US Patent 8553236: Optical Targets For Machine Vision .

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Illlll llllllll Ill lllll lllll lllll lllll lllll nited States PatentDorrance et al.(45)(54) OPTICAL TARGETS FOR MACHINE VISIONVEHICLE SERVICE SYSTEM(75)Inventors: Daniel R. Dorrance, Ballwin, MO (US);Nicholas J. Colarelli, III, Creve Coeur,MO (US); Timothy A. Strege, SunsetHills, MO (US); Thomas J. Golab, St.Peters, MO (US): David A. Voeller, St.Louis, MO (US); Mark S. Shylanski,University City, MO (US)(73) Assignee: Hunter Engineering Company, St.Louis, MO (US)( *)Notice:Subject to any disclaimer, the term of thispatent is extended or adjusted under 35U.S.C. 154(b) by 507 days.(21) Appl. No.: 12/873,455(22)(65)Filed:Sep.1,2010Prior Publication DataUS 2011/0051151 AlMar. 3, 2011Related U.S. Application Data(60)Provisional application No. 61/238,711, filed on Sep.1, 2009.Int. Cl.GOJB 11114(2006.01)G02B 5112(2006.01)(52) U.S. Cl.USPC . 356/620; 359/524(58) Field of Classification SearchUSPC . 359/524See application file for complete search history.(51)(56)(IO)References CitedU.S. PATENT DOCUMENTSPatent No.:US 8,553,236 B2Date of Patent:Oct. 8, 0685222007/01015952008/0186383. 356/139.09A * 7/1996 Spann et al.3/1998 JanuaryAA512000 January et al.Bl* 1112002 Rajan et al. 428/349Bl3/2004 AdolphBl512005 Dorrance et al.Bl* 212007 Guangjun et al. 73/146B22/2008 Dorrance et al.B211/2008 Stieff et al.B2 * 12/2008 Braghiroli . 356/607Al* 312005 Dorrance et al. 356/139.09Al* 5/2007 Jackson et al. . 33/293Al* 8/2008 Dorrance et al. . 348/148OTHER PUBLICATIONSBosch, "Bosch Diagnostics OES. Solutions for efficient service",Bosch product literature No. AA-DG/MKT3 1 987 749 008, 12pages, Sep. 2005, Plochingen, Germany.Beissbarth, "Beissbarth-Workshop Equipment Recommended byBMW", Beissbarth product literatme No. 1693 612 001 EN, 14pages, Mar. 2009, Muenchen, Germany.* cited by examinerPrimary Examiner Gregory J. Toatley, Jr.Assistant Examiner - Juan D Valentin, II(74) Attorney, Agent, or Firm Polster Lieder Woodmff &Lucchesi, L.C.ABSTRACT(57)An optical target for temporary application in non-determined placement on a surface of an object such as a vehiclewheel assembly within the field of view of an imaging sensorofa machine vision vehicle service system. The optical targetconsists of a flexible body which is relatively thin and generally flat, capable of conforming to the contours of a surfaceonto which it is secured in releasable marmer by a means ofadhesion. A set of visible optical elements are disposed on afront face of the target body for observation and imaging bythe imaging sensors.4,121,851 A * 10/1978 Finkenbiner . . . . 280/288.44,882,211 A * 1111989 Mcintyre et al . 428/41.65,466,502 A * 1111995 Wilkinson et al. . 428/42.117 Claims, 3 Drawing SheetsTURNPLATEcr---flELDDrVIEW'\/-11:.LrRONT CAM(RA(12)(11)FIELO Of VIEWRUNWAYRUNWAY.,., t1. -l···---REAR CAMERA(12)FIELD OF VIEW

U.S. PatentOct. 8, 2013US 8,553,236 B2Sheet 1of310 OPTICALTARGETF I G. 1TARGETMOUNTINGASSEMBLYPRIOR ART108102s'---100FIG.2

