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Fig. 6.9
Cable Scene. It is evident that the reconstructed cable is located above the table plane
(z
=
0 ) . The world coordinate system has been defined by estimating the pose of the chequerboard
Fig. 6.10 Three-dimensional reconstruction of a glue line on the non-planar surface of a car body
part ( left ), resulting three-dimensional ziplock ribbon snake ( right )
Although the object is not flexible, a pose estimation method for rigid objects cannot
be applied due to the lack of an accurate geometry model. Hence, the multiocular
ziplock ribbon snake algorithm is an adequate approach to reconstruct the three-
dimensional shape of the glue line. Again, the images were acquired with the Digi-
clops system, and the object was situated at a distance of about 0 . 7 m to the camera.
The accuracy of the reconstruction result compared to ground truth obtained with a
calliper gauge amounts to 1 mm, corresponding to 1 . 5pixels.
A scenario that goes beyond mere quality inspection is illustrated in Fig. 6.11
in a laboratory environment. A bar code is desired to be read by a monocular
camera (camera 2 in Fig. 6.11 a) but is partially occluded by a cable. The trajec-
tory of the cable is reconstructed with the multiocular ziplock snake method (cf.
Fig. 6.11 b-c) using the Digiclops trinocular camera system (camera 1 in Fig. 6.11 a).
As soon as the three-dimensional pose estimation has been performed as indicated
in Fig. 6.11 c, the industrial robot grasps the cable and holds it aside, as shown in
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