ,lü!z,:' 592 wow.d be the"l:la.rlmnm ntre1ber of Cha.ilgi::~ that

, the, system could resolve' in' the, picture width. TV reöcluticll i:s ~lor~ll:.,:'e' 'expreGsed iri'linos ~pcr picturc height and thiß fötslld3rd ,refcis 'to nconditi.on where a ,lin~' and. 'sprice are ,equnl, in si~a anJ. this l:-\"t eX:ir.:ple

.uould .be statcd',as a, 'h'o,rizontal" resolution o:t:"l~4lt lines. (io the hcigh~ to", " width ~f-tio x ~92r;.·:!" ~e'sol:lt'ioh :in; most f)1.ir\r~llj.~c'q J;al!i~ro;;' i,fi goöd und' the

_ rrequE.nicY responsed ':noroUY \iell c.vcr 10 }!1!z. . Vi~e~ t~tio rf.'ctlr=:'c:rs us~~ly, .', '.' demonsti-ate 'no more 'tfu:n' ,5HHz 'responac "ihon rcplajirig' the reccretid. wa.veform

",' : . Md verjr. orten ire'~peeified'aalow aE 3!'U!z.. Iil pract:ice, tlm resolü~ioii. cf.. a sing:J.e fielc1rcplayed oy a -;; l-iHzvidco tDpe recorder is licited }::1 the .. : recorder to'28?5 horizontnl line3 'and 296 "lertical lÜ16S reI\rcsontirlf; n

" limit cf, 28'1.5 X 296= '170, '200 poc:1ible picti.u-e 'clements. Note hci...evar,'. that. ·rcsolu·tion, of truly _hor.5 :oncal,lines 'is o.!fect:cd hy. the cx:tz:..tl!nce cf'

: '. ,'the horIzontal' TV linen nnd variouci intcrIcrence nrtilact.~, Oilf;~ \-lith the, other, can occur.' " Intorference artifncts of D. diffe:t'onl: type C!l.n ','ccur with.the diode' el~mcnts etched lnto,the im~go'platc of tao ,silicon diodo urray ­vidlcon~, Thl1re ura in, thc Dilicon diode' vidicon diocrote nut::berr; cr. silicon'diodes ctched into the face plate e:'lch ttcting tts,a. llicture '~lt:rntmtt l1arr.agoddiodes are'visiblo 4\3 blä:ck or ,white upotö peruo..''lt'.mtly in the picturo'- As ci.rou~l griide'there.~~ be adiodc.pitch:of,64 p~r mm'of tube.tnce spRceu 14/ume.p:lrt •. Araster :Ln a 1 tf (25 It::t). (:o.l:'~rn t.llUo of 12.? l'r.'ti x 9.~; n:m ~cntain:; 0'12 :(

'608 ':: IIT;, G)6 uiod~~~ (\-!oolf~;j..:" ";:l~' B~~rlt'et. 19(0).

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. Recent develonme~~z'in iow1i.ßht ~clovis~~n .eamer~

T.:ie gene:hü' opin'icn of 'u~crß appe:lfs t~ be t~t io, U:ldo::'i{atcr ,t.J."'7. there ,ha"lonev~r,~~en au~h.good rcsults as ~uve recently b~en obt~uledu~inga ccimeru,fitted with' the 1\0'\ Sit cancra tube (ROA. 480ft.},;, Tb.o RCA Sit tube !:.S.D now

.' -been' iitted"by' several cO:3norciul firms into unöcrwntex- TV.c-~~eras (,e~ H;"dro-products,' UDI, Eil),;, ; '?na Sit "tube is a oi~icon diode v.idicOI1 \lith an ' .

.. ~ interi5irier'ßtaße~ Tho i~~gg is for.med Viaa fibre-optic'face:plate,cu a.Na-K-Cs-Sb . (e.t.lti-a~~a.ki) ph6tocathoc!o .which ba$ a pe<J.l.(,1ight s~nsith..:tt~ in. tbe greena't 420 + 50' nc. Thc"nicturo information ie tr;mzf~rr,~;i Dnd ", amplified onto' th'; silicon diod.e' o.rra:; tllrget an:! thcn Bcanri~d in -ehe, nOr:T..:ll

vidic'o'n mode. "The tube ch:ii-v.cteristics relevtuit· to th'; Ul'wr a::c; pr!:sr.::.-.ration'01' the,lo,'l lag rcS"~tinb'in vcry little ?IlO:~t'ing of l:lovinc h5.ghJ.ights.'even utthe lowest light levels; a' gtl.'!i:r.a or, unity \lhiehrc~:u1to in'CUh'J.llced eon'traatci! images llhich art'_ tYr>lcally- öf lew contrast u.nderw~,ter; tb.? p~cl1: ::>cnsitivity

