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6 EXPERIMENTAL SETUP AND RESULTS 
We use a flexible experimental setup comprising the two range sensors and a Mitsubishi five-degrees-of freedom 
robot (Movemaster RV-M1). Each of the two range sensors consists of a structured light projector and a CCD- 
camera. They are mounted obliquely above the scene to be analyzed and thus, they can "see" vertical and 
overhanging surfaces (see Figure 1). The image processing is done on a SUN workstation which also controls 
the generation of the light stripe patterns, the image acquisition and the robot movements. Up to now we only 
use a two finger robot-hand to grasp or push the objects in the scene. The fingers are moved against each other 
along the same line and have no additional joints (parallel gripper). Several scenes, containing up to 10 objects 
have been analyzed successfully (removing one object after the other), until the scene was empty. An example 
scene containing 7 objects is shown in Figure 4. The actual grasping by the robot has not been implemented 
yet but no particular difficulties are foreseen. A variant of this work, which uses a different data representation, 
has already successfully implemented the grasping step (see [Trobina and Leonardis 1995]). 
Figure 4: Example scene: 
(a) shows the scene as seen by the left camera. (b)-(g) display the 
merged and segmented range images for each step of the clearing 
process. À 1:1 model of the robot hand is projected into the scenes 
to show the grasping positions. The disposal area is on the lower 
right side, so the objects are removed starting from the right. First 
the tape roller is taken away (b) and then the box (c). Only in (d) 
the “Tipp-ex” bottle is removed. It is not taken in (c) because it was 
not possible to grasp it without collision. In (e) the “Läkerol”-box 
is selected because it lies slightly closer to the disposal area than the 
other two objects. Then the paint can is removed (it has the same 
distance as the rubber gum, but is higher) and finally the rubber 
gum is taken away (g). (Besides, the small ball has removed itself!). 
  
  
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences", Zurich, March 22-24 1995