EasyGauge user manual.docx
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- 上传时间:2023-07-26
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EasyGauge user manual.docx
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EasyGaugeusermanual
WhatisEasyGauge?
∙ Sub-pixelpointlocationandedgefittingforgaugingapplications
∙Highlyaccurateandrobust
∙Position,orientation,size,curvature,distances…
∙Advancedcalibration
∙Multiplegaugemodels
∙Graphicalmodeledition
∙andmuchmore...
EasyGaugeisasecond-generationmeasurementanddimensioncontrollibraryforuseingaugingapplications.Byrelyingonprovensub-pixeledgedetectionandleastsquaresfittingalgorithms,itallowsdeterminingtheposition,orientation,curvature,size…ofmanufacturedpartswithanexcellentaccuracy.Robustnessisensuredbypowerfuledge-pointselectionmechanismsthatareintuitiveandeasytotune,allowingmeasurementinclutteredimages.Inadditiontothesestate-of-the-artfeatures,EasyGaugealsosupportsadjustmentofparallelsides,thusprovidingmeansofmeasuringthicknessofflatorbentobjects,aswellaspreciselocationofcorners.
EasyGaugehasadvancedbuilt-incalibrationcapabilitiesabletotransparentlyconvertpixelmeasurementstophysicalunitsandrelievestheuseroftheneedtoconvertcoordinates.Non-squarepixelsandrotatedcoordinateaxisaresupported.EasyGaugealsoprovidesmeanstodetermineandcorrectperspectiveandopticaldistortion,withnoperformanceloss.
Lastbutnotleast,EasyGaugesupportsgroupingofthemeasurementgaugesandletsthesegroupstrackthemeasureditemsintheimage.Thesecanfreelytranslateand/orrotatewhiletheprobesarerepositionedaccordingly.Derivedmeasurementssuchasdistancesbetweenfeaturepointscanthenbecomputed.
TheEasyGaugelibrarysupportsthefollowingoperations:
∙PointLocation:
findsthepositionofalltransitionpointsalongalinesegmentprobethatcrossesoneorseveralobjectsedges,andallowsselectingthemostrelevantones.Crosswiseandlengthwisefilteringcanbeactivatedfornoisereduction;
Pointlocation-Contrast-basedselection
∙EdgeFitting:
adjustsasimplepredefinedgeometricmodelovertheedgesofanobject.Thesyntheticmodelsthatcanbefitarethelinesegment,thecircle(orarcthereof),therectangleandthewedge(disk,ring,sectororcurvilinearquadrilateral);
Lineandrectanglefitting
Circlefitting(circleandarc)
Wedgefitting(sector,ringandringsector)
∙Field-of-viewcalibration:
establishestherelationshipbetweenpointcoordinatesintherealworldandpixelsintheimage.ThecalibrationtransformishandledbyaspecificdevicenamedEWorldShape(C++)orEWorldShape(ActiveX),whichprovidesmeanstocomputetheappropriatecalibrationcoefficients(RefertosectionEWorldShapeformoreinformation).Thetransformisthenimplicitlyappliedtoallmeasurementgaugestiedtoit.
Field-of-viewcalibration
Gaugegrouping:
themeasurementgaugescanbetiedtogethersothattheirrelativeplacementremainsfixed,andtheycanbemoved(translatedandrotated)asawhole.Thisway,theplacementofthegaugescaneasilyfollowthemovementoftheinspecteditems.Groupinggaugesisachievedbyattachingthemtoacommoncoordinateframeortoanothergauge,allowingtoautomaticallytrackreferenceedges.
Gaugegroupingforobjecttracking
Modeledition:
EasyGaugeprovidesmeanstographicallyinteractwiththegaugestoplaceandsizethem,combinethemasahierarchyofgroupeditems,andstore/retrievethemandallworkingparametersto/frommodelfiles.
Together,thesebasicoperationsvirtuallyallowobtaininganygeometricmeasurementonapart.Thecalibrationtransformallowsdescribingtheinspecteditemsindependentlyoftheviewingconditionssuchasobservationdistanceanddirection,lensfocallength,opticalaberrations…Thegaugegroupingmechanismallowstocompletelydescribethegaugingtaskinasinglemodelfilereadyforuse.
EasyGaugewasdesignedinsuchawaythatthegaugingmodelcanbebuiltseparatelybymeansofagraphicaleditor,andthen"played"inthefinalapplication.Programminganinspectionapplicationissimpleandstraightforward.
Simplegauging
EventoughEasyGaugeprovidesadvancedandsophisticatedmechanismsforaccurateandcombinedmeasurements,thebasicuseisstraightforward:
accordingtothemeasurementtoperform,createthecorrespondinggaugeobject,andsettheparameterswhosedefaultvaluesarenotappropriate.TheninvoketheMeasure(C++)orMeasure(ActiveX)methodandreadtheresultingpositionparameters.
Calibratedgauging
Uncalibratedgaugingiseasytoimplementbutithasseveralmajordrawbacks:
first,measurementsareperformedina"useless"unit(thepixel),whilethepartstobeinspectednormallyhaveactualsizesexpressedinmillimeters,mils,microns,yardsandthelike;second,thecorrespondingmeasurementmodelsarenotportableinthesensethatallgaugepositionsandsizeshavetobereworkediftheviewingconditionschange;third,iftheimageformationprocessinduceserrorssuchasopticaldistortionorperspective,theresultingmeasurementwillbebiased.
