Most laser scanners use moveable mirrors to steer the laser beam. The steering of the beam can be "one-dimensional", as inside a laser printer, or "two-dimensional", as in a laser show system. Additionally, the mirrors can lead to a "periodic" motion - like the rotating "mirror polygons" in a barcode scanner or so-called "resonant galvanometer" scanners - or to a "freely addressable" motion, as in servo-controlled galvanometer scanners. One also uses the terms "raster scanning" and "vector scanning" to distinguish the two situations. To control the scanning motion, scanners need a rotary encoder and control electronics that provide, for a desired angle or phase, the suitable electric current to the motor or galvanometer. A software system usually controls the scanning motion and, if 3D scanning is implemented, also the collection of the measured data.