Experimental and Theoretical Investigation of Correlating TOF-Camera Systems

This thesis investigates Time-of-Flight (TOF) 3D imaging systems. A mathematical model is developed to predict the systematic errors and statistical uncertainties of such cameras. In order to determine the errors experimentally and to test the model, a custom experimental setup has been built for this work. Chapter 2 provides a detailed discussion of this experimental setup. Three camera systems are investigated experimentally: the PMD[vision] 19k, the SwissRanger SR-3000) and the Effector O3D. All cameras have a maximum measurement range of 7.5 m. This thesis discusses the experiments, the results and the implication of this tests and concludes with a critical discussion of the results. Possible ways to correct the revealed systematic errors is presented in the discussion. This work reveals three common systematic errors: the variation due to the anharmonic LED modulation provokes a periodic depth error of around 80-200 mm (depending on camera), the inhomogeneity of the pixels accounts for around 20 mm and the constant offset depending on the integration time was found to vary between 35-100 mm. The statistical variances at 30% of the maximum amplitude was found to be between 9 mm and 23 mm. Moreover, a technique to detect and remove overexposed pixels whenever possible is presented. With the proposed calibration, the absolute systematic error could be reduced in a sample calibration for the SwissRanger SR-3000 from maximal 300 mm (standard deviation: 40.81 mm) to below 16 mm (standard deviation: 3.16 mm) for all well exposed pixels. This work has been done within the framework of the Lynkeus-3D project (http://www.lynkeus-3d.de) supported by the BMBF (Bundesministerium für Bildung und Forschung) and in close cooperation with industry partners. The investigations of this work led to the detection and the mending of a construction error in one of the camera systems