非线性滤波在射线图像降噪增强中的应用

,(,030051):,,,,:;;;;:TG115.28:A:100026656(2002)0720281205APPLICATIONOFNONLINEARFILTERINGTOREDUCINGNOISEANDENHANCINGRADIOGRAPHICIMAGEWANGMing2quan,HANYan(NDTCenter,NorthChinaInstituteofTechnology,Taiyuan030051,China)Abstract:Real2timedigitalradiographyisadevelopmenttendencyforradiographicinspectionanddiagnosis.En2hancementofimageisthekeytoimproveresolutionandsensitivityofradiographicinspection.Thealgorithmandcharac2terofrank2orderfilterwhichisoneofthenonlinearonesarediscussedemphatically.Allmethodshavebeenusedtopro2cessradiographicimageandtheresultshaveillustratedthatlinearfiltercanreducenoisebutcorruptedge,andrank2orderfiltercanreducenoiseandpreservethedetailatthesametime,andiseffectiveonimprovingimagequality.Keywords:Radiographictesting;Imageprocessing;Linearfilter;Nonlinearfilter;Rank2orderfilter,,,,,,[1]11,:20012082231X1,,X18224720027NDTVol.24No.7July2002©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.2,,,,(),,2,f0(x,y),MTF0,g(x,y),MTF1,,g1(x,y)2MTF1,,,,,2,g(x,y),h(x,y),g1(x,y),g1(x,y)=g(x,y)3h(x,y)(1)3G1(x,y)=G(x,y)H(x,y)(2),H(x,y)MTF1W(),1h(n)=[,0,1,1,1W,0,](3)h(n)N(NW)H(k)=N-1n=0h(n)e-j2Nnk=W-1n=0e-j2Nnk==1-e-j2NWk1-e-j2Nk=e-jkN(W-1)sinNkWsinNk(4)k=0,1,,N-1(4),,H(k),N,N/2,N,33,55,77,,,,N,,,,W1,1(3),g1(n)=u(n-N0)-u(n-N0-W1)(5)3N|G(k)|=sinNkW1sinNk(6)sinNkW1=0k=NW1(7)B0=1W1(8)(7)(8),,,,,,,,,MTF282:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.[2]3,,,(),,,,:3.1[3],f(x,y),(2k+1)(2l+1),g(x,y)=Medxki=-kMedylj=-l[f(x+i,y+j)](9)MedxMedy,,;,,,,,,3.2,,,,,,,,,,,,kJYkYk=XN+1-JkkMkXN+1+JkkMk(10)2N+1;Xk-N,,Xk,,Xk+N;X(i)k,i;kMk,J1JNJ=N,;J=0,,,,,J3.322J,,,,,J,,,,,,,,,,22(LUM)[4]LUM,,LUM,(lower)(upper)(middle)LUMLUMLUM,,382:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.,,,,,,,;LUM,,,LUM,N,^x,,(2m+1)(2m+1)=Nx(1)x(2)x(N)(11)^y3.3.1LUMLUM,^y=Med{x(k),^x,x(N-k+1)}(12),Med,1k(N+1)/2,^xx(k),LUMx(k),^xx(N-k+1),x(N-k+1),^xkk=(N+1)/2,LUM;k,;k=1,^x=^y,3.3.2LUM,,,LUMLUM,x(l)x(N-l+1),l1l(N+1)/2,tl=x(l)+x(N-l+1)2(13)^y=x(l)x(l)^xtlx(N-l+1)tl^xx(N-l+1)^x(14),x(l)^xx(N-l+1),^xx(l)x(N-l+1),^xl,l=(N+1)/2,LUM;l=1,^x,x(l)x(N-l+1)3.3.3LUMLUM,^y=x(k)^xx(k)x(l)x(l)^xtlx(N-l+1)tl^xx(N-l+1)x(N-k+1)x(N-k+1)^x^x(15),1kl(N+1)/2kl,LUM,,4,4LUM4al=(N+1)/2,k,LUMk,,k=l=(N+1)/24bk=1l,LUMl,x(l)x(N-l+1),4c1kl(N+1)/2,,,LUM;,LUM,,41(X60keV,0.3mA,0.5mm)5a,,555b,;5ce,;482:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.55f,;5giLUM,,,;,,;;LUM,kl,,k=3,l=3,,LUM5,,,,(),:[1],.[M].:,1993.1-50.[2].X[D].:,1998.[3]ArecGR,FosterRE.Detailpreservingranked2orderbasedfiltersforimageprocessing[J].IEEETransAc2costSpeechSignalProcessing,1987,37(7):83-98.[4]HardieRC,BonceletCG.LUMfilters:aclassrankor2derbasedfiltersforsmoothingandsharpening[J].IEEETransSignalProcessing,1993,41(3):1061-1076.2002GB9445,,20029(),()::80:710032:[phone],3291311,2488508:13909212711:[e-mail]()582:©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.