"at the rii6str~le'l.?.!lt '\oIavel~nsthfer naturn.l~ illu.-niItation in th~, !;~a., 'Whnn'tMs 'tube is l::uilt ioto !t. Otll,histfca ted 'C:lI1'!t:ra 'having automatie ccmÜ'ol of dieltnts, iris' E\nu suittl'ble ,filters, . thon thc Etd·rancage of the tube' s d)Il1.\ciic.. 'iMge from hright: d:l;,ylieht to nco.r moonlight sC::loiti'\"itj bcco::neo ideat~ tor .,operation by, a. diver. Intensifier 5ectionG h:l.v~ teen fit-tcd to.' other t~~e:::-cf came~ tube but·tr.ernajor problem h~5 alwnys b~en thc serious in6r~~so i~

lrig or sme:.iriii&'~hen the licrht level of: thc objcc:t' is recluccd. APllliro.tion ofthe silicon 'fHode arrz..y in ths'Sit tube hila Rülved this problt'r..'t und 11.6.~ lodt6 a ncw', family cf iow licht cmnerua usaful in h:ccrdirig' pictu!'e3 cf mo\-ins'objects~, Thair Ij r.:-:tl: lC\'t}l pUl' Icrmance i6 'UprrOzl.ll'latcly p1\l'~llP.l to the h:..t':'.:lneye, thol~. contl,'n.st 8.i:'plii'ica.tion :in 6.1.nY eil' cü~ot3li.Ce5 g;t\.-on slight ir.:rrrovemcilt',O::l the divers view.. "

Other ~;"ir~ ~r ~!,p,t.el~i.n~.:e.icturen. io~; inov~!US'nt..mla1J_~~.ilThe e:mct 'timing 'lnhcrent 'in· the TI 5~mtci:1 ic lnv:lluable in scientiiic

:D.:Daly:iisof 'n:ovemeot•. ' 'l11e, major disadvan~~,sc ia tho lacl: o:f a "huttcr er, thc. ~l.cam~ra:,so th3t n b:l.~r:d i.map,& iti.!o·cr::ed,o! ;:\ ,~cn~tantiy'lit rr.o\'i.!lf~ objcc;t. A

simple way to o.voJ.d th~s 3..3 ·toarraDGt"~ a rotatin~ diec in front \lf the c<lClara.

with slitoallo\.,ing lisht ,tc entf;'r thc lenr. fot' n 8hoi-t pe~~od cr say 2 ms (Wi!scm- 1970). ,.'Thn target, eJC.potie.ü in this ""ay.~cmodse.s,the1t.tr·ozen" i!nt'lge until i.t is ,. sca:;medoff Uj th", eleclron booU:. It ia pracHcal to rotate thc dine us;,ng"'amotor' E:~lich:'oniB~d t6 thc tuiua .AC fTP,9,.ueney GO, tha.t .the tar~~et,ic f.;x~~eÜ .

.' once, twice or" .cavcral tit1'ea tor each fi-:-ld scail. Electronic' flash tt\bt:~ ,z\!'caVa~lablQ ,;hieh givo b:dcf:fiashos('lOLU~),:,t ,:·ütci:J. U~~~('(,ti'l.."tn 100, peX' secnnd' control Gyste~s cnn lJe u~ed to s~m~hronl.n~, the flash wJ.th t1H: 'lr'v' r:;Cl\nrate (Wilstm ..1970). ' Tlt(;' pro't'lema of, usihg' url;lfi.cial lisht,~ u::ider'",ater':tre'discu5sed by Rem:ninga('!9'72) ... Slrnl)~ tubeaaf a low 'P?w(j~ 'outP\lt. ~11, gi~,c "excellent r~::lülts 'f!llEfH illnmin.3,tinif a. ln.re~ ot:udy arp.3. it" tlnc~d' i."'l' con~'ul1ctiönwith scre€'~r. coa tc1 with rerl~: 'X'cflector n::a:t'..lriul (CE; tr..'l tC'l~ial uSi;d. in . ,rerle'ctir.g rocid .s{~n5);';· .. Roflex r't-floeto:" 1:::lbirfuls l'et1.lrn light· to, thö :;ot~e~,so that by p1l1cinS' the ,sti'öbti light next t()-th~ c:1.t'!~m lcri.s n .prn:::ti'c!:J.l returnto the lens 01' over:9\1;t.. 01' the strobe licht atrLl.(j.1lg Um. screen,is c\chicved.:; ;a principl,c used iIi':'th-i ciucll".t.. inJust;ry (Vl:thOi~1972).. ror öli-,,·..ll)'Gie or fastmoving !ish, i'r",mc: rates' ui: to 200 p~r 6ccbnd..aro l'ct}uired. , 'Ihe pictul'c 1"atc

