The x-y scanners are used with lasers to generate graphic images. They basically consist of an electromagnetic coil, similar to those found in analog meters. Instead of a meter needle to indicate current, voltage or whatever, a lightweight mirror is attached. This arrangement is usually called a galvanometer or galvo for short. When current is applied, the meter movement rotates the mirror, usually only a few degrees. This will allow the laser beam to be moved ("scanned") from side to side. If the side-to side moving beam is allowed to strike the mirror of another of these devices at 90 degrees, it will allow the beam to move side-to-side (x) or up-and-down (y). High speed galvos are usually quite expensive and require special driver circuitry to make them operate. General Scanning and Cambridge Technology make very high quality galvos for professional use.
Here is a link which better describes the scanners and shows how to make a do-it-yourself loudspeaker-type scanner.
**broken link removed**
JB