MC LC

1MC LC

2DANH MC HNH V

3T VN

4

SEQ MTSec \r 1 \h \* MERGEFORMAT

SEQ MTChap \r 1 \h \* MERGEFORMAT

CHNG ITNG QUAN V THUT TON HOUGHEquation Chapter 1 Section 1

41.1 Tng quan v phng php Hough

71.2 Cc phng php Hough

71.2.1 Phng php bin i Hough c bn (standard)

81.2.2 Phng php bin i Hough theo xc sut (Probability)

141.2.3 Phng php bin i Hough ngu nhin (Randomized Hough Transform)

161.3 nh gi cc phng php Hough

18CHNG 2 THC HIN THUT TON HOUGH TRN NN FPGA

182.1 Nguyn tc bin i Hough ng dng trn nn FPGA

192.2 Phng php tnh ton bin i Hough

192.2.1 Phng php c in

202.2.2 Bin i Hough tng cng nhanh 2 (FIHT2)

212.2.3 Phng php da trn gc nghing.

222.2.4 Thut ton CORDIC

252.3 Trin khai FPGA theo cu trc CORDIC

282.4 Kin trc FPGA thi gian thc cho bin i Hough s dng thut ton CORDIC

322.4.1 Tm ng thng

372.4.2 Nguyn mu

38KT LUN

39THAM KHO

DANH MC HNH V

5Hnh 1.1 Khng gian Hough

6Hnh 1.2. Cc mt phng trong khng gian Hough

18Hnh 2.1 Nguyn tc bin i Hough

21Hnh 2.2 Mi quan h nh hng cnh gc nghing

24Hnh 2.3 So snh kch thc khng gian tham s ca bin i Hough da trn gc nghing v c in

25Hnh 2.4 Kin trc CORDIC lp song song

26Hnh 2.5 Kin trc CORDIC song song lin tng

28Hnh 2.6 Cu trc chui CORDIC

29Hnh 2.7 Cu trc chung tm ng thng

30Hnh 2.8 Cu trc chung GradientCORDIC da trn bin i Hough

30Hnh 2.9 Kin trc n v thng s

33Hnh 2.10 Kin trc n v tham s

34Hnh 2.11 Kin trc khi xy dng li ng thng

34Hnh 2.12 Kt qu tm ng thng

36Hnh 2.13 H thng nguyn mu th nghim

T VN

Nh bit, bin i Hough (HT) c s dng rng ri trong vic x l hnh nh, c bit l trong nhn dng mu nh cc ng thng, hnh trn, hnh bu dc v cc hnh dng khc. Nguyn tc bin i Hough cng c s dng trong vic nhn ra i tng 3D, vt rn nh hng, cc thng s chuyn ng ca cc vt th di ng ... Bin i Hough l mt k thut hp dn v bn ca n vi nhiu. Tuy nhin, nhc im chnh ca n l yu cu kch thc b nh ln v cc tnh ton phc tp v tn nhiu thi gian.

Rt nhiu cng trnh c tin hnh c lin quan n vic thc hin phn cng ca bin i Hough thi gian thc. Trong chip L64250 ca Logic Company c chnh sa bin i Hough cho vic x l thi gian thc. OGorman v Clowes xut vic s dng gc nghing gim phc tp trong vic tnh ton. Ngoi ra, Zhou v Kornerup xut s dng thut ton CORDIC trong vic bin i nhanh Hough. Cc xut kin trc thi gian thc cho vic pht hin ng thng c thc hin trn cc thit b FPGA, s dng c gc nghing v thut ton CORDIC. Mt mt, gc nghing c s dng gim khi lng tnh ton thi gian yu cu t hn, mt khc thut ton CORDIC c s dng lm cho cc ton t t phc tp hn. Phn chng I trnh by nhanh nguyn tc bin i Hough v c s tho lun c lin quan n cc phng php tnh ton chuyn i Hough khc nhau. Thut ton CORDIC c m t mt cch ngn gn trong phn 2.2.4. Chi tit v mt s vic thc hin thut ton CORDIC c trnh by la chn cu trc ph hp vi kin trc ca chng ta. Phn 2.3 m t cc thut ton pht hin ng thng v cc kin trc c xut trn nn FPGA. Phn 2.4 trnh by cc h thng nguyn mu. Cui cng l cc kt qu thu c c trnh by cui bo co ny..