,in ,TJ.orlO'll T'W ~~rci~elnri if"';"'> :"::,~lds per HflCQIH.1., !Arid v:s.r.l.C"ls ~et'J:lOds e..l'C po~sible

for incrcc.r.ins thi.;; rnte \ldug a ottUHJard t:losetl circuit 'lV cyntf':m. 1'h..isuGually meano cutting down; tho JlUL1berö cf 1.ineo available ror pictUr'o .iniorm3.tiou by· reGcanning thc 'ilhole of. tho c,'lrner"l target r'1Ör~) f ...~eq'J.~tlY \·tithfeHer 'linus (\~ilson 1970). or rcoc".\::ninL~ n" 'Gm~~ll, Dcc:t,iorl cf tho ~nr:gC1.t mora .

'f'rcqüently prosari'in~ tha linc d~ncity. : This·lu.~t ul",thod h<.!:3 prc..,cd p!'<lctical.ror analy~;in~ fisti cwir.:ming rnovc:nenl;r,; at thf: Abcrl1f:~n Harinc I".qbCoruto}'y~

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At' Aberdeen an acia-ptation cr the' rcutinö"di~er observ-J.ticn;J cf '::ishiz:; geilrsh'lB allowed· th~ diver held 'television eamern' t,:, be nuccer>sfül1y u$ed c.ll tl~e

seine net and trawl ~~r. , ,The uormal divcr obnerv~t~cnc ar-e ro~de .by t.hrt';edivel:'c~ two free' Sliir.:mins 'and on~al\1l?yo:in contact 1;;:r a telephone fror.! theheadline to a rubbcr:divers' bcqt abcve the nct at the ourfncc, with ~. VI~;

l";;:.dio 1i1'J: to the towing shi.p (Hain e.tld G.::.pgster. ~976).. In order to ~fel.;­

operate. tha telQvlsion ciiloera on the geal"', Cl 6. m. covered motol'"' bcnt '.roplncc6the divers' rubber ,l::c'a't,. tha .tclevinion, eable with integrnl ,t~lcphona..:'conductora r·epla.ce:s the nOl·::::.::.l telerlhc~c' c~ble ül1:l 11 frce length cf {'-üble l:.llo~s

. '. thc divers. tö range up tri 20 m either sido of thc hc;).olint't lltt:l.cl~ent poir.t.'A pärtr'Able .;}Il video t~r.c reco:'der; a monitor, a cloclc 'IV ir.zcrticn t!.."'1it, and a 'transvcrter p·:>~:e:r ur.it thi.t ,(l110~'IS thc. ope:ratiOI~ of thc TV usirie two car ' .

. biltteriep supplying ;24.v.olts nc, are nIl houned ill'tli." c.:lbin cf th'3 :lioto:- boat., Using a COlllpe'lct underwater. ·c."l.!!:ora ritt~'d with an Re;. Si,ttub~ <~nd complt!te. autorr..'1ti~n o! tha expcsure control, useful rc:a tir.lo video t:1P~ ~·I:c.ordci h~"ü

been mad~ illustrating r.:o.ny it'lJ'lOrt.'J.llt f€~.d;ures ol fishing p';<.:"CU'!;l '~;'::;:l::2lin~d. A ,further ~succenßful dcvelop:nent of this t.;chni.quü i~ tc ril:: the 'i'V ccrr..ciU.r.icatiohca'bl~! from the stern of the towing ship. ThiEl zrrrangerr:;;-nt will D.llo,." rccord3e ,to bc made of dC::'iel's:Jl: ond pelagic trat·!ls 'tawil'1!~ at lüglier speedo•. 'l'h~ problems

. .cf thc divers in t;.il~SO aituntiom.i.:\nd hQ~ thcy ~n he sol\'cd are cllsct4~sp.d b:,' 'Mnin '.::.nd !Sa!Jgsl eI' (1976).;' .

"

~otogt?:ph:v: of TV ;fram~g :J .

