计算机视觉_LC21_cvln_introppt课件

3DComputerVision,Dr.ShengyongChenEmail:,2,Whyvision?,Vision=geometry+measurements+interpretation,3,Content,IntroductionStereoVisionStructuredlightvisionsystemActivevisionforrobotsLaboratory,4,Introduction,TheeyesMethodsof3Dvision,5,TheEyes,6,TheEyes,7,ProjectionfromtheRetina,8,TheOpticChiasm,9,Retinotopicorganization,Thevisualfieldmapsontovisualcortexinasystematicway.MoreofV1isdevotedtoprocessingthecentralvisualfieldthantotheperiphery.,10,MappingofVisualAreas,Thismapshowsaflattenedcortexwiththeknownvisualareasmappedontoit.,TheDorsalStream:IncludesareasMT,MST,VIP,7a,etc.Processesmotion,stereo,spatialrelationshipsThewherepathway.,11,12,RecommendedbooksShapiro,L.&Stockman,G.(2001).ComputerVision.PrenticeHall.RichardHartleyandAndrewZisserman,MultipleViewGeometryinComputerVision,CambridgeUniversityPress,2000.ForsythandPonce.ComputerVision:AModernApproach,PrenticeHall,2003.,Further,13,Otherresourceson-lineAnnotatedComputerVisionBibliography:/Vision-Notes/bibliography/contents.htmlTheComputerVisionHomepage(CarnegieMellonUniversity):/cil/vision.htmlIntelOpenSourceComputerVisionLibrary:,Further,14,Introduction,TheeyesMethodsof3DVision,.,15,Todaysclass:CameraandWorldGeometry,Howtallisthiswoman?,Whichballiscloser?,Howhighisthecamera?,Whatisthecamerarotation?,Whatisthefocallengthofthecamera?,.,16,FiguresStephenE.Palmer,2002,DimensionalityReductionMachine(3Dto2D),3Dworld,2Dimage,.,17,Projectioncanbetricky,Slidesource:Seitz,.,18,Projectioncanbetricky,Slidesource:Seitz,.,19,ProjectiveGeometry,Whatislost?Length,Whichiscloser?,Whoistaller?,.,20,Lengthisnotpreserved,FigurebyDavidForsyth,B,C,A,.,21,ProjectiveGeometry,Whatislost?LengthAngles,Perpendicular?,Parallel?,.,22,ProjectiveGeometry,Whatispreserved?Straightlinesarestillstraight,.,23,Vanishingpointsandlines,Parallellinesintheworldintersectintheimageata“vanishingpoint”,.,24,Vanishingpointsandlines,o,VanishingPoint,o,VanishingPoint,VanishingLine,.,25,Vanishingpointsandlines,SlidefromEfros,PhotofromCriminisi,.,26,Vanishingpointsandlines,PhotofromonlineTatecollection,.,27,Noteonestimatingvanishingpoints,28,LaserRangingSystems,Laserrangingworksontheprinciplethatthesurfaceoftheobjectreflectslaserlightbacktowardsareceiverwhichthenmeasuresthetime(orphasedifference)betweentransmissionandreceptioninordertocalculatethedepth.,29,LaserRangingSystems,Mostlaserrangefinders:Workatlongdistances(greaterthan15m)Consequentlytheirdepthresolutionisinadequatefordetailedvisiontasks.Shorterrangesystemsexistbutstillhaveaninadequatedepthresolution(1cmatbest)formostpracticalindustrialvisionpurposes.,30,StructuredLightMethods,Projectpatternsoflight(grids,stripes,ellipticalpatternsetc.)ontoanobject.SurfaceshapesarethendeducedfromthedistortionsofthepatternsthatareproducedonObjectsSurface.Knowingrelevantcameraandprojectorgeometry,depthcanbeinferredbytriangulation.Manymethodshavebeendevelopedusingthisapproach.Majoradvantage-simpletouse.Lowspatialresolution-patternsbecomesparserwithdistance.Somecloserange(4cm)sensorsexistwithgooddepthresolution(around0.05mm)buthaveverynarrowfieldofviewandcloserangeofoperation.,31,MoireFringeMethods,Amoireprojectionsystem,32,MoireFringeMethods,Moirefringepatterns,33,ShapefromShadingMethods,Toemployphotometricstereotechniquestoproducedepthmeasurements.Usingasinglecamera,twoormoreimagesaretakenofanobjectinafixedpositionbutunderdifferentlightingconditions.Bystudyingthechangesinbrightnessoverasurfaceandemployingconstraintsintheorientationofsurfaces,certaindepthinformationmaybecalculated.,34,Pa