Giáo trình kĩ thuật truyền hình

7/30/2019 Gio trnh k thut truyn hnh

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GIO TRNHKTHUT TRUYN HNH

GV son: Trn Duy Chung Trang 1

A. NGUYN L PHT-THU HNHChng 1 : NGUYN L PHT HNH:

I. PHNG PHP QUT HNHV tuy n truy n hnh l ph ng th c truy n hnh chuy n ng c a m t c nh

(ng i, phong c nh) no chuy n i xa nh sng i n t .Mu n truy n i m t hnh nh ta c n chia hnh nh thnh nhi u ph n t nh v

bi n i cc ph n t ny thnh nh ng tn hi u i n t l v i c ng sng c achng. M i ph n t c a hnh nh lin h v i m t ph n t sng v tr t ng ng v imn nh my thu hnh. V tr chnh xc c a t ng ph n t c a hnh nh r t quan tr n.N u khi t o l i hnh nh, th t cc ph n t c a hnh nh b xo tr n s gy nh ng smo hnh khng th ch p nh n.

Vng m c c a m t ng i c qun tnh: khi nh n c c m gic c a nh sng thc m gic s cn t n t i trong m t th i gian, ngh a l sau khi m t ngu n nh sng, vng cn c n m t th i gian m i tr l i tr ng thi ban u. K thu t truy n hnh l i

d ng qun tnh ny c a m t ti t o l i hnh nh lin t c.Ng i ta khng pht ng th i t t c cc ph n t c a hnh nh n ph n pht sng

t ng ng c a mn nh my thu hnh m l n l c t ng ph n t tr c sau.S ph n t t nh t c n cho m t hnh trn mn my thu hnh c xc nh nh sau:

Hnh 1 Hnh 2Quan h gi a kho ng cch nhn t t nh t v s dng c n phn tch

Th c nghi m xc nh r ng: kho ng cch d d nhn nh t t mn nh n m tng i xem l 4 n 6 l n chi u cao h c a hnh. kho ng d nhn nh t, n u ta mu ncc dng nhn khng b cch bi t nhau th gc c a hai dng k nhau ph i khngl n qu m t pht (1/60 ) hay 1/3438 radian.G i h: chi u cao hnh, n: s dng, d: kho ng cch d nhn nh t = (46)h ta c

tg( /2) = (h/2)/d = 1/(812)Suy ra: = 10 n 14

d

h 3

4
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Nh v y s dng t nh t s l:n = / = ( 010 014 )/( 01 /60) = (600 800) dngN u coi 1 ph n t nh l m t vung, th v i mn hnh tiu chu n 4/3

( ng 3, ngang 4), s ph n t t i thi u cho m t hnh s l:4/3x (625) 2 = 520833 phn t

Nh qun tnh c a m t, mu n ti t o m t tc ng lin t c, c n pht kho n25 hnh /giy, ngh a l trong m t giy, 520833 ph n t c a hnh ph i lin h 25l n v i cc ph n t pht sng t ng ng c a mn nh my thu hnh. V y trong m tgiy c n 520833 x 25 = 13020825 lin h .

Trong tr ng h p tn hi u th t n l m t hnh sin vung m t ph n t en vm t ph n t tr ng k ti p nhau c a hnh s t o thnh m t chu k .

V y v i cch qut xen k 25 hnh / giy, t n s th t n s l:25/2 x 520833 = 6,510 MHz

Trong h th ng ny, l th t n c c i, tuy nhin trong th c t chc n m t t n s gi i h n th p h n c ng m b o nt u.

T c l c th nhn k t qu trn v i h s Kell 0,75 ta c:0,75 x 6,51 = 4.8825MHz

thayth b c mbi ng m108 sensorc am tc mnh nhnh nhc av tth thng itas d ngcamera_thi tb g mm th th ngth uknhvccm chi nt chuy n icc i mc ahnh nhtheot ngdng thnhcctnhi ui n. my thu, tit ol ihnh nhnyng i tadngph ngphpqut,t ng

qutnh sau:

Hnh 3. Nguynlquthnh

M thnh nh t ngquts c c t ra thnhndng,cc i m nh trn

t ngdngl nl t cchuy nthnhcctnhi u i nc m nhy ut ngngv i sngvmus c.Khitit ol i nhcctnhi u i ntrnt ngdngtrns c a vo i ukhi nm tsng i nt v l ihnh nhtrnmnhnh.Tytheo m nhy uc atnhi ut icc i mtrnm tdngm sngc amnhnhs khiph cl i nh hnh nhban u.

S dngquttrongm t nhvs nhquttrong1giy cxc nhd atrn2tiuchu ntruy nhnh:

Dng n

Dng 1

Dng 2

Dng n

Dng 1

Dng 2Khungnh
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- OIRT(InternationalRadio-TelevisionOrganisation):ltiuchu ntruy n

hnh chuu,trong qui nhs dngqutl625dngvs nh/s~25 nh.

-FCC (Federal Communications Commssion ): l tiu chu n truy n hnh

c a M trong qui nhs dngqutl525dngvs nhquttrong1giy~30 nh.

Tuy nhin, trong th c t t ng ch t l ng c a nh ng i ta s d ng

ph ngphpqutxendng:

Hnh 4 Nguynlqutxendng mythu

Vi cqutxendng mb os dngquttrongm tgiykhngt ngnh ngs l nl pl ic accbn nht ngg p id n n mb och tl ng nhqut.

Xem mtnh mu qut:

Hnh5

Dng 3

Dng 1

Dng n
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Hnh 6 bn nh1vbn nh2II. DI TN CA TN HIU HNH

Dit nc atnhi uhnhg m2bank:- VHF(veryhighfrequency):49,75Mhz223,25Mhz- UHF(ultrahighfrequency):470Mhz958Mhz

Dot ns c atnhi uhnhthay it 30Hz n4,2Mhznn r ngc am i

knhtruy nhnhc ngr tr ngvc th ph thu cvotiuchu ntruy nhnh:

- OIRT:m iknhc r ng8Mhz

Hnh 7 D ithngc atnhi utruy nhnhOIRT- Chu nFCC:m iknhc r ng6Mhz

Hnh 8 D ithngc atnhi utruy nhnhmuFCC

Sng mangVideo

Sng mangAudio

0,7MHz 6,5MHz

6MHz

8MHz

1,25MHz

Sng mangVideo

Sng mangAudio

0,7MHz 4,5MHz

4,2MHz

6MHz

1,25MHz


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Vi tNams d ngtiuchu nOIRT(h truy nhnhmuPALD/K,chiti tph nsau),xems phnchiaccknhsngtrongdit ntruy nhnhtheoOIRT:

PALD/K(OIRT)TELEVISIONSTANDARD-CHANNELCHARTCATV MHz VIDE

SOUN

BROADCAST MHz VIDEO SOUND

0

48.5-56.5 49.75 56.25 2

470-478 471.25 477.75

0

58-66 59.25 65.75 2

478-486 479.25 485.75

0

376-84 77.25 83.75 2

3486-494 487.25 493.75

0

484-92 85.25 91.75 2

4494-502 495.25 501.75

0

592-100 93.25 99.75 2

5502-510 503.25 509.75

0

6174-182 175.25 181.75 2

6510-518 511.25 517.75

0

7182-190 183.25 189.75 2

7518-526 519.25 525.75

0

8190-198 191.25 197.75 2

8526-534 527.25 533.75

0

198-206 199.25 205.75 2

534-542 535.25 541.75

1

206-214 207.25 213.75 3

542-550 543.25 549.75

1

1214-222 215.25 221.75 3

1550-558 551.25 557.75

1

2222-230 223.25 229.75 3

2558-566 559.25 565.75

SC

- 111-119 112.25 118.75 3

566-574 567.25 573.75

SC

-2119-127 120.25 126.75 3

4574-582 575.25 581.75

SC

-3127-135 128.25 134.75 3

5582-590 583.25 589.75

SC

- 135-143 136.25 142.75 3

590-598 591.25 597.75

SC

- 143-151 144.25 150.75 3

598-606 599.25 605.75

SC

-6151-159 152.25 158.75 3

8606-614 607.25 613.75

SC

-7159-167 160.25 166.75 3

9614-622 615.25 621.75

SC

- 223-231 224.25 230.75 4

622-630 623.25 629.75

SC-11 231-239 232

.25 238.75 41 630-638 631

.25 637.75

SC-

12239-247 240.25 247.75 4

2638-646 639.25 645.75

SC-

13247-255 248.25 254.75 4

3646-654 647.25 653.75

SC-

255-263 256.25 262.75 4

654-662 655.25 661.75

SC-

15263-271 264.25 270.75 4

5662-670 663.25 669.75

SC-

271-279 272.25 278.75 4

670-678 671.25 677.75

SC-

279-287 280.25 286.7

4

678-686 679.25 685.75

SC-

287-295 288.25 294.7

4

686-694 687.25 693.75

SC-

295-303 296.25 302.7

4

694-702 695.25 701.75

SC-

303-311 304.25 310.7

5

702-710 703.25 709.75

SC-

311-319 312.25 318.7

5

710-718 711.25 717.75

CATV MHz VIDEO SOUN

BROADCAST MHz VIDEO SOUNDSC-

319-327 320.25 326.7

5

718-726 719.25 725.75

SC-

327-335 328.25 334.7

5

726-734 727.25 733.75

SC-

335-343 336.25 342.7

5

734-742 735.25 741.75

SC-

343-351 344.25 350.7

5

742-750 743.25 749.75

SC-

351-359 352.25 358.7

5

750-758 751.25 757.75

SC-

359-367 360.25 366.7

5

758-766 759.25 765.75

SC-

367-375 368.25 374.7

5

766-774 767.25 773.75

SC-

375-383 376.25 382.7

5

774-782 775.25 781.75

SC-

383-391 384.25 390.7

6

782-790 783.25 789.75

SC-

391-399 392.25 398.7

SC-

399-407 400.25 406.7SC-

407-415 408.25 414.7
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SC-

415-423 416.25 422.7

SC-

423-431 424.25 430.7SC-

431-439 432.25 438.7

SC-

439-447 440.25 446.7SC-

447-455 448.25 454.7

SC-

455-463 456.25 462.7SC-

463-471 464.25 470.7

SC-

471-479 472.25 478.7SC-

479-487 480.25 486.7SC-

487-495 488.25 494.7SC-

495-503 496.25 502.7

SC-

503-511 504.25 510.7SC-

511-519 512.25 518.7

SC-

519-527 520.25 526.7SC-

527-535 528.25 534.7

SC-

535-543 536.25 542.7SC-

543-551 544.25 550.7

SC-

551-559 552.25 558.7SC-

559-567 560.25 566.7

SC-

567-575 568.25 574.7CATV MHz VIDEO SOUN

BROADCAST MHz VIDEO SOUNDSC-

575-583 576.25 582.7

SC-

583-591 584.25 590.7SC-

591-599

592.25

598.7

SC-599-607 600.25 606.7SC-

607-615 608.25 614.7

SC-

615-623 616.25 622.7SC-

623-631 624.25 630.7

SC-

631-639 632.25 638.7SC-

639-647 640.25 646.7

SC-

647-655 648.25 654.7SC-

655-663 656.25 662.7

SC-

663-671 664.25 670.7SC-

671-679 672.25 678.7

SC-

679-687 680.25 686.7SC-

687-695 688.25 694.7

SC-

695-703 696.25 702.7SC-

703-711 704.25 710.7

SC-

711-719 712.25 718.7

SC- 719-727 720.

25 726.

7SC-

727-735 728.25 734.7SC-

735-743 736.25 742.7

SC-

743-751 744.25 750.7SC-

751-759 752.25 758.7

SC-

759-767 760.25 766.7SC-

767-775 768.25 774.7

SC-

775-783 776.25 782.7SC-

783-791 784.25 790.7

SC-

791-799 792.25 798.7

III. TN HIU TRUYN HNH:

III.1 Dng sng ca tn hiu truyn hnh en trng v truyn hnh mu:

T t c cc mu s c trong th c t u c th t o thnh t 3 thnh ph n

muc b nR(Red), G(Green)v B (Blue).Theo l thuy tv mus c,mu

sng cd a trns phatr nR,GvBv iph ntr mb ngnhau,tuynhin

th c t n u pha tr n theo cng th c ny th s hnh thnh mu xanh nh t do

s c m nh n v mu s c l khng th cnyths hnh thnhmuxanhnh t
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S

cmt

h

ca

m

tng

i

dos c mnh nv mus clkhng ng u:

Hnh9Tnhi uhnh ct orathngquah th ngth uknhvccc mbi nmu

c acccamera:

Hnh 10 Nguynlt oR,G,B

Tytheomus cc a i m nhmtnhi urac accc mbi n R,G,Bs cl nnh khc nhau.Trong truy nhnh en tr ng, tn hi u truy nhnh l tn

hi u chiY,lthnhph nt ngh pt R,G,Btheonguynlphamuvtheos c mth mus cc am tng icgitr xc nhtheocngth csau:

Y=0,59G+0,3R+0,11B

Tnhi utruy nhnhmus g mtnhi uYvhaithnhph nR-YvB-Y.Ngynay,t tc cc ipht us d ngtnhi uY,R-Y,B-Y truy n ithngtinhnh nh.T imythu,n ulmythutr ng ens thunh n3thnhph ntnhi u hnhsau l cl y1thnhph nY;n umythuhnhmus tit ol i3tnhi uR,G,Bd atrn3thnhph ntnhi uthu c.

400 440 480 520 560 600 640 680B c sng nm

UV Green Blue Red H ng ngo i
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Dng sng ca tn hiu hnh tng hp truyn hnh en trng:

Hnh 11 D ngtnhi uhnh entr ng

Tnhi uhnhtruy n itheot ngdngqut,t icu im idngm txung ngb ctruy nkmtheo chophpmythu ngb xungqutc adngk ti pv i ipht,th igianxu thi nxung ngb c nglth igianmsngphngtiai nt t imythudichuy nt cu idnghi nt itr v udngk ti p. Khi

truy nxongdngcu icngc am ibn nh,m tchu ixung ngb ctruy nkmtheo chophpmythu ngb nhk ti pv i ipht.Th i gianxu thi nc axung ngb nyc ngchnhllcsng i nt t imythudichuy nt cu imnhnh n umnhnh chu nb qutbn nhk ti p.

Dng sng ca tn hiu hnh tng hp truyn hnh mu:

Hnh 12 Tnhi uhnhmu

Xung ng bdng

M c en

M c tr ng

Tn hi u hnh c am t dng (Y)

B n nhi

B n nhi + 1

Chu i xung ngb mnh ( nh)

Tinhi u hnhc a1dng(Y,R-Y,B-Y)

Tn hi u ngb dng

M utnhi usngmangmu(burstmu):8-10chuk
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9/82



Dng tn hiu ng bmnh (nh):

Tnhi utruy nhnh en tr ngvmu cbi n i uAMbinsttr ckhi

truy n i.

III.2 Tn hiu m thanh trong truyn hnh:Trongk thu ttruy nhnh,mthanhstereo ctruy n icng lcv ihnhnh v c bi n i u FM t i t n s sng mang l n h n t n s sng mang

hnh6,5Mhz(OIRT)ho c4,5Mhz(FCC)III.3 S khi qu trnh thnh lp tn hiu truyn hnh:

Hnh 13 S thnhl ptnhi utruy nhnhmu

DAO NG T O S NG

MANG MU

CAMERA

M chMa

Tr n

M cht ng

h pmu

Bini u tn

hi u muT ng h p tnhi u Y

B C NG TNHI U T NG H P

M CH PHT TN

HI U NG B

B C NG TN

HI U NG B

BIN I U AMBIN ST T I F0

B C NG AUDIOV VIDEO CNG SU T PHT

BIN I U FMT I F0 + 6,5M/4,5MMICRO

ANTENPHT

Tn hi u t ng h p

Y + A + B

R G B R-Y

B-Y

A

B

AB

Y
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10/82



IV. HTHNG TRUYN HNH MU:

IV.1 H thng truyn hnh mu NTSC(NationalTelevisonSystem Committee)

L h th ng truy n hnh mu u tin trn th gi i xu t hi n t iM vo nh ng

n m50(theotiuchu ntruy nhnhFCC). h th ngNTSC,ng itatruy n

i3tnhi umusau:

Y=0,59G+0,3R+0,11BI=0,74(R-Y)-0,27(B-Y)Q=0,48(R-Y)+0,41(B-Y)

Tnhi uI ctruy nv id ithngkho ng1,3MHz,tnhi uQtruy nv id i

thng0,5MHzvtnhi uYv id ithng4,2MHz.Tnhi uIvQs cbi n

i uAMcnb ngv it ns sngmangph fsc =3,58Mhztr ckhi ctr n

v itnhi uY:


11/82



Hnh 14 S kh iphtNTSC

Dng sng ca phng php iu bin nn:

Gi i i uch i ubincnb ng cth chi nb ngcchnhntnhi u

i u bincnb ngv im tthnhph ntnhi uccngt ns vphav isng

mangg cvl ch thng(LPF) thu ctnhi ug c,chnhvldonym

myphthnh ph itruy nkmtheoccm usngmangmu(burstmu)

gipmythucc s tit osngmangph .

BngtncahtruynhnhmuNTSCtheotiuchunFCC:

uim:h thngNTSC ngi n,thi tb mhavgi imkhngph ct pvdo githnhthi tb th p.

Khuytim:d saimudod it nc aIvQkhcnhauvdos b t ix ng

c abint ntnhi uI.


12/82



IV.2 H thng truyn hnh mu PAL (PhaseAlternativeLine)

M tvin msaukhih NTSC avos d ng,h truy nhnhmuc aChu

ub t uphttri nvk th athnhqu c aNTSC aram th th ng

truy n hnhchoringmnhlh PAL.Trongh nys d ng3tnhi umusau:

Y = 0, 59G+0, 3R +0,11BU= 0,493(B-Y)V = 0, 877(R -Y)

S khcnhauquan tr ngnh tc a h PAL so v i h NTSC l tnhi uV o

phatheot ngdngqutc a nh(th hi nb ngd u bi uth c).M c ch

c as o pha ny l s a mo pha cc dng qut, v i u ny c th d n

ns mos c c amu.

Trongtruy nhnhPAL,tnhi uUvV c i ubinnnt it ns 4.43Mhz


13/82



Hnh 15 S kh iphtPAL

Di tn ca mt knh truyn hnh OIRT sdng h thng mu PAL:

IV. 3 H thng truyn hnh mu SECAM:SECAM (Sequentiel CouluerAMemoire): H th ng truy n hnh l n

l t, c nh ,ra it iPhp, cs d ngph bi nt iPhpvccn c

thu cLinxc .

