Range Extension for Large-Scale Robotic Precision 3-D Measurements in Vibration-Prone Environments

This article presents a range extension concept for a high-precision robotic inline 3-D measurement system. A scanning confocal chromatic sensor (SCCS) is integrated with a magnetically levitated and actuated measurement platform (MP) for the acquisition of 3-D images with submicrometer resolution, enabled by means of active sample-tracking to compensate for relative motion between the SCCS and the sample. Based on an intermediate range extension approach, the lateral scan area is pre-extended to enable a robotic repositioning of the 3-D measurement module, ensuring sufficient overlap regions between the individual 3-D image frames. Experimental results show that the proposed concept extends the 3-D measurement modules' measurement range by about 80% of the lateral scan area within an acquisition time of about 90s. Range-extended 3-D measurements directly in a vibration-prone environment reveal that 97% of disturbing relative motion between the SCCS and the sample are compensated by the active sample-tracking approach. In this way, lab-like conditions for the SCCS are established directly in an industrial production line and, improving the measurement error by three orders of magnitude down to several tens of nanometers.