Compact scanning confocal chromatic sensor enabling precision 3-D measurements

This paper proposes a compact and lightweight scanning confocal chromatic sensor (SCCS) for robot-based precision three-dimensional (3-D) surface measurement applications. The integrated system design includes a 2-D fast steering mirror (FSM) to manipulate the optical path of a high precision 1-D confocal chromatic sensor (CCS). A data-driven calibration procedure is used to accurately combine the FSM deflection angles and the correspondingly measured distances to the sample surface in order to obtain a correctly reconstructed 3-D image. Lissajous scan trajectories are applied to enable efficient scans of the sample surface. The SCCS provides 3-D images at frame rates of up to 1 fps and a measurement volume of 0.35 × 0.25 × 1.8 m m 3 , as well as the measurement of arbitrary regions of interest. Using a calibration standard including structures with defined sizes, the lateral and axial resolutions are determined to 2.5 µm and 76 nm, respectively.