Calibration of 3D Sensors Using a Spherical Target

With the emergence of relatively low-cost real-time 3D imaging sensors, new applications for suites of 3D sensors are becoming practical. For example, 3D sensors in an industrial robotic work cell can monitor workers´ positions to ensure their safety. This paper introduces a simple-to-use method for extrinsic calibration of multiple 3D sensors observing a common workspace. Traditional planar target camera calibration techniques are not well-suited for such situations, because multiple cameras may not observe the same target. Our method uses a hand-held spherical target, which is imaged from various points within the workspace. The algorithm automatically detects the sphere in a sequence of views and simultaneously estimates the sphere centers and extrinsic parameters to align an arbitrary network of 3D sensors. We demonstrate the approach with examples of calibrating heterogeneous collections of 3D cameras and achieve better results than traditional, image-based calibration.