Less expensive galvanometers (or alternatives)
The voice coil/galvanometer acting as the head actuator of a hard disk drive could be a solution. They are ubiquitous, can be scavenged at zero cost from old drives and have an insanely fast response for a mechanical part (as they are optimized for low seek time).


In order to use one, I would remove any encumbering area of the aluminum case, get rid of the magnetic R/W head and associated wiring, mount a reflector/prism to the pivot of the arm and wire the coil directly to a driver: either an audio amplifier for testing, or if better control (closed loop position control and/or asymmetrical movement) is necessary, a H bridge circuit (could be implemented with discrete transistors, a ready-made chip such as the SN754410, or even the arduino motor shield) pulse width modulated with a microcontroller.







simulate this circuit &ndash; Schematic created using CircuitLab

For mass production using scavenged parts from random e-waste is not really an option, but you could probably source something similar from china, or even make your own design.