Method and system for geometry measurements

Abstract

Method and system for determination of relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders or spheres, or combined objects like robot arms or other industrial production equipment, based on the use of one or more cameras based on electro-optical sensors, in combination with permanently mounted light sources, projected light spots,illuminated reflectors, or probing tools having light sources or reflectors attached thereto. The camera ( 1 ) is arranged to measure the projection of light spots on the cameras sensor ( 4 ) in a number of camera locations, and measurements are made such that each light source or light reflection ( 18; 14; 15; 16 ) is observed from two or more camera locations ( 1; 8 ), by the observations being registered as image coordinates relates to a camera fixed coordinate system. Based on the observed images of the light sources ( 14; 15; 16 ) or reflecting points of the measurement tool, the corresponding image coordinates of the touch point of the measurement tool are calculated in the camera fixed coordinate system. Among the measurement points there is a minimum of two points at a known mutual separation distance to be used for determination of correct length scale. The positions of the individual points relative to an arbitrary coordinate system are calculated by bundle adjustment, and where the computational method also comprises a mathematical modelling of the optical properties of the cameras to compensate for distortion errors in the camera lens, and where the mathematical descriptions of geometrical objects are based on analysis of a number of points on the object.

1 . Method for determination of relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders or spheres, or combined objects like robot arms or other industrial production equipment, based on the use of one or more cameras based on electro optical sensors, in combination with permanently mounted light sources, projected light spots, illuminated reflectors, or probing tools having light sources or reflectors attached thereto, characterized in 
 that said camera is mounted for measurement of the projection of light spots on the camera sensor in a number of camera locations,    that measurements are made such that each light source or light reflection is observed from two or more camera locations, and that the observations are registered as image coordinates related to a camera fixed coordinate system,    that calculation of the image coordinates of the image of the touch point of the measurement tool in the camera fixed coordinate system, is based on the corresponding observed images of the light sources or reflecting points of the measurement tool,    that there among the relevant measurement points are at least two points in a known mutual separation distance to be used for determination of a correct length scale,    that the positions of the individual points relative to an arbitrary spatial coordinate system are calculated by a bundle adjustment, where the computational method also comprises a mathematical modelling of the optical properties of the cameras to compensate for distortion errors in the camera lens, and    that the mathematical description of geometrical objects are based on analysis of a number of points on the object.    
     
     
         2 . Method for determination of position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in  claim 1 , relative to a defined coordinate system, characterized in 
 that a minimum of three points have one or more of its coordinate values known relative to said coordinate system, such that a minimum of six coordinate values are known and distributed such that three values are defined relative to one coordinate axis, two relative to a second axis, and one relative to a third axis, and    that these known coordinate values are used to calculate the position and orientation of all other points and geometrical objects relative to this coordinate system.    
     
     
         3 . Method for determination of the relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in  claim 1  or  2 , characterized in 
 that the individual light spots are registered simultaneously by two or more cameras, and hence to allow the light spots to move during measurements and/or to achieve faster data acquisition.  
 
     
     
         4 . Method for determination of the relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in anyone of claims  1 - 3 , characterized in 
 that a number of measurement points being active light sources, reflecting points or points to be measured by the use of a measurement tool having light sources or reflecting points attached to it, are arranged as help reference points to increase the number of points and hence to increase the accuracy in the calculation of position and orientation of all points.    
     
     
         5 . Method for determination of the relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in anyone of claims  1 - 3 , characterized in 
 that a reference structure is arranged inside the measurement volume and that to said reference structure being attached a number of active light sources, reflecting points or points to be measured by the use of a measurement tool having light sources or reflecting points attached to it, and with known coordinates in a well defined coordinate system, and    that measurement and calculation of coordinates for additional points is based on measurement of a selection of points on said reference structure together with these additional points.    
     
     
         6 . Method for determination of the relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in anyone of claims  1 - 3 , characterized in 
 that the measurement volume is surrounded by a reference structure having attached thereto a number of active light sources, reflecting points or points to be measured by the use of a measurement tool having light sources or reflecting points attached to it. and with known coordinates in a well defined coordinate system, and    that measurement and calculation of coordinates for points on an actual object is based on the object being position within said reference structure, and measurement of a selection of points on said reference structure together with these additional points.    
     
     
         7 . System for determination of relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders or spheres, or combined objects like robot arms or other industrial production equipment, based on the used of one or more cameras based on electro optical sensors, in combination with permanently mounted light sources, projected light spots, illuminated reflectors, or probing tools having light sources or reflectors attached to it, characterized in 
 means for flexible data acquisition that allows said camera to be mounted for measurement of the projection of light spots on the camera sensor in a number of camera locations, and where the data acquisition is made such that each light source or light reflection is observed from two or more camera locations, and that the observations are registered as image coordinates related to a camera fixed coordinate system,    means for calculation of the image coordinates of the image of the touch point of the measurement tool in the camera fixed coordinate system, based on the corresponding observed images of the light sources or reflecting points of the measurement tool,    means for giving scale information to the system, said means being a bar to which there is attached a minimum of two light sources, reflecting points or points to be measured by the use of said measurement tools, at known mutual separation distance,    means for calculation of the position of the individual points relative to an arbitrary spatial coordinate system by bundle adjustment, and where the computational method also comprises the optical properties of the cameras to compensate for distortion errors in the camera lens,    means for mathematical description of geometrical objects based on analysis of a number of points on the object.    
     
     
         8 . System for determination of position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in  claim 7 , relative to a defined coordinate system, characterized in 
 means based on a minimum of three points having one or more of its coordinate values known relative to said coordinate system, such that a minimum of six coordinate values are known and distributed such that three values are defined relative to one coordinate axis, two relative to a second axis, and one relative to a third axis, and for using these known coordinate values to calculate the position and orientation of all other points and geometrical objects relative to this coordinate system.    
     
     
         9 . System for determination of the relative position and/or orientation of a number of points or geometrical objects like planes, lines, holes, cylinders, spheres etc. as claimed in  claim 7  or  8 , characterized in 
 means for synchronizing the activation of the individual light spots and the registering by two or more cameras, to allow the light spots to move during measurements and/or to achieve faster data acquisition.