In o!"deri to ano.l~toa rnovome.nt or niake":pel'ean~l1t ,Ül'.15tl'"a.tioI.\~ of. r.N ima~s it

is possible to copy dircct i'rom a. TV r.:orii tor onto rUm. To pre.r.l'11"\Te geo'Xetr:; .the picture Oll tbc mOld tor t:hould bo ~lt lC~t~d; 307: '..mdcr:;cl..'mlleil ~:o tho.": the image only

'. occupies' the relativeI:; !laI: centre part 01' thc f.'lonitor tllbe. DUf~ t.o the,constant: spot ei~'.:! und thus con$tnnt: li::te thickr.:.ls~, ,thc bcz,t· :::izl'J öf TV

. pic~ure ~o:- I>l1otoGrnp"ny. 18 Cl 23 - 33 cm (c1inCol1aJJ pict\.u'e O~ .1. 5{)-70 elf.. serGen. ;The sinsl<.:.fiold Bcan' takes 1/50 sccond ~nd i.t i8 diffict.:lt:, tosynchron!oethc film c~mera shutter ~ith tbc senn. Th~ bost rcsulta ar~

.. cbtained :.by photo(';raphin~ a ~.dnB1(,\· frrur:.t! nr:lrl <)!I~t r~:plr.-,yc<l fl'ort; a video. recorder and. making an expooure ~f lIlf necond~ . The une of uhorter exponut'e ti:.ces .'results in ~ stripe nC!ross the copied.ncgativ.e w~~re P::t~·t of the }Jic(;ure isscalmed.Qnce~d~nother t~t twice bythc electron b~~m. A 1/4 second

, . axpOtsurE: .a.llows time ror about 12 scani3 \ihilr.: the shutter is open and the ..'e .rolati.ve e!fect on' tha exposure of a.l'l ovcrl!\p of tlw first nnd lnst 8c..'i.nS

i~ neelig'3.ble~,

'. Cinefilm of a short.sequ~nce can be ~~de from single TVfic1ds in th~ s~ma

I·,. : manncr with a suitablo CCl1l'lara. I. real time. Ttl 5t'qucnce can be copi~d usinsa reflcx,cino camera at 25 frnmca per second by adjunting tho running bpeed

; so tr.at n h\)rizontal bar i~ secn at.the· top Cl" 1:')""0(' r~dG': of the' f1'"~ne se.;-n. ·in thc' vicwfinder. S!t5.l1 is needcc1 to keep thi:; bnr lwrf,~cny I":til1.; In this

., '. ca::.e it· wHJ. bE:: found thnt c\'cry oth.er 'rV field :i H Iili::;t,;i~g nnd thic r-r?cessi':> not suit"~:'l(l if ul1 tieid:; ure required for anüly:'iis. .

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Refc:t.'enC~6---.... ...-linon (1963). ErU:ish Stot.;,J.r.rd No.. 13s}':'~;'9: Met:h~~~ fOl" !Jloo.s'.l:;,~ing 1.I.';1d

e)wressing ~hepcrfo~~?oecf TV re~civers~

."Anon (1968) ..

Hemmings, C.. C.. · ("1)72).. UnderwateF r:hotography in fic'.lUel'ÜlL'i rcscarch~.. C 'f"'" k U 34 (':öt) f t;r 1 "1tI. ,ans. ~n·;" ,:..,q)'.or. ner., ;" , h.)t)-·-K~=ta

.:~. •• ~ >- •• -

&lbieski .. ··s..·k..nd W~:P1C;',' E~ J. ('1972)~;' Aljv:m,~'ed.t;lectro-olltical ·imag-:...ngtechniq\J'es; 126 pp. Proceedingfi cf. a" S:rm'pcs~üm hdd at NI..:JA' n$a.dqu,,,,rterspl~blish6d ~by Ua:l:h;öJjl Aerouau~ic5 and Sp~~~. Adrilinistr.<ltic'n, \:azh.in.~on DC.

Wilf:lon, A. (1970). A hi;hspe-e~ täevhdon rt'~ording s:tstem w-:.th ~lov' 2.l1.1.

. , ""stop motion :rcplay,,' . Royal Airc:rt:.f.~ Establishment teehnic~t.l rr:p<lrt 70035,' .. Febt'iJary 1970, '13. pp~ Ave.ilable 'from Hinistrj· of Tech:nolo~;j':Farnhorough,

'Ban!::;. , '. .' , .,

Woolgar, "f.•• J .. and Bennet,' C. J. (1970). Silicon rlioik-:;1,r.:-t.\V tubr':s al1d tar~ets.

. ~P]al. T.:.2..~~i2..1L!,'?c~etiJourr~!, 1i· (?), 53:-;>8.:,

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