Pleaserefertothecalibrationsectiontolearnhowtomasterfield-of-viewcalibration.
Onceacalibratorobjectisavailableanditscalibrationparametershavebeenadjusted,itsufficestoattachagaugetoitandallmeasurementswillimmediatelybeperformedinthecalibratedunits,withdistortion,ifany,implicitlycompensated!
Complexgauging
Insimplecases,asinglemeasurementgaugecansuffice.Forinstance,checkingthediameterofaholerequiresasinglecirclegauge.Anyway,inothersituations,morethanonemeasurementsitehastobeconsidered(severalholes,overallsizeandorthogonalityofsidestobecheckedtoo…).Placingallofthemontheinspectedscene,adjustingalltheirworkingparameterscanbecomeatedioustask.
EasyGaugeaddressesthisissuebyallowingtosaveacompletemodel,includingthecalibrationmodesandcoefficients,andthevariousgaugesattachedtoit,inasinglefile.
Inaddition,severalgaugescanbemadeintegralwitheachotherbyattachingthemtoanotheritem,withthefollowingconsequences:
∙attachingthegaugestoanEFrameShapeobjectfastensthemtogethersothatmovingtheframe(translationand/orrotation)willcauseallgaugestomoveaccordingly.Inthiscase,itisthetaskoftheapplicationprogramtoadjusttheframepositiontotracktheinspectedpart;
∙attachingthegaugestoanothergaugewillmakethemmoveaccordingtothemeasuredpositionofthesupportinggauge.Byexample,ifgaugesareattachedtoacommonrectanglegauge,andiftherectanglegaugeisdetectingtheoutlineofaparttoinspect,allgaugeswillautomaticallytrackthepartwhentherectangleoutlineisfitted.
Pointlocation
Whenonetraversesalinearprofileextractedfromanimage,alongalinesegment,anedgeappearsasatransitionfromadarkzonetoalightzone(orviceversa).Whenplottingthepixelvaluesalongthegauge,thistransitionappearsasaS-shapedcurve.Thefirstderivativeofthiscurveexhibitsapeakaroundthetransitionpoint.Thebetterthecontrast,thesharperthetransitionandthehigherthepeakare.
Pointlocationprinciple
S-shapedcurveanditsderivative
EasyGaugeextractsthepixelvaluesalongaprofile(redcurve)andthenusespeakanalysistodeterminethetransitionlocation.Apeakistheareacomprisedbetweenthederivativecurveandahorizontaluser-definedthresholdlevel.Allthepixelvaluesinthepeakareaareusedtocomputethetransitionlocation.ThisishowEasyGaugeachievessub-pixelaccuracy.
Note.Sub-pixelaccuracymayonlybereachedifthetransitionissurroundedbyalmostuniformregions.Theseregionshavetobe2pixelswideatleast.Endofnote.
Inthecaseofatransitionfromblacktowhite,theprofilecurveisincreasingandthepeaktakespositivevalues.Otherwise,thecurvedecreasesandthepeakextendsnegatively.
Peakselection
Choosinganappropriatethresholdlevelisveryimportant.Whenthethresholdvalueistoohigh,significantpeakscanbemissedandtoofewpixelvaluesareusedtoachieveagoodprecision.Ontheotherhand,settingtoolowavaluewillmakefalsepeaksappearbecauseofnoise.Toresolvethisdilemma,EasyGaugeprovidesapeakselectionmechanismthatcanrejectlowcontrastorfalseedges:
thestrengthofatransitioncanbemeasuredbythepeakamplitude(differenceinordinatebetweenthethresholdandthetopofthepeak)andthepeakarea(surfacecomprisedbetweenthethresholdlevelandthecurve).
Anytimeanedgeismeasured,thepeakamplitudeandareaaredetermined.IfeithervaluefallsbelowtheMinAmplitudeorMinArea(C++)orMinAmplitudeorMinArea(ActiveX)thepeakissimplydisregardedandnopointisassumedatthatlocation.
Thresholdlevelselection
Peakamplitudeandarea
Quiteoften,severaledgepointsarepresent.Insomeapplications,allofthemmustbeconsidered.EasyGaugeallowsmeasuringallpointsinasinglegoandretrieveallresultsafterwards.Thisisthemultipletransitionmode.
Multipleversussingletransition
Alternatively,EasyGaugeallowsselectingthemostrelevanttransition.Fourselectionrulesareavailableforpeakselection:
itcanbethehighestone,theonewiththelargestarea,theoneclosesttothegaugecenterortheNthoneencounteredstartingfromonetipofthegauge.
Bestareaandbestamplitudechoices
Closestand3rdfrombeginchoices
Peakselectioncanalsoberefinedbychoosingthetransitionpolarity:
raisingorfallingedge(i.e.positiveornegativepeak),orindifferent.
Blacktowhite,whitetoblackorindifferentpolarities
Toreducetheeffectofnoise,alocalpre-filteringoftheimagevaluesispossible.Transverse(lengthwise)filteringisachievedbyaveragingseveralparallellineswhensamplingthei
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