Calibration and development for increased accuracy of 3D range imaging cameras

Range imaging has become a valuable technology for many kinds of applications in recent years. Numerous systematic deviations occur during the measurement process carried out by available systems. These systematics are partly excited by external and partly excited by internal influences. In this paper the following investigations will be presented in closer detail. First the statistics of the distance measurement of the analyzed range imaging cameras SwissRanger (TM) SR-2 and SR-3000 will be shown. Besides the question if the measurements are Gaussian distributed, the precision of the measurements will be shown. This aspect is of importance to answer the question if the mean value of a series of measurements leads to more precise data. Second diverse influencing parameters like the target's reflectivity and external as well as internal temperature are aimed. The dependency of the distance measurements with respect to the amplitude is one of the main aspects in this paper. A specialized set up has been developed in order to derive experimentally the detailed correlation, which is expressed in terms of linearity deviations. Besides the results of some specific aspects, an overview of the recommended calibration procedure is given. The reader of this paper will be enabled to understand the calibration steps needed to gain highly accurate data from the investigated range imaging cameras. Due to the fact that range imaging cameras are on their way to become state of the art in 3D capturing of the environment, it is of importance to develop strategies for the calibration of such sensors in order to enable users to revert to these principles for the sake of simplicity. Therefore, these strategies long for sophisticated approaches and reliable results of investigations. This paper will introduce such an approach to be discussed within the scientific and user environment. One of the main achievements of this work is the introduction of a method to significantly decrease the influence of temperature on the distance measurements by means of a differential measurement principle setup. The verification of the functionality is presented, as well.