The concept of virtual landmarks in 3D multi-view fringe projection

For a 360-deg 3D measurement of an object the optical 3D sensor scan the object from different positions and the resulting single patches have to transform into a common global coordinate system so that these point clouds are patched together to generate the final complete 3D data set. Here we summarize and give some system realizations for the method, which we called "method of virtual landmarks" /1, 2/ realizing this local-global coordinate transformation without accurate mechanical sensor handling, sensor tracking, markers fixed on the object or point-cloud based registration techniques. For this the calculation of the co-ordinates, orientation of the sensor and local-global coordinate transformation is done by bundle adjustment methods, whereby the pixel of the so called connecting camera form 'virtual landmarks' for the registration of the single views in order to obtain a complete all around image. The flexibility makes the method useful for a wide range of system realizations which will be shown in the paper, like robot guided, handheld /3/ and tripod based systems for the flexible measurement of complex and/or large objects.