H truy nhnhnys d ng3tnhi umu:

R

G

B

M CHMA

TR N

Khu ch iV(0-1,5Mhz)

i u bin nnTn hi u V

Khu ch iYDy tr

Khu ch iU(0-1,5Mhz)

i u bin nnTn hi u U

Cng

Cng

Y

V

U

OUT

OSC

4,43Mhz

+90

+90

CM T

+135

+135

C p xung

ng b

CM T

Sngmang

Video

Sngmang

Audio6,5MHz

8MHz

0,75MHz

1,25MHz4,43MHz

Y C


14/82



Y= 0,59G + 0,3R + 0,11BDR =-1,9(R-Y)

DB =1,5(B-Y)Haitnhi uDR vDB c i ut nb i2t ns sngmangmukhcnhauv

cl nl ttruy n itheot ngdng,dngth nh tg mYvDR thdngti ptheos lYvDB

Hnh 16 S kh iphtSECAM

Di tn ca knh truyn hnh OIRT h SECAM:

R

G

B

M CHMA

TR N

M ch t o xungng b

OSC4,406MHz

OSC4,25MHz

L c0-1,5MHz

Bi n i uFM

Dy tr +

+

+

opha

OUTY

DR

DB

CM T

CM T

Sng mangVideo

Sng mangAudio

6,5MHz

8MHz

1,25MHz

0,75MHz

4MHz

CY
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15/82



Ccthngskthutcbnca3hthngtruynhnhmu:

Thng NTSC PAL SECAM

Sdngqut 525 625 625

Tlqutcchdng 2:1 2:1 2:1

Tn qutmnh fV 59,94 50 50

fH (Hz) 15.734,266 15625 15625

DithngtnhiuY(MHz) 4,2 6,5 6,5

Tn ngmangmu 3.5795Hz 4,433619 DB=4,25

DR=4,40625

Dithngtnhiumu I=1,3Q=0,5

U=1,5V=1,5

DR=DB=1,5

Chng II. NGUYN L THU HNH:I. CU TO BNG N HNH (CRT: CATHOD RAY TUBE):

Hnh 17 C ut o nhnhL1:l i i ukhi n, i ukhi ns l ngtia i nt phtrat Cathoddichuy nnmnhnhL2:l igiat c,t ngt ccc i nt khichngdichuy nL3:l ih it ,h it chmtia i nt pt ptrungvom t i m nh(R,

R G B R G B R

R G B

HV

Yoke Anode

L1 L2 L3

Cu n gia nhi t

R

G

B
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16/82



G, B)R, G, B: l 3 cathod c a n hnh c i u khi n b i cc tn hi u R, G v

bnh n c t ipht.Tnhi u R, G, B nh n ccng l n th i np t i

R,G,Bcng m.

Yoke:cu nl chd c,ngang, c i ukhi nb i2dng i nhnhr ngc ac

nhi mv t o ra t tr ng theo ph ng th ng ng (cu n l ch d c) v theo

ph ngngang. D ngtnhi unh sau:

- FCC:TH =63,5s(fH =15750Hz);TH =16668,75s(fV =60Hz)

- OIRT:TH =64s(fH =15625Hz);TH =20000s(fV =50Hz)

Doc ng tia i nt suygi mtheokho ngcchtruy nnncs khcnhau

TvTh
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17/82



trongvi c i ukhi nc ng tiaquttrongmnhnhcongvmnhnhph ng1. Mn hnh phng:Mn hnh ph ng hay cn g i l siu ph ng th c ch t c ng l n hnh chn

khng gi ng nh n PIL hay trinitron, nh ng do kch th c mn hnh l n vph ng nn nh ng vng bin ngoi cng c a n hnh kho ng cch n cat t s

l n h n so v i cc i m n tm mn hnh, do v y cc i n t ph i i m t qungng di h n nn tc ng vo mn hu nh quang y u h n, k t qu l nh ng

vng bin xung quanh mn hnh, nt v sng km h n.kh c ph c hi n t ng ny, trong cc my thu mn hnh ph ng ph i s d ng

mch b in p hi t l:M ch h i t t ng (Dynamic Focus)M ch tinh ch nh i n t ng.

Cc m ch ny u s d ng k t h p b n cu n dy nh t trn c n hnh, g nca t t. i n p cung c p cho m ch ny l +15v l y t cu n cao p.

Trong my thu hnh mu SONY WEGA cn dng m ch i u ch t c tia i n

t nh m t ng c ng s c nt c a hnh nh b ng cch thay i t c tia i n tt i cc vng bin chuy n ti p t ng t hnh nh t m c en sang m c tr ng vng c l i.

Tn hi u i u ch t c c l y t tn hi u Video, qua m ch x l r i cungc p cho cu n i u ch t c trn c n hnh.

M ch i u ch t c c tc d ng t ng nt khi hnh nh chuy n t tr ng sangen v gi m nt khi chuy n c nh t en sang tr ng, sau t ng t t ng t c

cc tia i n t , k t qu l nt khi chuy n c nh en tr ng c t ng ln.Mn hnh phng v tm hin thphngCh l m t s mn hnh c g i l c mn ph ng. v n l cc CRT v i

b m t ph ng khc v i cc lo i c b m t h i cong. Cn LCD c mang tn t mhi n th ph ng.2. Mn hnh tinh th lng:Nhi m v c a mn hnh l ti t o l i hnh nh. ti t o l i hnh nh, ph ngphp ph bi n nh t hi n nay l hi n th hnh nh d a vo b n ma tr n i mnh. Theo ph ng php ny, m t khung hnh s c chia ra lm v s cc i mnh nh . Cc i m nh c d ng hnh vung, c kch th c r t nh . Kch th cth c c a m t i m nh l: 0.01x0.01 (cm). Tuy nhin kch th c th c ny

ph n l n ch c ngh a l thuy t, v h u nh chng ta t khi quan st c cci m nh t i kch th c th c c a chng, m t ph n do chng qu b, m t ph n do

kch th c quan st c a i m nh ph thu c vo phn gi i: v i cng m t di ntch hi n th , phn gi i (s l ng i m nh) cng l n th kch th c quan st

c c a chng cng b. Kch th c c a m t khung hnh c cho b i s l ngi m nh theo chi u ngang v s l ng i m nh theo chi u d c. V d kch

th c khung hnh 1600x1200 (pixel) c ngh a khung hnh s c hi n b b i1600 i m nh theo chi u ngang v 1200 i m nh theo chi u d c. Nhi u ng il m t ng gi tr 1600x1200 trn chnh l phn gi i c a hnh nh. Th c ch t,gi tr v s l ng pixel ch mang ngh a kch th c (image dimension), cn
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18/82



phn gi i (resolution) c cho b i s l ng i m nh hi n th trn di n tch m tinch vung. phn gi i cng cao, hnh nh c hi n th s cng nt. phngi i t n gi tr phn gi i th c khi m m t pixel c hi n th v i ngkch th c th c c a n (kch th c th c c a pixel c l y sao cho m tkho ng cch nh t nh, pixel c nhn d i m t gc x p x b ng n ng su t

phn li c a m t ng i). N u phn gi i b h n gi tr phn gi i th c, m tng i s c c m gic hnh nh b s n, khng nt. N u phn gi i cao h nphn gi i th c, trn l thuy t, nt v chi ti t c a hnh nh s t ng ln, tuynhin th c s m t ng i khng c m nh n c hon ton s khc bi t ny.M t ng i c m nh n hnh nh d a vo hai y u t , mu s c v sng (chi) c ahnh nh. Mn hnh mu n hi n th c hnh nh th c ng ph i ti t o l i chai y u t th gic ny c a hnh nh. V mu s c, m t ng i c kh n ng c mnh n h n 4 t s c mu khc nhau, trong c m t ph mu kho ng h n 30tri u mu c c m nh n r r t nh t. Mu n ti t o l i hnh nh chn th c, mnhnh hi n th c n ph i c kh n ng hi n th t nh t l kho ng 16 tri u mu. Bnh

th ng, khi mu n t o ra m t mu s c, ng i ta s d ng k thu t l c mu t nhsng tr ng, m i b l c mu s cho ra m t mu. Tuy nhin, v i kch th c vcng b c a i m nh, vi c t 16 tri u b l c mu tr c m t i m nh l g nnh v v ng. Chnh v th , hi n th mu s c m t cch n gi n nh ng v ncung c p kh y d i mu, ng i ta s d ng ph ng php ph i h p mu tcc mu c b n. H cc mu c b n ph i tho mn i u ki n ti t o c m tph mu r ng t cc mu thnh ph n, v cc mu thnh ph n, khi c t ng h pv i cng t l ph i t o ra m t trong hai mu s c p l mu en (lo i tr c a t t cmu s c) ho c mu tr ng (t ng ho c a t t c mu s c).V cc mu c b n, trong cc ti li u m thu t c i n th ng c p n ba