U.S. PatentOct. 8, 2013Sheet 2 of 3US 8,553,236 B2100RIMTIREFIG.3


US 8,553,236 B212OPTICAL TARGETS FOR MACHINE VISIONVEHICLE SERVICE SYSTEMterms of processing the images acquired by the imaging sensors, it introduces a new set of problems. In particular, theconstruction of the optical target structures is time consumingand expensive, as they are manufactured to precise specifications, and they require specialized mounting components forattachment to the object surfaces, such as wheel assemblies,which limit the possible placement locations within a field ofview.Accordingly, it would be advantageous to provide a lowcost optical target which may be temporarily placed in anon-determined position on a wide range of object surf;aceswithin the field of view of a machine vision vehicle servicesystem to provide a set of identifiable features or target elements within an acquired image for subsequent measurementprocessing. It would be further advantageous to provide sucha low-cost optical target with a means for attaclnnent to theobject surfaces which does not require specialized mountingstructures, and which is readily removable and is optionallyreusable or consumable.CROSS-REFERENCE TO RELATEDAPPLICATIONSThe present application is related to, and claims priorityfrom, U.S. Provisional Patent Application Ser. No. 61/238,711 filed on Sep. 1, 2009, which is herein incorporated byreference.10STATEMENT REGARDING FEDERALLYSPONSORED RESEARCHNot Applicable.15BACKGROUND OF THE INVENTIONThe present invention is related generally to machinevision vehicle service systems, and in particular, to a multielement optical target which may be temporarily positionedin a non-detem1ined placement on a surface within a field ofview of an imaging sensor associated with a machine visionvehicle service system during a vehicle service procedure, tofacilitate the acquisition of measurements associated with thesurface.Machine vision vehicle service systems typically utilizeone or more imaging sensors to acquire images of objectsdisposed within a field of view. The acquired images areprocessed by suitably configured processing systems toextract data associated with the observed objects. Theextracted data may identify the position and orientation of theobserved object within the field of view, or may providemeasurements of movement of the object.Some machine vision vehicle service systems are configured to process images of objects directly observed, i.e. thesurfaces of wheel assemblies or wheel rims, vehicle bodypanels, or suspension components. These machine visionvehicle service systems require significant image processingcapabilities, as the objects being observed are generally of anunknown configuration, which renders it difficult to obtainmeaningfol measurements without the use of complex imaging sensor configurations or advanced image processing techniques.Traditionally, most machine vision vehicle service systemsrequire the operator to dispose one or more optical targetstructures within the field of view of the imaging sensors priorto the acquisition of the images. The optical target structureshave known or predetermined features which are highly visible to the imaging sensors, such as retro-reflective geometricpatterns, and are disposed in the field of view in such a manneras to be associated with the objects being observed. Forexample, it is well known to secure rigid optical target structures, such as shown in U.S. Pat. No. 6,710,866 Bl to Adolphhaving a plurality of optical target elements onto a vehiclebody panel or onto vehicle wheel assemblies using a mounting or other attachment structure which can be removablysecured to the wheel assembly in a fixed relationship. The useof optical target structures provides the imaging sensors withhighly visible elements in the acquired images, which haveknown features for subsequent image processing. Since theoptical target structures are mounted in association with theobserved objects, position and measurement data acquiredfrom the observation of the optical targets may be related tothe observed object.While the use of optical target structures offers distinctadvantages to a machine vision vehicle service system in202530354045505560BRIEF SUMMARY OF THE INVENTIONBriefly stated, the present disclosure provides an opticaltarget for temporary application to a surface of a vehiclewheel assembly in a non-determined position within the fieldof view of an imaging sensor of a machine vision vehicleservice system. The optical target consists of a body definedby a sheet of material such as vinyL paper, or cardboard, mayoptionally include a layer of a self-adhesive material appliedto a back surface, and further includes at least one opticaltarget element disposed on the opposite (front) surface forobservation by the imaging sensor.In one embodiment of the present disclosure, the opticaltarget is composed of a flat body of a flexible vinyl materialadapted to conform to the surface of a wheel assembly. Areleasable contact adhesive is disposed on the back surface,while a set of high-contrast optical target elements are printedon a front surface in a predetermined configuration.During use with a machine vision vehicle service system,one or more optical targets of the present disclosure are positioned in non-determined placement onto the surfaces of avehicle wheel assembly to be observed, such as by the selfadhesive material, with the front face optical target elementsare generally visible to the imaging sensors of the machinevision vehicle service system. Images of the vehicle wheelassembly, and the associated optical targets are acquired bythe imaging sensors, and are processed to identity any visibleoptical target elements. Processing of the images of the identified visible optical target elements, together with the predetennined configuration of the optical target elements on theoptical targets, provide measurement data associated with thevarious optical targets present in the field of view, and whichcorresponds to measurement data associated with the surfaces of the vehicle wheel assembly onto which the opticaltargets are presently positioned. Upon completion of avehicle service procedure, the optical targets are removedfrom the object surfaces and are stored for future use, or arediscarded.The foregoing features, and advantages set forth in thepresent disclosure as well as presently preferred embodiments will become more apparent from the reading of thefollowing description in com1ection with the accompanyingdrawings.BRIEF DESCRIPTION OF THE SEVERALVIEWS OF THE DRAWINGS65In the accompanying drawings which form part of thespecification:

