Cảm Biến Quang

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CM BIN O QUANG Nhm thc hin : Hong Cng Anh Thanh Tun Nguyn Tin Thin L Xun Bch Ni dung 1. Tnh cht nh sng 2. Cm bin quang dn 3. Cm bin quang in pht x 4. Cc loi cm bin thng dng 1. Tnh cht nh sng 1.1. Tnh cht nh sng ncv =Ph nh sng c biu din 1.1. Tnh cht nh sng b)Tnhchtht:nhsngbaogmcchtphotonmang nng lng, nng lng ny ch ph thuc tn s (v) ca nh sng: Vi h = 6,625.10^-34 gi l hng s Planch MtintclinktcnnglngW1,gii phngintrakhinguyntcncungcpchon nng lng bng nng lng lin kt W1. -Hintnghtdncgiiphngditcdngca nh sng lm thay i tnh cht dn in ca vt liu gi lhiungquangin=>ylnguynlcbnca cm bin quang v =|. h W2. Cm bin quang dn 2.1. Hiu ng quang dn: Hiu ng quang dn (hiu ng quang introng)lhintnggiiphngnhnghttiin(ht dn)trongvtliuditcdngcanhsnglmtng dn in ca vt liu. + in t hv + hv - in t hv + Vng dn Vng ho tr Wlk - - Bn dn tinh khit Bn dn loi n Bn dn loi p l trng l trng W>Wlk 2.1. Hiu ng quang dn - dn trong ti: - dn khi chiu sng: 0 0n q = o2121.1u =|.|

\|= =A rgq n q o0o >> o v l hm phi tuyn ca u vi s m =1/2 (thc t = 0,5 -1)2.2. T bo quang dn (TBQD) a) Cu to: thc cht TBQD l mt in tr c ch to t cc cht bn dn: a tinh th ng nht, n tinh th, bn dn ring, bn dn pha tp. 0,20,612345102030 CdS CdSe CdTe PbS PbSe PbTe Ge Si GeCu SnIn AsIn CdHgTe , m Vng ph lm vic ca mt s vt liu quang dn 2.2. T bo quang dn (TBQD) b) c trng ch yu: - in tr: in tr trong ti ln (t 104 O - 109 O 25oC i vi PbS, CdS, CdSe ) v gim nhanh khi ri sng tng. in tr (O) ri sng (lx) 0,1110100 102 104 106 106 1000 S ph thuc ca in tr vo ri sng 2.2. T bo quang dn (TBQD) - nhy: Nhn xt: + nhy gim khi u tng (tr = 1) + nhy gim khi tng nhit , khi V in p t vo ln. + nhy ph thuc vo bc sng nh sng. 1 u =AuA=AV IS2.2. T bo quang dnc) c im + T l chuyni tnh cao. + nhy cao. + Hi p ph thuc khng tuyn tnh u.+ Thi gian hi p ln. + Cc c trng khng n nh do gi ho. + nhy ph thuc nhit , mt s loi i hi lm ngui. 2.2. T bo quang dn-150-100-50050 Nhit (oC) 10 5 1 0,5 0,1 nhy tng i Bc sng (m) nhy tng i(%) 12 3 1 3 5 10 30 50 100 nh hng ca nhit n nhy ca t bo quang dn nh hng bc sng n nhyca t bo quang dn 2.2. T bo quang dnc) ng dng: -iukhinrle:khicbcxnhsngchiulntbo quangdn,intrgim,chodnginchyqualn s dng trc tip hoc qua khuch i ng m rle. - Thu tn hiu quang: dng t bo quang dn thu v bin tn hiu quang thnh xung in. 2.2. T bo quang dnd) Nhc im : - Thi gian hi p ln . - Cc c trng khng n nh ( gi ha ). - nhy ph thuc vo nhit . - Mt s loi i hi phi lm ngui . Do ngi ta khng dng quang tr xc nh chnh xc gi tr thng lng m c s dng phn bit mc nh sng : trng thi sng - ti hoc xung nh sng. 2.2. T bo quang dn+ + iu khin trc tipiu khin thng quatranzito khuch i T bo quang dn dng lm pin mt tri T bo quang dn (quang tr) 2.3. it cm quang (Photodiode) a) Cu to v nguyn l hot ng S chuyn tip P NVngchuyn tip E P N Vng ngho Vb Vng ngho 2.3. it cm quang- Nguyn l hot ng: Khi u = 0 v V = 0, dng in chy qua chuyn tip: Ikt Dng khuch tn cc ht c bn. I0 Dng htdn khng c bn sinh ra do kch thch nhit. Khi V > 0 dng ngc: Khi V ln 0 v Ir = I0. 0 exp0 0= +((

= IkTqVI Idr((

kTqVexp Id00 exp0 0 0= ((

= = IkTqVI I I Idkt2.3. it cm quang- Khi chiu sng bng lung nh sng u0 Ip. Khi V ln: N P hv + Ir Vng ngho + x Hiu ng quang in khi chiu sng V p 0d0 rI IkTqVexp I I + +((

