Pan-Tilt Unit.

A pan-tilt unit from Directed Perception [17] controls the orientation of the scanning plane. The rangefinder is placed on the pan-tilt unit such that the position where the laser reflects off the scanning mirror is on the panning axis. The panning device has 14,000 steps in 180$^\circ$; thus, to acquire samples every milliradian, we typically move 3 or 4 steps between each successive scan.