1.1 Tng quan v phng php Hough

Transform Hough l mt phng php ni ting pht hin i tng tham s. y l tiu chun thc t cho vic pht hin ng thng v vng trn trong b d liu 2-chiu. i vi 3D, cho n nay n c t s ch . Ngay c i vi trng hp 2D do chi ph cao tnh ton dn n s pht trin ca rt nhiu bin th cho Hough Transform. Trong bi vit ny, c s nh gi cc bin th khc nhau ca Bin i Hough c lin quan n ng dng pht hin mt phng trong nhng m my im 3D mt cch ng tin cy.

Ngoi tnh ton chi ph, vn chnh l cch biu din b tch ly. Cc trin khai thng thng thin v i tng hnh hc vi mt s thng s do khng ng u ly mu ca khng gian tham s. Ni dung trnh by mt cch tip cn thit k b tch ly tp trung vo vic t c cng kch thc cho mi cell v so snh n vi thit k hin ti.

Bin i Hough (Hough transform) l mt phng php pht hin cc i tng tham s, thng c s dng cho cc ng thng v vng trn. Tuy nhin, c th tp trung vo vic pht hin cc mt phng trong cc m my im 3D. (Mc d nhiu phng php Bin i Hough lm vic vi u vo l im nh nhng iu ny khng phi luc no cng cn thit).

Trong kch bn, c mt tp hp cc im cha c t chc c s dng nh l u vo v u ra bao gm cc tham s mt phng. Mt phng thng c biu din bi k hiu l khong cch n gc ca h ta v dc mx v my theo hng x v trc y, tng ng:

trnh cc vn do dc v hn khi c gng biu din mt phng thng ng, mt nh ngha thng thng, Hesse hnh thc bnh thng, s dng cc vect php tuyn. Do mt phng c a ra bi mt im p trn mt phng, n vector php tuyn m vung gc vi mt phng v l khong cch vi gc

Xem xt cc gc gia vector php tuyn v phi hp h thng, cc ta ca N c factorized (1)vi l gc ca vector php tuyn trn mt phng xy

l gc gia mt phng xy v vector php tuyn trong z hng nh m t trong hnh. 1. ,

c xc nh bi b tham s (, , ) trong khng gian 3 - chiu Hough (3D Hough Space)

Nh vy m mi im trong Space Hough tng ng vi mt mt phng.

Hnh 1.1 Khng gian Hough tm cc mt phng trong mt tp hp im, ta phi tnh ton Bin i Hough cho mi im. Vi mt im p trong ta Cartesian chng ta phi tm tt c cc mt phng im nm trn, ngha l, tm thy tt c cc , v p ng phng trnh (1). nh du cc im trong khng gian Hough dn n mt sinusoid 3D ng cong nh hnh. 2.

Hnh 1.2. Cc mt phng trong khng gian HoughCc nt giao ca hai ng cong Hough khng gian ch ra mt phng c th xoay xung quanh ng thng c xy dng bi hai im. Do , cc giao l ba ng cong Hough khng gian tng ng vi to cc xc nh mt phng c ko di bi ba im. Trong hnh. 2 - giao nhau c nh du mu en. Vi b im P trong h ta Carter, mt trong nhng bin i tt c cc im pi P thnh Hough Space. Cng c thm cc ng cong giao nhau trong hj (, , ), cng c nhiu im nm trn mt phng biu din bi hj v xc sut hj thc s l chit xut t P cng cao hn.

