Integrated compensation-based laser sensor system for in-plane and out-of-plane target tracking

This paper presents the development of a compensation-based laser sensor system, capable of sensing in-plane as well as out-of-plane displacements of a target. The sensor design integrates principles of laser triangulation and objective laser speckle measurement into a single device and provides an in-plane and out-of-plane resolution of 3 µm and 1 µm, respectively. The compensation-based operation keeps the variation of distance and lateral position relative to the target close to zero by actively following the target motion using feedback control. This enables a large operation range of the resulting sensing and tracking system, limited only by the range of the actuation system. Accurate tracking of target motions is demonstrated in an area of 1×1mm² with a small remaining spatial rms tracking error between 8.75 µm and 13.25 µm.