Fast and precise scribing or writing of information bacame an issue parallel to the computer.
Laser printers are replacing the existing printer technology. Another field of application is the scribing on objects of mass production. In this case powerful lasers are used to scribe permanent information into metal, plastic, paper, etc.
To generate arbitrary patterns the laser beam must be deflected in two orthogonal directions as it is known from TV or oscilloscopes. In general there are two main fields of applications: fast material processing and entertainment. For the material processing, it is necessary in almost all cases to focus the laser beam onto the surface to be processed. With simple lens systems this cannot be achieved since the location of the focus lies in the plane of a sphere. A special optical system has been designed to image the focus always in a plane and is termed as f-θ lens system. For entertainment like laser light shows, etc. a focusing of the beam is not required. However, for both applications the same beam deflectors, galvo scanners are used. The name comes from the historical galvanometer, a moving coil instrument where a mirror was attached to the torsion band of the coil. Such instruments were used to demonstrate slow varying electric currents. The galvo scanner uses the same principle, however, they are designed for rapid movement of the attached mirror. Instead of using a torsion band, electromagnetic forces are applied.

Principle of operation

The beam of the laser (LS) is directed to the first galvo (GX) which mirror is set to 45°. The beam leaves the mirror perpendicular to the incoming beam and hits the second galvo (GY). The mirror is set in such a way that the beam leaves the galvo (GY) with an angle of 90° to the incoming beam. When the galvo GX starts to oscillate, the output beam is fanned out in a horizontal plane. If the galvo (GY) would oscillate a beam fan in the vertical plane is generated. Depending on the input signal of each scanner arbitrary patterns can be generated. Since the galvo is kept in position by electromagnetic forces it requires a substantial amount of electrical power which must be provided by sufficiently designed power supplies. Professional galvos as also used in this project are equipped with angular encoders which are part of a closed loop control system in order to reach the desired movement.