Pan-Tilt Unit

The scanning rangefinder must be rotated (or translated) to acquire a 3D data set. To rotate the device, we attached it to a pan-tilt unit (model PTU-46-70) from Directed Perception, Inc (see http://www.DPerception.com for more information). We do not require the tilt operation for our task, and fortunately it can be disabled. The panning unit attaches to a computer with a standard serial cable. The panning unit has a claimed position resolution of 0.771 arc minutes, allowing us to make nearly 80 scans per degree. We chose this model over the 46-17.5 for the higher positional resolution. It also has the advantage of more power and slower velocity since lower gearing is used. The pan-tilt unit is very easy to interface to. The rangefinder with the scanning mirror and pan-tilt unit are all shown in figure 5.