3US 8,553,236 B2FIG. 1 is a perspective view of a prior art optical targetmounted to a wheel assembly;FIG. 2 is a front view of an exemplary optical target of thepresent disclosure;FIG. 3 is a perspective view of a wheel assembly ontowhich three of the exemplary optical targets of FIG. 2 havebeen temporarily placed at the spoke/rim junctions; andFIG. 4 illustrates an exemplary placement of cameras forviewing optical targets of the present disclosure placed on thewheels of a vehicle disposed on a vehicle support structureduring a service procedure.Corresponding reference numerals indicate correspondingparts throughout the several figures of the drawings. It is to beunderstood that the drawings are for illustrating the conceptsset forth in the present disclosure and are not to scale.Before any embodiments of the invention are explained indetail, it is to be understood that the invention is not limited inits application to the details of construction and the arrangement of components set forth in the following description orillustrated in the drawings.101520DETAILED DESCRIPTIONThe following detailed description illustrates the inventionby way of example and not by way oflimitation. The description enables one skilled in the art to make and use the presentdisclosure, and describes several embodiments, adaptations,variations, alternatives, and uses of the present disclosure,including what is presently believed to be the best mode ofcarrying out the present disclosure.Turning to the figures in general, and to FIG. 2 in particular,an optical target of the present disclosure for temporary application to the surface S ofanobject 10, such as a vehicle wheelassembly or vehicle body panel, within the field of view of animaging sensor 12 of a machine vision vehicle service system. The optical target 100 consists of a generally planar body102 defined by a sheet or layer of flexible material having abaek surfaee 104 adapted for placement against the surface Sof the object 10, such as a paper, cardboard, or vinyl material.The material is preferably sufficiently flexible to conform tothe contours of the surface S of the vehicle wheel assembly orother object onto which the target 100 is being disposed, andis preferably sufficiently durable to withstand repeated useswithout ripping, tearing, or deforn1ing. However, it will bereadily recognized that durability of the optical targets 100 isnot required, and that the optical targets 100 may be manufactured as a consumable product intended for disposal afteronly one or more uses.As used herein, the phrase "planar body" is not intended tobe limited to a rigid structure, but rather, is intended todescribe a structure having two dimensions (length andwidth) which are significantly greater in size than the thirddimension (thickness). The front surface 106 of the planarbody 102, opposite the back surface 104, includes a set ofoptical target elements 108 having generally known featuresand relationships. The optical target elements 108 are preferably in the form of markings on the front surface 106 whichare highly contrasted against the front surface 106.For example, as seen in FIG. 2, the optical target elements108 may be in the fonn of black circles disposed on a whitesurface 106. Those of ordinary skill in the art will recognizethat the optical target elements 108 may be formed in anymanner suitable for observation by the imaging sensors 12 ofthe machine vision vehicle service system 14, and mayinclude the use of color, retro-reflective materials, or opticalpatterns.2530354045505560654The optical target 100 is intended for temporary placementagainst the surface S of an object in a non-determined location, without the use of a mounting stmcture or other externalattacl1111ent means, such as shown in FIG. 3. As used herein,the phrase "non-determined location" describes a placementlocation on the surface S of an object such as a vehicle wheelassembly which is not predetermined or known in advance,such as a required target placement position. For example, anon-detern1ined location on a vehicle wheel assembly may beon any surface between an axis of rotation of the vehiclewheel assembly and an outer rim lip of the vehicle wheelassembly.Preferably, the optical target 100 is self-adhesive, andincludes an adhesive means such as a releasable contact adhesivelayerdisposedon the back surface 104, which permits theoptical target to be smoothly applied directly on the objectsurface S. Ifthe planar body 102 is flexible, the flexible natureof the planar body 102 may be conformed to the shape of theobject surface S at the placement location. Alternatively, if theplanar body 102 is rigid, the planar body 102 will define a flatsurface secured to the object's surface S. Those of ordinaryskill in the art will recognize that a variety of means foradhesion may be employed to temporarily secure the opticaltarget 100 to the object surface S, and are not limited toapplied layers of glues or chemical compositions. Forexample, the means for adhesion may including frictionalengagement between the back surface 104 and the objectsurface S, electrostatic attraction, intermolecular attractionsuch as van der Waals forces, or water surface tension (i.e.,wetting the surface before application of the optical target100). Preferably, the means for adhesion employed with theoptical target 100 permits easy removal of the optical target100 from the object surface S, leaves little or no residue on theobject surface S, does not damage or destroy the optical target100, and permits optional re-use or re-positioning of theoptical target 100.During use with a machine vision vehicle service system,one or more optical targets 100 of the present disclosure arepositioned in non-determined placement onto the surfaces Sof an object 10 such as a vehicle wheel assembly to beobserved, with the releasable adhesive or other attachmentmeans, as seen in FIG. 3. The optical targets 100 are positioned such that the front face 106 and the optical targetelements 108 are generally visible to the imaging sensors 12of the machine vision vehicle service system. For example, asshown in FIG. 4, imaging sensors 12 may be disposed inproximity to the location of a vehicle's wheels when thevehicle is positioned on a vehicle support structure, such as alift. Preferably, the field of view of each imaging sensor,which may be fixed or adjustable, is aligned generally perpendicular to the object surface S to facilitate viewing of theoptical targets 100, however, those of ordinary skill in the artof machine vision systems will recognized that the imagingsensors 12 may be disposed in a variety of positions andconfigurations to acquire images of the optical targets 100within associated fields of view.Images of the object or wheel assembly surface S, and theassociated optical targets 100 are acquired by the imagingsensors 12, and are processed according to known imageprocessing teclmiques to identity images of optical targetelements 108 present in the associated fields of view. Processing of the images of the identified visible optical target elements 108, together with data associated with the predetermined configuration of the optical target elements 108 on theoptical targets 100, provides measurement data associatedwith the position and orientation of the various optical targets100 present in the field of view of the imaging sensors 12, and

