have been performed. The first set-up is shown in Fig-
ure 5 and in the second set-up the camera is mounted
as close as possible to the profile sensor. Thereby, ei-
ther two, five or ten object positions scattered inside
of the reference areas were used. However, an in-
creased number of reference points has no significant
influence on the results. Thus, a number of N = 4 ref-
erence points is sufficient. The resulting mean values
and the standard deviation values for each parameter
are shown in Table 1 and 2.
Table 1: Parameter estimation for first experimental
set-up.
t (mm) σ (mm) r (deg) σ (deg) Error (pixel) σ (pixel)
72.3995 0.8716 34.4061 0.1101
80.1886 0.3726 -22.9854 0.2741 0.9349 0.1891
20.5744 0.4808 -3.4034 0.1325
Table 2: Parameter estimation for second experimen-
tal set-up.
t (mm) σ (mm) r (deg) σ (deg) Error (pixel) σ (pixel)
1.9726 0.0445 -9.2074 0.0310
-32.7163 0.1503 -5.9926 0.0370 0.8696 0.0721
-18.5722 0.3498 -89.2548 0.0621
The realized approach achieves stable solutions
and consequently a good repeatability. The validation
shows low standard deviation values for the transfor-
mations (σ < 1mm, σ < 0.3
◦
). A good absolute accu-
racy is also achieved with average pixel errors below
the resolution of the camera (1 pixel). This error oc-
curs partially by rounding errors that can hardly be
avoided.
The calibrated sensors are used for workpiece
scanning with two robot arms (cf. Section 2.1). Fig-
ure 9 shows a partial reconstruction of some Lego
bricks held up by a gripper. Due to the contained color
information, it can be clearly distinguished between
the individual bricks and the gripper.
5 CONCLUSIONS
In this paper, a color extension for a 2D laser profile
sensor by getting the color information from a cam-
era is presented. For this purpose, a sensor fusion be-
tween the two sensors has been realized. Therefore,
a flexible calibration routine has been created. Indefi-
nite planar calibration objects are usable with this ap-
proach regardless of their color. The accuracy of the
approach is confirmed through experiments. A pixel
error close to the resolution of the camera has been
achieved.
(a) Scene (b) Point cloud
Figure 9: Example for a colored reconstruction.
So far, the coloring needs approximately 4 ms per
profile point. Future work will be focused on the time
optimization of the process. In addition, an improve-
ment of the reference point distribution, by splitting
the profile sensor measurement range in sections and
a partial restriction on one reference point per section,
is prospected.
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