1.2 Cc phng php Hough

1.2.1 Phng php bin i Hough c bn (standard)

i vi cc ng dng thc t, Duda v Hart (1971) xut s dng khng gian Hough vi cc tham s , v dng biu th mc ca mi cell theo hng theo trong khng gian Hough. Mt cu trc d liu l cn thit lu tr tt c cc cell vi tham s tnh im cho mi cell. Trong phn tip theo s cp cch tng im ca mt cell v lng gia tng im s bng 1. Cu trc d liu ny gi l b tch ly, c m t chi tit hn trong phn sau. i vi mi im bin i Hough s x l tng tt c cc cell c lin quan n n. Qu trnh gia tng ny thng c gi l qu trnh b phiu, tc l, mi im b phiu cho tt c cc b tham s (, , ) xc nh mt mt phng m trn n c th nm trn, tc l, nu khong cch euclidian t im ang xem xt n mt phng i din bi cell nh hn mt ngng. Cc cell vi cc gi tr cao nht i din cho nhng mt phng ni bt nht, mt phng bao gm hu ht cc im ca m my im.

Mt khi tt c cc im bnh chn, nhng mt phng chin thng c la chn. Do s ri rc ca khng gian Hough v nhiu trong cc d liu u vo th nn tm kim khng ch mt cell vi s im ti a m cn tm tng ti a

trong mt khu vc nh ca b tch ly. Kiryati s dng cc tiu chun thc hnh pht hin im nh. Trong th tc ca s trt, mt ca s 3 chiu nh xc nh c thit k ph ph cc nh y . Mt phng c u th nht tng ng vi im trung tm ca mt khi lp phng trong khng gian Hough vi tng cc gi tr tch ly l ln nht. Cc bc ca th tc c nu trong thut ton 1.

Gm hai giai on

G1: Tt c cc im Pi thuc tp im P c chuyn sang khng gian Hough. Gm cc dng 1 n 7 trong gii thut

SHAPE \* MERGEFORMAT

G2: Tm cc nh cao nht trong b tch ly (dng 8 trong gii thut)

Do thi gian tnh ton cao ca bin i Hough tiu chun l kh p dng thc t, c bit l cho cc ng dng thi gian thc. Do nhiu bin th c t ra. Illingworth v Kittler a ra mt cuc kho st v s pht trin sm v ng dng. Klviinen thc hin so snh phin bn sa i ca bin i Hough nhm lm cho cc thut ton thc t hn. Mt s trong nhng th tc c m t trong cc phn di y. Phn cui cung cp mt nh gi ca cc phng php ny vi mc ch tm ra s thay i ti u cho nhim v pht hin s lng mt phng khng bit trc trong mt m my im 3D.

1.2.2 Phng php bin i Hough theo xc sut (Probability)

Bin i Hough tiu chun c thc hin trong hai giai on. u tin, tt c cc im pi t tp im P c chuyn sang khng gian Hough, tc l, cc cell trong b tch ly c tng ln. iu ny cn O (| P | N N) php ton khi tnh ton mt duy nht tng ng vi mt phng m trn im pi c cho trc v , vi N l s lng cell theo hng , N theo hng v N theo hng , tng ng. Th hai, trong giai on tm kim cc nh cao nht trong b tch ly c pht hin trong O (N N N) php ton. V kch thc ca m my im | P | thng ln hn nhiu so vi s N N N ca cc cell trong mng accumulator, ci tin ln lin quan n chi ph tnh ton c thc hin bng cch gim s lng cc im hn l bng cch iu chnh qu trnh ri rc trong khng gian Hough. Kiryati xut mt phng php xc sut la chn mt tp hp con t tp im ban u. S thch nghi ca SHT tr thnh bin i Hough xc sut (PHT) c trnh by trong thut ton 2. SHAPE \* MERGEFORMAT

Cc im m (m