mu c b n vng, , xanh lam. Mu h p v i mu vng s t o ra mu da cam,mu xanh v i t o ra mu tm, mu vng v i xanh t o ra xanh l. Ti p t c tcc mu trn, ph i h p v i nhau s ra c t t c cc mu khc. Tuy nhin, h 3mu c b n c a m thu t c i n ngy nay t ra c nhi u nh c i m trongcc ng d ng k thu t. Th nh t, v i m i l n ph i h p mu, mu thu cth ng b x n i, gy kh kh n trong vi c ti t o l i nh ng mu s c t i nhxanh l m , vng chanh..., v nh c i m quan tr ng nh t, khi ch ng ba mu cb n vng, , xanh lam v i c ng gi ng nhau ln nhau th khng thu cmu en hon ton. Y u i m ny khi n cho h mu , vng, xanh lam bygi ch cn t n t i trong sch v , v h u nh khng c m t ng d ng k thu tth c t no. Thay vo , ngy nay c hai h mu c s d ng r t ph bi n lh mu RGB v h mu CMYK. C s xy d ng nn hai h mu c b n nyd a trn nguyn l ph i mu pht x v ph i mu h p th c a nh sng.V hai nguyn l ph i mu trn, c n ni qua v c ch m t c m nh n mu. Mus c m m t c m nh n c ph thu c vo b c sng c a nh sng chi u t i m t.B c sng c a nh sng chi u t i m t l i ph thu c vo b n ch t ngu n sng. Chai lo i ngu n sng, l ngu n sng s c p v ngu n sng th c p. Ngu n sngs c p l cc ngu n sng c kh n ng t pht ra sng nh sng, cn ngu n sng
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th c p l ngu n sng pht ra nh sng b ng cch ph n x l i nh sng t ngu nsng s c p. Khi quan st m t ngu n sng s c p, mu s c m m t ng i quanst c chnh l mu c a nh sng m ngu n sng pht ra, cn khi quan stngu n sng th c p, mu s c quan st c l mu m ngu n sng th c pkhng c kh n ng h p th t ngu n sng s c p. V d : khi quan st nh sng

pht ra t n led, chng ta c c m nh n mu th nh sng t n led phtra c b c sng n m trong vng nh sng . Cn khi quan st m t t m b ngmu , ta c c m nh n mu b i t m b ng h p th h u h t cc b c sngkhc (xanh, tm, vng...) t ngu n sng s c p, ch c mu l khng h p th

c v truy n n m t chng ta. Mu s c c a ngu n sng s c p lun khngi, cn mu s c c a ngu n sng th c p l i thay i ph thu c vo mu s c c a

ngu n sng s c p. Chi u sng ngu n sng th c p b ng cc ngu n sng s c pc mu khc nhau s thu c nh sng th c p khc nhau.Ph i mu pht x l hnh th c ph i mu s d ng cho cc ngu n sng s c p, cnph i mu h p th l hnh th c ph i mu s d ng cho cc ngu n sng th c p.

Chng khc nhau c b n: c ch c a ph i mu pht x l c ng mu, cn c chc a ph i mu h p th l tr mu. C th ki m ch ng i u ny m t cch ngi n: theo nh ngh a, nh sng tr ng l t ng ho c a v s nh sng n s c cmu s c khc nhau, c b c sng t 0.4 n 0.7um. Tuy nhin, chng ta ch cth thu c nh sng tr ng n u chi u cc chm sng ch ng ln nhau (cc chmsng c pht ra t cc ngu n sng s c p), cn n u ch ng cc mu s c lnnhau b ng cch t chng ln m t t gi y, t t nhin s ch ng bao gi nh n cmu tr ng, m ng c l i, cn ra mu en. L do l qu trnh t mu s c ln tgi y khng ph i qu trnh t ng h p cc mu, m ng c l i, l qu trnh lo itr cc mu. Khi o i tr h t t t c cc mu th r rng ch cn mu en.

Minh ho nguyn tc phi mu pht x Minh ho nguyn tc phi mu hp th

Ph i mu pht x c s d ng trong cc thi t b pht ra nh sng nh cc lo in, cc lo i mn hnh. Cc nh sng c mu khc nhau, khi chi u ch ng ln

nhau s t o ra nh sng c mu s c khc. Ba mu c b n c a c ch ph i mupht x trong cc mn hnh l mu , xanh lam v xanh l (RGB). Theo hnhtrn, s k t h p mu s c c v h i l : mu c ng mu xanh l l i ra mu vng? C n ch , nguyn l ph i mu pht x ch ng khi c quan st tr c ti p tcc ngu n sng s c p nh mn hnh, n, cn khi quan st qu trnh ph i mu


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trn gi y ho c trn mn chi u, th c ch t chng ta ang quan st m t ngu n sngth c p nn hi n nhin nguyn l ph i mu pht x trng kh v l. T ng hoc a ba mu c b n trong ph i mu pht x l mu tr ng. Ph i mu h p th cs d ng trong cc ng d ng m con ng i ph i quan st cc ngu n sng th c p,nh in bo, v tranh... Nguyn l c a ph i mu h p th l tr mu. L p v t li u

s h p th t t c cc mu s c, ngo i tr mu , nn chng ta nhn c mu. Ph i mu h p th d a trn 4 mu c b n: CMYK: vng, xanh l , h ng, en.

V l thuy t, ch c n ba mu vng, xanh l , h ng l c th t o ra d i mu khtrung th c. Sau ny, trong k thu t in n, mu en c thm vo c th i uch nh m t cch chi ti t h n sng t i c a mu. C th th y ng d ng c a hmu CMYK trong cc my in mu: chng ch c 4 h p m c, t ng ng v i 4mu ny c th in ra t t c cc mu s c c a b c tranh.Nh v y, c ch ph i mu trong cc mn hnh l c ch ph i mu pht x , d atrn ba mu c b n l mu , xanh lam, xanh l. D a trn ba mu ny, mnhnh c th ti t o l i g n nh ton b d i mu s c m m t ng i c m nh n c.

l v mu s c, cn y u t th hai c a hnh nh l sng, s c i u ch nhb i m t n n n.

Mn hnh LCD

Do hnh nh c m ho v hi n th d i d ng b n ma tr n i m nh, nnmn hnh LCD c ng ph i c c u t o t cc i m nh. M i i m nh trn mn

hnh LCD s hi n th m t i m nh c a khung hnh. Trong m i i m nh trnmn hnh LCD, c ba i m nh con (subpixel), m i i m nh hi n th m t trongba mu: , xanh l, xanh lam. n m c nguyn l ho t ng c a mn hnhLCD, ta xt m t s khi ni m sau:

nh sng phn c c: theo l thuy t sng nh sng c a Huyghen, Fresnel vMaxwell, nh sng l m t lo i sng i n t truy n trong khng gian theo th igian. Ph ng dao ng c a sng nh sng l ph ng dao ng c a t tr ng v

i n tr ng (vung gc v i nhau). D c theo ph ng truy n sng, ph ng dao


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ng c a nh sng c th l ch nhau m t gc tu . Xt t ng qut, nh sng bnhth ng c v s ph ng dao ng khc nhau. nh sng phn c c l nh sng chc m t ph ng dao ng duy nh t, g i l ph ng phn c c.

Knh l c phn c c: l lo i v t li u ch cho nh sng phn c c i qua. L p v tli u phn c c c m t ph ng c bi t g i l quang tr c phn c c. nh sng c

ph ng dao ng trng v i quang tr c phn c c s truy n ton b qua knh l cphn c c. nh sng c ph ng dao ng vung gc v i quang tr c phn c c sb ch n l i. nh sng c ph ng dao ng h p v i quang tr c phn c c m t gc0<


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quang i n v m u nguyn t Bo. Bn trong n xenon l hai b n i n c c, ttrong kh tr xenon trong m t bnh thu tinh th ch anh. Khi ng ngu n, c p chohai i n c c m t i n p r t l n, c 25 000V. i n p ny v t ng ng i n p

nh th ng c a xenon v gy ra hi n t ng phng i n gi a hai i n c c. Tia l ai n s kch thch cc nguyn t xenon ln m c n ng l ng cao, sau chng s

t ng nh y xu ng m c n ng l ng th p v pht ra nh sng theo nh lu t b cx i n t . i n p cung c p cho n xenon ph i r t l n, th nh t v t quang ng i n p nh th ng sinh ra tia l a i n, th hai kch thch ccnguyn t kh tr ln m c n ng l ng cao nh sng do chng pht ra khiquay tr l i m c n ng l ng th p c b c sng ng n.L p th hai l l p knh l c phn c c c quang tr c phn c c d c, k n l m tl p tinh th l ng c k p ch t gi a hai t m thu tinh m ng, ti p theo l l pknh l c phn c c c quang tr c phn c c ngang. M t trong c a hai t m thutinh k p tinh th l ng c ph m t l p cc i n c c trong su t. Ta xt nguyn lho t ng c a mn hnh LCD v i m t i m nh con: nh sng i ra t n n n l

nh sng tr ng, c v s ph ng phn c c. Sau khi truy n qua knh l c phn c cth nh t, ch cn l i nh sng c ph ng phn c c d c. nh sng phn c c nyti p t c truy n qua l p tinh th l ng. N u gi a hai u l p tinh th l ng khng

c t m t i n p, cc phn t tinh th l ng s tr ng thi t do, nh sngtruy n qua s khng b thay i ph ng phn c c. nh sng c ph ng phn c cd c truy n t i l p knh l c th hai c quang tr c phn c c ngang s b ch n l ihon ton. Lc ny, i m nh tr ng thi t t.

