Plenoptic cameras as depth sensors for the precise arm positioning of planetary exploration rovers

Kurzfassung

Many robotic missions for planetary exploration use an arm to position scientific instruments close to or even on an object (e.g. a rock) for data recording or sampling. Images and depth maps from cameras can help to improve the accuracy and reliability of the instrument positioning by increasing the amount of information and the situational awareness that is available to the operator. Plenoptic cameras are a new type of passive camera system that provide 2-D images and depth maps from a single camera and with a single shot. Due to their recording concept, plenoptic cameras allow to decrease the volume, mass and complexity of a depth estimation device that is mounted to a robotic arm. Hence, they are a promising alternative to other available depth estimation devices such as stereo cameras or active cameras (e.g. Time of Flight cameras or LIDARs). This work presents the concept of using plenoptic cameras for precise robot arm positioning in the context of robotic planetary exploration, together with a set of experimental results. The experiments use a plenoptic camera mounted to a robot arm, investigating the potential range, accuracy, precision and density of plenoptic depth measurements. The results show the utility of this new type of sensor for precise scientific instrument positioning. A depth range of up to 75% of the distance between the main lens and the object was achieved, using a maximum error tolerance of 20% relative to the ground truth. Within the depth range, it was possible to reach a depth accuracy of up to 0.5 mm, a precision of ±0.2 mm and a depth density of 350 pts/mm2 .