US 8,553,236 B25which corresponds to measurement data associated with thesurfaces S of the objects 10 such as vehicle wheel assemblies,onto which the optical targets 100 are presently positioned.Image processing algorithms and techniques for detem1iningspatial position and orientation of the optical targets andobject surfaces are well known to those of ordinary skill in thefield of machine vision vehicle service systems. For example,suitable image processing algorithms and techniques foracquiring three-dimensional information from objects or targets identified in the field of view of an imaging sensor 12 canbe found in U.S. Pat. No. 7,444,752 B2 to Stieff et al., in U.S.Pat. No. 7,336,350 to Dorrance et al., and in U.S. Pat. No.6,894,771 Bl to Dorrance et al., each of which is hereinincorporated by reference. Additional teclmiques for processing acquired images of optical targets can be found in U.S.Pat. No. 6,064,750 to January et al. and in U.S. Pat. No.5,724,128 to January, both of which are incorporated by reference.Upon completion of a vehicle service procedure, the optical targets 100 are removed from the object surfaces and areeither stored for future use, or are discarded and replaced ifthey are damaged, dirty, or lack remaining suitable adhesivecharacteristics.TI1ose of ordinary skill in the art will recognize that theparticular configuration and shape of the optical target 100, aswell as the arrangement of the optical target elements 108 onthe front face 106 is not limited to the configuration shown inthe Figures, and that any suitable shape and arrangementhaving identifiable features required for measurement of theintended characteristics of an object's surface may be utilized. For example, the number and shape of the optical targetelements 108 may be varied from circles to triangles, andfrom an arcuate pattern to a linear pattern without departingfrom the scope of the present disclosure.It will further be recognized by those of ordinary skill in theart that the optical targets 100 need not be manufactured in acontrolled high-precision fashion, but rather, may be printedon-demand onto a suitable body material 102 such as pre-cutself-adhesive stickers or labels supported on a sheet of releasepaper, using commonly available printing systems such as alaser printer, themial printer, or an ink-jet printer, controlledby suitab

Beissbarth, "Beissbarth-Workshop Equipment Recommended by BMW", Beissbarth product literatme No. 1693 612 001 EN, 14 pages, Mar. 2009, Muenchen, Germany. * cited by examiner Primary Examiner Gregory J. Toatley, Jr. Assistant Examiner - Juan D Valentin, II (74) Attorney, Agent, or Firm Polster Lieder Woodmff & Lucchesi, L.C. (57) ABSTRACT

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