计算机视觉课件_LC21_cvln_intro.ppt

3DComputerVision Dr ShengyongChenEmail sy ieee org 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 spatialrelationshipsThe where pathway 11 12 RecommendedbooksShapiro L Stockman G 2001 ComputerVision PrenticeHall RichardHartleyandAndrewZisserman MultipleViewGeometryinComputerVision CambridgeUniversityPress 2000 ForsythandPonce ComputerVision AModernApproach PrenticeHall 2003 Further 13 Otherresourceson lineAnnotatedComputerVisionBibliography http iris usc edu Vision Notes bibliography contents htmlTheComputerVisionHomepage CarnegieMellonUniversity http www 2 cs cmu edu cil vision htmlIntelOpenSourceComputerVisionLibrary Further 14 Introduction TheeyesMethodsof3DVision 15 Today sclass CameraandWorldGeometry Howtallisthiswoman Whichballiscloser Howhighisthecamera Whatisthecamerarotation Whatisthefocallengthofthecamera 16 Figures StephenE 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 SurfaceshapesarethendeducedfromthedistortionsofthepatternsthatareproducedonObject sSurface 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 Pass