Apparatus for mapping includes a radiation source, which is configured to emit at least one beam of radiation, and a detector and optics, which define a sensing area of the detector. A scanner is configured to receive and scan the at least one beam over a selected angular range within a region of interest while scanning the sensing area over the selected angular range in synchronization with the at least one beam from the radiation source. A processor is configured to process signals output by the detector in order to construct a three-dimensional (3D) map of an object in the region of interest.