Cu to mtim nh con

N u t m t i n p gi a hai u l p tinh th l ng, cc phn t s lin k t vxo n l i v i nhau. nh sng truy n qua l p tinh th l ng c t i n p s bthay i ph ng phn c c. nh sng sau khi b thay i ph ng phn c c b il p tinh th l ng truy n n knh l c phn c c th hai v truy n qua c m tph n. Lc ny, i m nh c b t sng. C ng sng c a i m nh ph thu cvo l ng nh sng truy n qua knh l c phn c c th hai. L ng nh sng nyl i ph thu c vo gc gi a ph ng phn c c v quang tr c phn c c. Gc ny l i


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ph thu c vo xo n c a cc phn t tinh th l ng. xo n c a cc phn ttinh th l ng ph thu c vo i n p t vo hai u tinh th l ng. Nh v y, cth i u ch nh c ng sng t i m t i m nh b ng cch i u ch nh i n p tvo hai u l p tinh th l ng. Tr c m i i m nh con c m t knh l c mu, chonh sng ra mu , xanh l v xanh lam.V i m t i m nh, tu thu c vo

c ng nh sng t ng i c a ba i m nh con, d a vo nguyn t c ph i mupht x , i m nh s c m t mu nh t nh. Khi mu n thay i mu s c c a m t

i m nh, ta thay i c ng sng t i c a ba i m nh con so v i nhau.Mu n thay i sng t i ny, ph i thay i sng c a t ng i m nh con,b ng cch thay i i n p t ln hai u l p tinh th l ng. M t nh c i m c amn hnh tinh th l ng, chnh l t n t i m t kho ng th i gian m t i m nhchuy n t mu ny sang mu khc (th i gian p ng response time). N u th igian p ng qu cao c th gy nn hi n t ng bng ma v i m t s c nh c t c

thay i khung hnh l n. Kho ng th i gian ny sinh ra do sau khi i n p tln hai u l p tinh th l ng oc thay i, tinh th l ng ph i m t m t kho ng

th i gian m i c th chuy n t tr ng thi xo n ng v i i n p c sang tr ng thixo n ng v i i n p m i. Thng qua vi c ti t o l i mu s c c a t ng i m nh, chng ta c th ti t o l i ton b hnh nh.

3. Mn hnh Plasma

Plasma: Plasma l m t trong cc pha (tr ng thi) c a v t ch t. tr ng thiplasma, v t ch t b ion ho r t m nh, ph n l n cc phn t ho c nguyn t chcn l i h t nhn, cc electron chuy n ng t ng i t do gi a cc h t nhn.

ng d ng c tnh ny c a plasma, ng i ta ch t o ra mn hnh plasma.tr ng thi bnh th ng, cc ion d ng v electron chuy n ng h n lo n. V n

t c t ng i c a chng so v i nhau khng l n. Khi t kh plasma vo gi a haii n c c, i n tr ng tc d ng ln cc h t mang i n s lm cho chng chuy n

ng c h ng: cc electron b ht v pha c c d ng, cc ion d ng b ht vpha c c m. Trong qu trnh chuy n ng ng c chi u nhau nh v y, cc h tmang i n va ch m vo nhau v i v n t c t ng i r t l n. Va ch m s truy nn ng l ng cho cc electron l p ngoi cng c a nguyn t kh, lm cho cc


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electron ny nh y ln m c n ng l ng cao h n, sau m t kho ng th i gian r tng n, cc electron s t ng chuy n xu ng m c n ng l ng th p h n v sinh ram t photon nh sng theo nh lu t b c x i n t . Trong mn hnh plasma,ng i ta s d ng kh xenon ho c kh neon. Cc ch t kh ny khi b kch thch spht ra tia c c tm, khng nhn c tr c ti p b ng m t th ng, nh ng c th

gin ti p t o ra nh sng kh ki n.

C ng gi ng nh mn hnh LCD, mn hnh Plasma c ng c c u t o t cc i mnh, trong m i i m nh c ng c ba i m nh con th hi n ba mu , xanh l,

xanh lam. M i i m nh l m t bu ng kn, trong c ch a ch t kh xenon ho cneon. T i m t tr c c a bu ng c ph l p pht pho. T i hai u bu ng kh c ng

c hai i n c c. Khi c i n p c t vo hai i n c c, ch t kh bn trongbu ng kn s b ion ho, cc nguyn t b kch thch v pht ra tia c c tm. Tiac c tm ny p vo l p pht pho ph trn m t tr c c a bu ng kn s kch thchch t pht pho, lm cho chng pht sng. nh sng pht ra s i qua l p knh l cmu t tr c m i bu ng kn v cho ra m t trong ba mu c b n: , xanh l,xanh lam. Ph i h p c a ba nh sng ny t ba i m nh con trong m i i m anhs cho ra mu s c c a i m nh. Nh c i m ch y u c a mn hnh Plasma sov i mn hnh LCD l chng khng hi n th c m t phn gi i cao nh mnhnh LCD c cng kch th c. i u ny do trong mn hnh LCD, m i i m nhcon ch c n m t l p tinh th l ng kh b c ng c th thay i ph ng phn c cc a nh sng m t cch d dng, t t o i u ki n ch t o cc i m nh v ikch th c b, t o nn m t s l ng l n i m nh trn m t n v di n tch (phn gi i cao). Cn v i mn hnh Plasma, m i i m nh con th c ch t l m tbu ng kn ch a kh. Th tch c a l ng kh ch a trong m t bu ng kn ny ph i

t m t gi tr nh t nh c th pht ra b c x t ngo i m nh khi b kchthch ln tr ng thi plasma. Chnh v th , kch th c m t i m nh c a mn hnhPlasma kh l n so v i m t i m nh c a mn hnh LCD, d n n vi c v i cng


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m t di n tch hi n th , s l ng i m nh c a mn hnh Plasma t h n LCD,ng ngh a v i phn gi i th p h n.

Mn hnh thh mi: LED display v Laser TVN u nh kho ng vi n m tr c y, mn hnh tinh th l ng v mn hnh Plasma

c coi l hai nh d ng mn hnh th h m i, thay th cho mn hnh CRT qu c k . So v i mn hnh CRT, mn hnh tinh th l ng v plasma c nh ng u

i m v t tr i: kch th c nh g n, ki u dng n t ng, thi t k t m ph ng, vc th ch t o c nh ng mn hnh v i kch th c kh ng l . Mn hnh tinh thl ng, plasma, k t h p v i cng ngh truy n hnh nt cao HDTV ang m ram t k nguyn m i trong l nh v c nghe nhn, gi i tr. Nh ng, khng d ng l i

, trong khi mn hnh tinh th l ng v plasma ang t ng b c chi m l nh thtr ng, th tin t c v nh ng th h mn hnh m i, v i u i m v t tr i h n xu t hi n. Mn hnh LED v Laser ang c coi l hai nh d ng mn hnh thh m i, sau k nguyn LCD v Plasma.

Chi m u th so v i mn hnh CRT truy n th ng b i nhi u u i m, nh ng mnhnh LCD v Plasma c ng c nh ng nh c i m khng th ch i ci. Th i gianp ng, gc nhn v t ng ph n lun l i m y u ch t ng i c a mn hnh

LCD trong b t c cu c c nh tranh no v i nh ng lo i mn hnh khc. M c dcng ngh s n xu t t m panel mn hnh ngy cng pht tri n, nh ng do c tnhk thu t c a mn hnh LCD, s khng c m t c i ti n no c th xo b honton nh ng nh c i m c a lo i mn hnh ny. V i mn hnh plasma, phngi i, kh kh n khi s n xu t nh ng mn hnh kch th c b, gi thnh cao lnh ng nh c i m l n. M t cch t ng qut, t i m ng ho cao c p, mn hnhtinh th l ng v plasma v n ch a th cung c p m t ch t l ng hnh nh, chn

th c mu s c nh nh ng mn hnh CRT truy n th ng.nh vo nh ng i m y u c a, mn hnh LED v Laser ra i, k t h p cu i m c a mn hnh tinh th l ng, plasma l kch th c nh g n, ki u dngp, v c a mn hnh CRT l ch t l ng hnh nh tuy t h o.

Nh c i m c a mn hnh LCD v Plasma, b t ngu n t chnh c u t o c a hailo i mn hnh ny. t o ra c mu s c t i m i i m nh, c n ph i t ng h pmu s c t ba i m nh con. Mu s c c a ba i m nh con ny c c nh l cmu t nh sng tr ng pht ra t n n n. Vi c l c c chnh xc ba mu xanhl, xanh lam, l khng h d dng. R t kh ch t o c nh ng knh l cmu hon h o, c th l c c ton b nh sng, ch cho m t nh sng n s c

i qua. Bao gi c ng c m t l ng nh nh ng nh sng n s c c mu khc l tqua c knh l c mu. Chnh nh ng nh sng l t qua ngoi mong mu n nykhi n cho mu s c c a m i i m nh con khng t chnh xc tuy t i, d n

n vi c hi n th mu s c t i i m nh c ng khng chnh xc. H n n a, nh ci m ny cn khi n ph mu m mn hnh LCD cng v i Plasma c kh n ng ti

t o l khng l n. M t mn hnh LCD v i panel TN ch c kh n ng hi n th th c262 000 mu s c, ngay c v i panel PVA cao c p, c ng ch hi n th c 16.7tri u mu. So v i ph mu m m t ng i c m nh n c, kh n ng hi n th mu


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s c c a mn hnh LCD v Plasma ch t 35-40%.Hai lo i mn hnh th h m i, LED v Laser, v c u t o chung c ng t ng tnh mn hnh LCD v Plasma, bao g m cc i m nh, m i i m nh c ng c ba

i m nh con, m i i m nh con hi n th m t mu c b n trong h mu RGB.Tuy nhin, khc v i mn hnh tinh th l ng v plasma, mn hnh LED v Laser

khng s d ng ph ng php l c nh sng t nh sng n n n cho ra nhsng n s c, m s d ng ph ng pht pht tr c ti p ra nh sng c b c sngmong mu n. Nh vi c pht ra tr c ti p nh sng n s c, m i i m nh con scho ra m t mu s c chnh xc, v mu s c t ng h p hi n th t i m i i m nhc ng chnh xc. Mn hnh LED v Laser ang trong giai o n nghin c u nnh u nh r t t nh s n xu t cng b cc c tnh k thu t, nguyn l chi ti t,nh ng v c b n c th phn tch ho t ng c a hai lo i mn hnh trn nh sau:

