Laser Engraving
In laser engravers, a mirror galvanometer is a series of mirrors in the laser head that move extremely fast to manipulate the path of the laser. A small rotation of 10 degrees at the head is enough to produce 1 3/4" inch of movement at 10 inches. It is also used to trace out the laser paths before engraving or cutting.
The beam quality for 20W, 30W, and 50W lasers is less that 1.5 M2, while it is less then 1.8 M2.