=p p 0 rI I I I ~ + =( )( ) X exphcR 1 qI0 po u q= nhy ca it cm quang- i vi 1 bc x c ph xc nh , dng quang in I tuyn tnh vi thng lng trong 1 khong tng i rng .- nhy c xc nh :ng vi S

q hiu sut lng t R h s phn x o h s hp thh hng s Planck h = 6,6256.10-34Js c vn tc truyn trong chn khng ( )( ) ( )o q|hcX R qIS =AA=exp 1 nhy cait cm quangty thuc vo cht bn dn l Si, Ge hay Selenium Hnh v sau y cho thy nhy theo tn s ca nh sng chiu vo cc cht bn dn ny 2.3. it cm quangCh quang dn: Phng trnh mch in: Tn hiu ra: =>ng thng ti A. =>Dng ngc:Cm bin lm vic ch tuyn tnh VR ~ u. Ir VD VR Rm ES + A 0-10-20-30-40 50W 100W 150W 200W 20 40 60 Ir D RV V E =r m RI R V =ES mDmrRVREI + =2.3. it cm quangCh quang th: in p ngoi V = 0. o in th h mch Khi Ip> I0: ln nhng t l vi logu. o dng ngn mch:

((

+ =0POCII1 logqkTV0pocII.qkTV ~0POCIIlogqkTV =p scI I ~ISC Rb 2.3. it cm quangc) nhy: - S khng ph thuc thng lng nh sng u. - S ph thuc vo , vi s s: SSmax khi = p - Khi To tng p dch sang phi. - S ph thuc q, R, . ( ) ( )o q=AuA= hcX exp R 1 q I) ( SP p (S(p ) = 0,1-1,0 A/W) 0,30,40,50,60,70,80,91,0 (m) 0 0,1 0,2 0,3 0,4 S (A/W) T1 T2 2.3. it cm quangd) ng dng: ES Rm Ir R1 R2 V0 CP1 Rm ES R1+R2 R1 V0 R2 S c sS tc ng nhanh + C2 + + - S mch lm vic ch quang dn: r mIRRR V * 1120 ((

+ =( )rI R R V *2 1 0+ =2.3. it cm quang- S lm vic ch quang th: sc m 0I . R V =oc120VRR1 V((

+ =R2R1VoS logaritVocR2R1VoS tuyn tnh Isc2.3. it cm quangCh quang dn: + tuyn tnh cao. + Thi gian hi p ngn. + Di thng ln. Ch quang th: + C th lm vic ch tuyn tnh hoc logarit. + t nhiu. + Thi gian hi p ln. + Di thng nh. + Nhy cm vi nhit ch logarit. 2.3. it cm quangc) ng dng: - Chuyn mch: iu khin r le, cng logic, . - o nh sng khng i (Ch tuyn tnh) 2.4.Transistor Quang ( photo transistor ) a. Cu to v nguyn l hot ng: Gm 3lp bn dn ghp ni tip to thnh 2 tip gip E - B v B C tng t nh mt tranzito. -Phncc:chcinptlnC, khngcinptlnB,BC phn cc ngc. - S mch in nh hnh v. E - B C+ NPN Cu to E C B + S mch in2.4.Transistor Quang ( photo transistor ) Nguyn l lm vic:- Khi t in p E ln C, in p VBE ~ 0,6 0,7 V, VBC ~ E.KhichiusngtipgipBC ccintvltrngphtsinhtrong vngbazditcdngcanhsng sbphnchiaditcdngcain trngtrnchuyntipBCin t b ko v C, l trng li trong B to ra dng in t t EBC to ra dng ngc: Ir = I0 + Ip E C B u +E S mch in in th C B E + - S tch cp in - l trng 2.4.Transistor Quang ( photo transistor ) E C B u Ir IC S tng ng +E Dng I0: dng ngc trong ti. Dng Ip : dng ngc do chiu sng. phototranzitotngngt hpcamtphotodiotvmt tranzito. ( )0 Phc) X exp( R 1 qI u o q=Ir~ IB Dng colector IC: ( ) ( ) ( )p 0 r cI 1 I 1 I 1 I + | + + | = + | =2.4.Transistor Quang ( photo transistor ) c) nhy:

Ic e Ip e u v | e Ic | eu Seunhyphthuc thng lng nh sng. - nhy ph thuc (hnh v) S(p) = 1 100A/W 0cI) ( SAuA= ( ) ( ) ( )p 0 r cI 1 I 1 I 1 I + | + + | = + | =S() S(p) (%) 100 80 60 40 20 0,40,60,81,0 (m) ng cong ph hi p p 2.4.Transistor Quang ( photo transistor ) d) ng dng phototranzito: -Chuynmch:thngtindngnhphn(chaykhngc bc x, bc x nh hn hoc ln hn ngng) iu khin rle, cng logic hoc thyristo. Cho khuch i ln c th dng K trc tip. + + iu khin rle + iu khin cng logic + + iu khin thyristo 2.4.Transistor Quang ( photo transistor ) - S dng ch tuyn tnh: +Trng hp th nht: o nh sng khng i (ging luxmet). +Trnghpthhai:thunhntn hiuthayi(iukinbin dao ng nh): tuyn tnh km hn photodiot.