Mn hnh LEDMn hnh LED, hi n ang c h tr pht tri n b i t p on Samsung. LED

Light emitting Diode, it pht quang, l m t lo i i t bn d n c kh n ng phtra nh sng kh ki n, c ng nh cc lo i b c x h ng ngo i v t ngo i. C u t oc a LED g m hai kh i bn d n, m t kh i lo i p, v m t kh i lo i n ghp v inhau. Khi t m t i n p thu n vo hai u LED, l tr ng trong kh i bn d n pv electron trong kh i bn d n n chuy n ng v pha nhau. T i m t ti p xc x yra m t s t ng tc gi a l tr ng v electron. Trong qu trnh t ng tc ny cth gi i phng n ng l ng d i d ng nh sng kh ki n ho c cc b c x i n tkhc nh tia h ng ngo i, t ngo i. B c sng c a nh sng kh ki n pht ra phthu c vo m c n ng l ng c gi i phng. M c n ng l ng c gi i phngph thu c vo c u trc nguyn t c a ch t lm bn d n. Ngy nay, nh nghin

c u v v t li u bn d n, con ng i c th ch t o c nh ng LED c kh n ngpht ra mu s c nh mong mu n, trong c ba mu c b n c a h mu RGB lxanh, xanh l, .

ng d ng LED trong vi c s n xu t mn hnh, m i i m nh s c c u t o t


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ba LED: xanh, xanh l, . Nh i u ch nh c ng sng c a t ng LED, c ththay i c ng sng t i c a ba LED so v i nhau, nh t o ra mu s ct ng h p t i m i i m nh. Khi mu n i m nh t t, ch c n t t ton b 3 LED lc th thu c mu en tuy t i, khng g p ph i hi n t ng mu en khngchn th c do l sng t n n n nh v i mn hnh LCD.

Mn hnh LaserMn hnh Laser ang c coi l cng ngh mn hnh th h m i nhi u tri nv ng nh t, c h tr pht tri n b i Mitsubishi. Laser l vi t t t c a c m: LightAmplification by Stimulated Emission of Radiation, khu ch i nh sng b ngcc pht x kch thch. nh sng laser pht ra c ng d a trn nguyn l b c x

i n t , tuy nhin c nhi u tnh ch t c bi t so v i nh sng thng th ng. nhsng laser c c ng m nh l laser c t o thnh t ch t r n. M t ch t r nthch h p, khi nh n c kch thch t bn ngoi, cc electron bn trong s nh yln m c n ng l ng cao h n, sau l i nhanh chng chuy n v m c n ng l ngth p h n v gi i phng m t photon nh sng. Photon ny bay ra, chuy n ng

trong lng kh i ch t r n, l i va ch m v i nh ng nguyn t khc, kch thchelectron c a nguyn t ny ln tr ng thi cao h n, sau khi nh y xu ng tr ng thith p l i ti p t c pht ra m t photon khc. C nh v y t o ra m t ph n ng dychuy n, cng ngy cng gi i phng ra nhi u photon. T i m t u c a kh i ch tr n c g n m t g ng bn m . Photon g p g ng ny s i ra ngoi, t o thnhtia Laser. Cc photon c a tia laser, do c cng t n s , cng pha, l i chuy n ngsong song v i nhau nn tia laser c n ng l ng r t l n, l i c t p trung trongm t di n tch nh . M t c i m quan tr ng c a tia laser, l cc photon c a nsinh ra t ph n ng dy chuy n, nn n ng l ng c a cc photon gi ng nhau tuy t

i, d n n b c sng c a tia laser l ng nh t tuy t i.

Laser heli-neonM t mn hnh laser, yu c u ph i c ba tia laser v i ba mu s c xanh, xanh l,

. Hi n nay, m i ch c tia laser (cn g i l laser h ng ng c) l ph bi n v


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c kh n ng ng d ng trong s n xu t mn hnh, cn laser xanh v xanh l, do cn ng l ng cao h n nn g n nh khng th t o c trong i u ki n ho t ngc a m t mn hnh. Thay vo , ph i s d ng m t qu trnh bi n i t n sthu c laser c t n s cao h n t n s c a tia laser g c. Qu trnh ny g i lSecond Harmonic Generation, l i d ng s t ng tc c a cc photon v i v t li u

phi tuy n c bi t k t h p n ng l ng vo m t photon m i, c n ng l ngg p i photon ban u, hay c b c sng nh b ng m t n a. Second HarmonicGenerationi c tm ra vo n m 1961, m t th i gian sau khi cc nh khoa h ctm c ph ng php t o ra tia laser b ng h ng ng c. Nh ph ng phpny, c th t o ra c tia laser xanh v xanh l.Mn hnh laser, v i nguyn l ho t ng d a vo vi c pht ra cc tia laser thaycho vi c dng n c ng cao (HID: high intensity discharge) trong cc mnhnh projector, c nhi u u i m so v i cc lo i mn hnh hi n nay nh c khn ng ti t o l i m t ph mu r t r ng v i chnh xc mu s c cao (c th t

n h n 90% ph mu m m t ng i c th c m nh n), tiu th t n ng l ng

h n mn hnh LCD hay Plasma, kch th c g n nh , tu i th lu (c th ln nh n 50000 gi ). Mn hnh Laser ang c nhanh chng hon thi n trong vi cnghin c u, c kh n ng s ra m t vo cu i n m 2007, v d n ph bi n vo n asau n m 2008 v u 2009. Theo d on, m t khi a vo s n xu t quy ml n, gi thnh c a mn hnh Laser s r h n r t nhi u so v i gi mn hnh LCDv Plasma hi n t i, c th ch b ng m t n a

Mn hnh SED

Mn hnh SED, m t th i gian t ng c coi l cng ngh mn hnh th hm i tri n v ng nh t, so v i cc cng ngh khc nh mn hnh Laser, mn hnhOLED... Tuy nhin, t sau n m 2004, v i v r c r i gi a nano-proprietary (hngpht minh ra cng ngh SED) v Canon (hng mua b n nguy n s n xu t mnhnh SED) do Canon t chia s cng ngh v i Toshiba, cc ho t ngnghin c u v a vo s n xu t mn hnh SED ch m h n l i. Ban u, Canon d

nh tung ra m u tr ng by chnh th c mn hnh SED vo tri n lm CES 2006 vs n xu t i tr vo cu i n m 2006, u n m 2007. Sau k ho ch ny b


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hu b . Vi c cng b mn hnh SED c d i sang tri n lm CES 2007. Tuynhin, m t n m sau, thm m t l n n a, k ho ch cng b mn hnh SED b trhon, r t ng ti c khi m cng ngh mn hnh v truy n hnh nt cao chnh ltiu i m nng nh t c a h i ch CES 2007. Mn hnh SED nh m t v th lcng ngh mn hnh th h m i tri n v ng nh t vo mn hnh Laser. Nguyn

nhn ch y u l gi c a mn hnh SED khi s n xu t hng lo t s khng th c nhtranh c trn th tr ng, sau c n s t gi m gi chng m t hai lo i mn hnhLCD v Plasma.Mn hnh SED: Surface-conduction electron-emitter display: mn hnh pht x

i n t d n b m t. Cng ngh SED th c ch t c nghin c u t r t lu, von m 1986. Ngay sau khi mn hnh CRT tr nn ph bi n, gi i khoa h c nh nra m t s i m y u c a lo i mn hnh ny, trong r r t nh t l t n s qut quth p v i m t s s n ph m c kch th c khung hnh l n. M t t ng ban u

c a ra, l s d ng nhi u sng phng i n t thay cho m t sng phngi n t c i thi n t n s qut. chnh l t ng b t ngu n cho vi c nghin

c u cng ngh mn hnh SED, m t c i ti n l n t mn hnh CRT.C u t o c b n c a mn hnh CRT bao g m m t sng phng i n t , m t hth ng t o t tr ng bi n i qu o electron, v m t mn hu nh quang. ngphng i n t d a theo hi u ng pht x nhi t electron. Khi cung c p n ng l ngcho m u kim lo i d i d ng nhi t, cc electron s c truy n n ng l ng b tra kh i lin k t m ng tinh th kim lo i. Cc electron ny sau khi b t ra c t ngt c b i m t i n tr ng. Sau khi c t ng t c b i i n tr ng, electron c qu

o th ng h ng v pha mn hu nh quang. Tr c khi p vo mn hu nhquang, electron s ph i bay qua m t vng t tr ng c t o b i hai cu n dy,m t cu n t o t tr ng ngang v m t cu n t o t tr ng d c. Tu theo c ng

c a hai t tr ng ny, qu o c a electron trong t tr ng s b l ch i v pvo mn hu nh quang t i m t i m c nh tr c. To c a i m ny trnmn hnh c th c i u khi n b i vi c i u ch nh c ng dng i n tronghai ng dy, qua i u ch nh c ng t tr ng tc d ng ln electron.Electron p vo mn hu nh quang (th ng l ZnS) s khi n i m pht sng.

t o ra ba mu c b n trong h mu RGB, ng i ta s d ng ba sng phngi n t ring, m i sng t ng ng v i m t mu.

Cng ngh mn hnh SED, v c b n kh gi ng v i mn hnh CRT, c ng d a vos pht sng c a ch t hu nh quang khi b electron p vo. Tuy nhin, mn hnhSED c m t c i ti n v t b c so v i mn hnh CRT, l thay v s d ng m tsng phng i n t i u khi n s pht sng c a ton b i m nh, mn hnhSED s d ng ring m t sng phng i n t cho t ng i m nh. V i mn hnhCRT, c th i u khi n m t chm tia electron qut kh p chi u ngang v chi ud c mn hnh, yu c u u tin l qu o c a chm tia electron trong t tr ngph i di, t ng ng v i l n c a mn hnh. i u ny gy ra nh c i m c amn hnh CRT l chi u dy qu l n. Nh c i m th hai c a mn hnh CRT, l t n s qut. Do ch v i m t chm tia electron, l i ph i qut su t ton b cc

i m nh trn mn hnh hi n th m t khung hnh, nn th i gian hi n th m t


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khung hnh s cng l n khi s i m nh cng l n. i u ny gy tr ng i cho vi cs n xu t cc mn hnh c kch th c l n. M t nh c i m n a c a mn CRT ldo chm tia electron ph i qut xung quanh m t tm, nn b m t mn hnh l bm t cong ( l h i tr c, cn gi y th c mn CRT ph ng). B ng vi c sd ng m t sng phng i n t cho m t i m nh ring bi t, mn hnh SED

kh c ph c hon ton ba nh c i m ni trn c a mn hnh CRT. Do m i i mnh c m t sng phng i n t ring, nn chm electron sau khi c t ng t c

b i i n tr ng s t i p th ng vo mn hu nh quang m khng c n bay quavng t tr ng, nn b dy c a mn hnh SED r t b, ch ngang ng a v i mnhnh LCD v Plasma. M i i m nh c i u khi n c l p b i m t sng phngnn ton b i m nh trn khung hnh s hi n th cng m t lc, t n s hi n th sl n h n nhi u so v i t n s qut c a mn hnh CRT. V cu i cng, khng h cb t c m t qu trnh "qut" no v i mn hnh SED, nn hi n nhin b m t mnhnh s l b m t ph ng. Nh v y, nh d a trn cng ngh truy n th ng c a mnhnh CRT nn mn hnh SED s c ch t l ng hnh nh ngang ng a mn hnh

CRT, tuy nhin c kch th c mn hnh l n h n, phn gi i cao h n, v nhg n h n.II. KHI CAO TN HAY KHI CHN KNHDng ch n l a knh truy n hnh c a m t i pht hnh m ta mu n thu.

Tn hi u truy n hnh a n kh i ny s c khu ch i ln r i tr n v i dao ngngo i sai c a my t o ra tn hi u trung t n th p h n, d khu ch i v ch n l c.Kh i ch n knh c 3 ph n: khu ch i cao t n, dao ng ngo i sai ( dao ng n i)v tr n t n.

1. Khi nim chungTrong my thu hnh mu, cc yu c u c bi t i kh i chon knh:

T ng khu ch i cao t n ph i c nhi u r t t, t c linh ki n c a n ph i cnhi u nh v lm vi c ng ch .

T n s c a dao ng n i c ng ph i th t n nh n u khng c th x y ra m tmu ho c mu khng trung th c ho c nhi u trn nh truy n hnh ( nhi u do phchgi a trung t n ti ng v trung t n mu)V th th ng c thm m ch t i u t n AFC

2. S khi ca b knh.

S khi ca b knh


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Mch vo : C nhi m v ch n knh theo nguyn l c ng h ng sng, t i antenc nhi u sng mang t cc i pht khc nhau i t i, sng mang no c t n s trngv i t n s dao ng c a m ch vo s c ch n i vo m ch khu ch i.cao t n. Mch K cao tn : Khu ch i sng mang t i pht sau khi c thu vo qua

m ch c ng h ng . Mch dao ng : C nhi m v t o dao ng n i a vo m ch tr n t n. Mch trn tn : C nhi m v tr n t n s dao ng v i tn hi u cao t n l y rat n s trung t n IF

IF = F0 - RFF0 : L t n s dao ng n iRF : L tn hi u cao t n ( sng mang )IF : L t n s trung t n, t n s IF c d i t n c nh t 31,5MHz n 38MHz

3. Mch vo & K. i cao tn.M ch vo th c ch t l m t b y c ng h ng, khi ta chuy n knh, cc cu n dy c

c m khng khc nhau c ti p xc vo m ch c ng h ng lm thay i t n s c ngh ng, n u t n s c ng h ng trng v i t n s sng mang th tn hi u sng mang

c thu vo v c khu ch i qua t ng Q1 , u ra t ng K cao t n Q1 c thmm t m ch c ng h ng n a nng bin tn hi u ln m c cao nh t.
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4. Mch dao ng ni

Mch to dao ng

M ch t o dao ng cung c p dao ng n i cho m ch i t n, khi ta chuy n knh,cu n L1 c thay th t o ra m ch c ng h ng c t n s thay i.

5. Mch i tn

Gii t n c a tn hi u IF

M ch i t n c tn hi u RF v t n s dao ng n i OSC cng c a vo c c Bc a n i t n, tn hi u trung t n IF l y ra trn c c C c gi tr b ng hi u hai t n s

u voIF = OSCRF

N u t n s RF t ng th t n s dao ng OSC c ng t ng t ng ng m b o t ns IF lun lun khng i, t n s trung t n IF chi m m t gi i t n t 31,5MHz n38MHz


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III. KHI TN HIU HNHC nhi m v khu ch i trung t n mang tn hi u hnh, sau tch tn hi u

hnh ra kh i trung t n hnh v khu ch i ln n m c c n thi t i u ch nhnh. Kh i tn hi u hnh g m cc t ng khu ch i trung t n hnh, tch sng th t n vcc t ng khu ch i th t n. Ngoi ra cn c b t o i n p t i u khu ch dng i ukhi n h s khu ch i c a t ng khu ch i cao t n v khu ch i trung t n hnh v im c ch gi cho m c tn hi u t thay i khi kho ng cch gi a my thu hnh v ipht hnh thay i nhi u.

1. S mch khuch i trung tn

Mch khuch i trung tn sdng IC

IC Khu ch i trung t n bao g m cc m ch .

IF AMPLY l m ch khu ch i tn hi u trung t n t b knh a sang, sau cung c p tn hi u cho m ch tch sng. Detector L m ch tch sng, tch tn hi u Video t ng h p ra kh i sng mang c ai pht, bi n p T2 c ng h ng cho m ch tch sng.

Vdeo Amply L m ch khu ch i tn hi u Video tr c khi a ra ngoiIF AGC (Auto Gain Control ) L m ch t o i n p t i u ch nh khu ch i chom ch trung t n RF AGC L m ch t o i n p t i u ch nh khu ch i cho m ch RF Amplyc a b knh M ch trung gian gi a b knh v t ng khu ch i trung t n l b l c gi i thng,m ch ny c nhi m v cho tn hi u trung t n thu c gi i 31,5MHz n 38MHz i qua


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v lo i b cc t n s ln c n, m ch ny bao g m cc linh ki n, C1,L1,C2,C3, L2, T1t o thnh cc m ch c ng h ng nng cao bin tn hi u trong d i sng trungt n, tn hi u vo c a vo cc chn 8 v 9 c a IC Tn hi u ra chn s 3 l tn hi u Video t ng h p bao g m Tn hi u th t n(Video), xung H.syn, xung V.syn, tn hi u i u t n FM.

2. Tn khuch i th tn (Video)

Nhim v ca mch khuch i th tn : Khu ch i tn hi u Video sau tch sng ln bin l n => cung c p cho nhnh ti t o l i hnh nh. Ti p nh n xung dng v xung mnh a v xo tia qut ng c Th c hi n cc ch c n ng i u ch nh t ng ph n, sng.

Tng khuch i th tn my Samsung 359R


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Nhim v cc linh kin trong mch : C1 : L t n i t ng CF1 : L th ch anh, l c tn hi u ti ng khng cho ti ng nh h ng sang nghnh n Q khu ch i tn hi u th t n, R2 l i n tr nh thin, R3 l tr ghnh, R4

l tr n nh nhi t , R5 l i n tr phn p. Tri t p Contras i u ch nh bin tn hi u ra => L tri t p ch nh t ngph n trn mn hnh Xung dng H.P (Horyontal Pul ) i qua R6 v D1, xung mnh V.B (VertBlanking) i qua R7 v D2 : hai xung cng i qua t C3 vo c c E n K th t nlm nhi m v xo tia qut ng c T C4 a tn hi u th t n vo Katt n hnh v ng n i n p m t chi u Tri t p Bright lm thay i i n p m t chi u trn Katt => L tri t p ch nhsng mn hnh

IV. KHI NG B:

1. Mch khuch i v tch xung ng bDng tch cc xung ng b ra kh i tn hi u th t n chung r i phn chia

chng ra xung ng b mnh a n ng b t ng dao ng t o sng qut mnhv xung ng b dng a n ng b t ng dao ng t o sng qut dng. Kh i

ng b g m t ng tch sng ng b , khu ch i v phn chia xung ng b , b sopha.

2. S khi ca khi ng b :

S khi ca khi ng b

Mch tch xung ng b : Tch tn hi u ng b chung ra kh i tn hi u Videot ng h p . Mch khuch i : Khu ch i bin xung ng b chung Mch tch phn : Cho tn hi u ng b mnh V.SYN i qua Mch vi phn : Cho tn hi u ng b dng H.SYN i qua


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3. S mch chi tit :

Khi ng b trong Ti vi Samsung 359R

R1, C1, R2, C2 l m ch tch xung ng b , tch hai xung V.SYN v H.SYN rakh i tn hi u Video t ng h p n Q1 l t ng khu ch i hai xung ng b trn R7, C3 v R8, C4 l hai m t l c tch phn , cho t n s th p V.SYN i qua v l cb t n s cao C5, R9 l m ch l c vi phn cho t n s cao H.SYN i qua v ng n t n s th p l i . Xung V.SYN sau m ch l c tch phn i t i m ch dao ng mnh

Xung V.SYN sau m ch vi phn i t i m ch so pha

V. KHI TO SNG QUT MNH:T o ra tn hi u qut mnh, cung c p cho cc b dy qut mng. Kh i ny

g m t ng dao ng t o sng, ti n khu ch i mnh, t ng khu ch i cng su t mnhv cc cu n qut mnh.