( ) ( ) t t1 0u + u = u+ Luxmet ( ) ( ) t . S I t I1 0 c cu + u =u0 2.5.Transistor Quang ( photo transistor ) hiu ng trng a.Cutovnguynllmvic: Gm2lpPvNghpvinhau, li l N, v l P, to thnh mt tip gip P-N. Tip gip P-N c phn ccngc,bnngoivngngho lcng,bntrongvngnghol knh.Dngquaknhphthuc titdinknheinpgia cng v knh: S G D G P P N + + + + + + + ++ + + + + + + +- - - - - - - - - - - - - - 2PGSDS DVV1 I I||.|

\|+ =2.5. Transistor Quang ( photo transistor ) hiu ng trng -Khi chiu sng, chuyn tip P - N hot ng nh mt photodiot cho dng ngc: I0 - dng in trong ti. IP = Sgu - dng quang in. Sg - nhy ca iot cng-knh. u - thng lng nh sng. - G D S + S mch Rg P 0 rI I I + =g r g GSE I R V = ( )g P 0 g GSE I I R V + =2.5.Transistor Quang ( photo transistor ) hiu ng trng c) c im v ng dng: - Lm vic n nh - H s khuch i cao iu khin in p bng nh sng. 3. Cm bin quang in pht x 3.1. Hiu ng quang in pht x - Hiu ng quang in pht x (hiu ng quang in ngoi) lhintngccintcgiiphngkhibmtvt liu v c th thu li nh tc dng ca in trng khi chiu vochngmtbcxnhsngcbcsngthchhp (nh hn mt ngng nht nh). 3. Cm bin quang in pht x + C ch pht x in t khi chiu sng: - Hp th photon v gii phng in t. -in t c gii phng di chuyn b mt. -in t thot khi b mt vt liu. +Donhiunguynnhnsintphtxtrungbnh khi mt photon b hp th (hiu sut lng t) thng nh hn 10% v t khi vt qu 30%. 3.2. T bo quang in chn khng a. Cu to: -Catot:cphlpvtliunhyvinhsng(Cs3Sb,K2CsSb,Cs2Te,Rb2Te,CsTe)ttrongvhnhtrtrong sut(b)hocvkimloicmtutrongsut(b)hoc hpbntrongchtchnkhng(psut~10-6-10-8 mmHg). - Anot: bng kim loi. u A K A K u A K a) b) c) 3.2. T bo quang in chn khng K A Ia E Rm Ia (A) Vak (V) 4,75 mW 2,37 mW 0,95 mW 4 3 2 1 0 20406080100120 u S tng ngc tnh V - A Khichiusngcatot(K)ccintphtxv di tc dng ca in trng ,ng do Vak to ra tp trung v anot (A) to thnh dng anot (Ia). 3.2. T bo quang in chn khng - c tnh V- A c hai vng: + Vng in tch khng gian. + Vng bo ha. -TBQlmvicvngbohatngng ngundng,cngdngchyuphthucthng lng nh sng. in tr trong ca t bo quang in rt ln: u||.|

\|=akadVdI 1=10 100 mA/W | AA=aIS nhy: 3.2. T bo quang in chn khng c) c im v ng dng:- nhy ln t ph thuc Vak. - Tnh n nh cao Dng trong Chuyn mch hoc o tn hiu quang. 3.3. T bo quang in dng kh a)Cutovnguynllmvic:cutotngtTBQ chnkhng,chkhcbntrongcinybngkh (acgon) di p sut c 10-1 - 10-2 mmHg. Ia (A) Vak (V) 2 1 0 20406080100120 10-2 lm 1,5.10-2 lm Khi Vak < 20V, c tuyn I - V c dng ging TBQ. Khiinpcao,int chuyn ng vi tc ln ionhoccnguyntkh Ia tng 5 10 ln. 3.3. T bo quang in dng kh c) c im v ng dng: - Dng Ia ln. - S ph thuc mnh vo Vak. => Chuyn mch v o tn hiu quang. 6 2 0 2040 60 80 4 8 Stg.i Vak (V) 4. Mt s cm bin quang thng dng 4.1 Quang tr (photoresistor) Thng thng,in tr ca quang tr khong 1000000. Khi chiu nh sng vo,in tr ny gim xung rt thp. Ngi ta ng dng c tnh ny lm ra cc mch pht hin sng ti 4.2 Cm bin hng ngoi a. Cm bin hng ngoi thng : l loi cm bin m b pht v b thu khng c kt cu trong cng mt khi. B pht v thu l 2 b phn ring r. - B pht : c dng nh diode pht quang, nh sng pht ra l tia hng ngoi - B thu : l 1 transistor quang,khi n nhn nh sng hng ngoi,n s dn bo ha b. Cm bin hng ngoi kiu phn x : L mt linh kin hnh thang C tch hp mt transistor quang (rt nhy vi nh sng hng ngoi) v mt b pht nh sng hng