1. Nhim v ca khi qut mnh :Nhi m v c a kh i qut mnh l li tia i n t qut theo chi u d c, kh i qut mnh

bao g m : Mch to dao ng : T o ra xung mnh c t n s 50Hz cung c o cho t ngcng xu t Mch tin K : Khu ch i xung mnh cho kho h n tr c khi a vo t ng


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cng xu t. Tng cng xut : Khu ch i xung mnh cho l n r i a n cu n li mnh

li tia tia i n t dn theo chi u d c. Xung ng b : i u khi n cho m ch dao ng , dao ng ng t n s .

2. S chi tit khi qut mnh sdng n bn dn :

S chi tit khi qut mnh dngn bn dn.

Phn tch s mch : Q1 l t ng dao ng, ho t ng theo nguyn l dao ng ngh t, L1 l cu n dyt o dao ng, VR1 l tri t p i u ch nh t n s cn g i l tri t p V.Hold VR2 l tri t p a xung dao ng sang t ng ti n K i, khi ch nh VR2 s lmthay i bin dao ng ra => VR2 l tri t p ch nh chi u cao mn hnh. VR3 l tri t p ch nh tuy n tnh, khi ch nh VR3 th d ng xung thay i => tuy ntnh mnh thay i, tuy n tnh l dn u gi a cc i m nh theo chi u d c. Q2 l t ng ti n khu ch i , K o pha tn hi u tr c khi a vo hai n cngxu t. Q3 v Q4 l hai n K i cng xu t, m c theo ki u y ko L2 l cu n li mnh g n trn c n hnh

M ch h i ti p qua C1 c tc d ng s a mo tuy n tnh . Xung ng b mnh c a vo m t u c a cu n dy L1

3. S khi qut mnh dng IC trong Ti vi Samsung 359RPhn tch s trn : Trong IC c tch h p ba m ch : T o dao ng : V.OSC, t ng ti n K iV.Amply v t ng cng xu t V.OUT, cc linh ki n i n tr , t i n c a rangoi.


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Xung ng b V.SYN i qua m ch l c tch phn R1, C1 sau i qua t vochn s 5 => i vo m ch dao ng gim c nh t n s mnh. Chi t p V.HOLD chn 6 c tc d ng i u ch nh thay i t n s mnh. Chi t p V.SIZE chn 4 c tc d ng i u ch nh thay i kch th c d c mnhnh.

Chi t p V.LIN t sau cu n li tia c tc d ng thay i i n p h i ti p => Lmthay i tuy n tnh d c mn hnh, C3, C4 l cc t h i ti p .

VI. KHI TO QUT DNG:1. Nhim v ca khi qut dng.

T o ra tn hi u qut dng, cung c p cho cc cu n qut dng. Kh i ny g mt ng dao ng dng, t ng khu ch i trung gian v t ng khu ch i cng su t dng,bi n p ra ph i h p v i cc cu n qut dng. Ngoi ra, kh i ny cn c m ch t oqu cao p cung c p cho An t n hnh, t o cc cao p c p cho cc c c c a nhnh, t ng khu ch i cng su t mnh, khu ch i th t n cu i

1. Phn tch s khi qut dng.

S khi ca khi qut dng
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Mch so pha : So snh gi a hai t n s l xung H.syn t i pht g i t i v i xungAFC t cao p h i ti p v t o ra i n p i u khi n, n u t n s AFC b ng H.synth p i u khi n khng i => t n s qut dng khng i, n u t n s AFC > t n s

H.Syn th m ch so pha t o ra i n p i u khi n gi m => lm t n s dao ng dnggi m v ng c l i. ( AFC l vi t t t c a Auto Frequency Control : T ng i uch nh t n s dng, H.syn l vi t t t c a Horyontal Synsep : Xung ng b dng )Mch to dao ng dng : T o ra xung dng c t n s b ng 15625Hz , t n s ny

c gi c nh nh i n p i u khi n t m ch so pha, tr ng h p h ng m ch sopha ho c m t xung H.syn hay xung AFC th t n s dng bi sai => sinh hi n t ng m t ng b => nh b

xin ho c tri ngang. Tng kch dng : khu ch i xung dng cho m nh sau a t i i u khi n

n cng xu t ng m Tng cng xut : Ho t ng ch ng t m i u khi n bi n th cao pho t ng . B cao p : L bi n th ho t ng t n s cao 15625Hz cung c p cc m c i np cao cho n hnh, nh p HV = 10.000V, p G2 = 110V, v cung c p xung dngi u khi n cu n li ngang.

3. S chi tit khi qut dng my Samsung 359R
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Phn tch s chi tit : R1, R2, D1, C1 l m ch so pha, m ch ny so snh xung H.syn v xung AFC( m u tm ) t o ra i n p i u khi n i qua R3 v R4 vo i u khi n n dao

ng Q1 R3, C2 l m ch l c tch phn lo i b thnh ph n xung xoay chi u , gi l i thnhph n m t chi u Q1 l n t o dao ng, t C4 v cu n L1 t o thnh m ch dao ng LC, t C3h i ti p d ng, t n s dao ng ph thu c vo cc t C3, C4, v cu n dy L1, nmch nh H.Hold chnh l i u ch nh li cu n dy L1 => lm c m khng L1 thay i =>lm t n s dao ng thay i, t n s c n nh nh i n p i u khi n t m chso pha a sang , dao ng c l y trn chn E i qua R8 a sang t ng kch dng. Q2 l n kch dng, khu ch i xung dng ln m nh sau ghp qua bi np kch T1 sang i u khi n n cng xu t Q3 Q3 l n cng xu t, ho t ng ng t m nh m t cng t c i n t => t o ra dngi n xoay chi u ch y qua cao p T2, t C5 l t b, C6 v D3 l t v Diode nh t,

D4 v C7 l m ch ch nh l u i n p B2 =110V cung c p cho G2, C8 v D5 t o rai n p m a vo G1 khi t t my, i n p HV l y trn cu n th c p kho ng 10KVi n p ny dng v n hnh lm c c m c a t l c v v y v n hnh ph i lun

lun c ti p mass

Tng dao ng dng


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VII. KHI NG TING:

1. S khi ng ting

S khi ng ting

Tn hi u i u t n FM i cng tn hi u Video t ng h p c tch qua t gi y => iqua m ch c ng h ng u vo i vo t ng khu ch i trung t n ti ng => sau khi Kln bin l n tn hi u a sang m ch tch sng i u t n l y ra tn hi u mt n => sau tn hi u m t n c khu ch i qua m ch cng xu t r i a ra loapht l i m thanh.

2. Mch trung tn ting dng Transistor

Mch trung tn ting dng Transistor T301 l bi n p trung t n c ng h ng u vo , c ng h ng t n s 6,5MHz Q1 l n khu ch i trung t n T302 l bi n p trung t n tch sng, sau bi n p T302 l m ch tch sng i u t n n Q2 l m ch khu ch i tn hi u m t n .
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3. Khi ng ting dng IC

Khi ng ting trong Tivi Samsung 359R

CF1 l th ch anh c ng h ng u vo, c ng h ng t n s 6,5MHz IF Amply l t ng K trung t n ti ng FM DET l m ch tch sng i u t n CF2 l th ch anh c ng h ng u ra Tn hi u m t n sau tch sng c a n chi t p Volume sau a sangt ng cng xu t AUDIO OUT khu ch i v a ra loa.

VIII. KHI NGUN NUI.

1. Khi ngun n p tuyn tnhNhi m v c a kh i c p ngu n l cung c p ngu n 1chi u 12V n nh cho my

ho t ng, i n p vo l ngu n xoay chi u 220V AC khng n nh.

S khi - khi ngun nui

Bi n p c nhi m v i i n 220V AC xu ng i n p 18V AC M ch ch nh l u c u v l c ch nh l u i n p xoay chi u AC thnh i n p m tchi u DC M ch n p tuy n tnh : c nhi m v gi cho i n p ra c nh v b ng ph ngcung c p cho t i tiu th .
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Mch gim p, chnh lu v mch lc .

Bin p v mch chnh lu cu, mch lc

Bi n p ngu n : i n p vo = 220V 50Hz , i n p ra = 18V D1, D2, D3, D4 l m ch ch nh l u c u , ch nh l u i n AC thnh DC T C1 : 2200F/25V l t l c ngu n chnh

Bin p v mch chnh lu cu, mch lc trong thc t.

Mch n p tuyn tnh :Nhim v: M ch n p tuy n tnh c nhi m v => T o ra i n p u ra n nh vb ng ph ng, khng ph thu c vo i n p vo , khng ph thu c vo dng i n tiuth

S khi tng qut


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i n p vo l ngu n DC khng n nh v cn g n xoay chi u. i n p ra l ngu n DC n nh v b ng ph ng M ch l y m u l l y ra m t ph n i n p u ra, i n p l y m u t ng gi m t lv i i n p u ra . M ch t o p chu n : l t o ra m t i n p c nh

M ch d sai : so snh i n p l y m u v i i n p chu n pht hi n s bi n ii n p u ra v khu ch i thnh i n p i u khi n quay l i i u ch nh m

c a n cng xu t, n u i n p gi m th p i u khi n , i u khi n cho n cngxu t d n m nh, v ng c l i . n cng xu t : khu ch i

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