Well, I know this is an interesting subject, and I hope to be not
pestering people's life here.  It is very common to feel attraction for
this kind of experiences, reflect light or laser beam, and play with
music, images, letters and so on. It is very exciting, and very much,
mainly for hobby people, a lot in this list. Using a PIC to control it
should be hours taking adventure.  Some last recommendations to who
wants to go for this challenge, and to reduce several other posts about
it, here it goes:

1) There are some listings in the net just dedicated to this subject,
just search for light show, or laser show.

2) What you need is just few degrees of a mirror movement, since it just
means a big movement when projected at meters of distance.

3) Forget to use speakers with mirrors or something other miraculous
solution, it simply does not work.  Speaker's cone movement does not
creates an angle, it moves straight, even in the round movement close to
the outside of the cone is very difficult to build it, frequency
response is not linear and other problems. Straight movements doesn't
amplify the movement, just transport it. If the cone moves straight
1/8", this would be what the laser beam would move at the wall.

4) Stepper motors are pretty nice to test, play and see something, but
it is not fast enough even to write a stable low flickering "HI" in the
wall.  Also, forget cheap stepper motors with more than 3¡ per step, you
would not have resolution, and the image would "open" too wide in the
wall.  Using a 3.7¡ (if I remember well) per step motor with letters
with 8 steps it means more than 24¡ for a whole letter, it opens half
meter for each meter distance from the wall to the laser. 1:10 relation
is good, so less degree per step and less steps per image or letter.

5) Forget about using a reduction gear-box at the stepper motor to
reduce the angles/step, it would generate slack, image shaking and will
reduce mirrors speed, terrible idea.

6) Several other tests were done;
	
Solenoid attracting pins with mirrors hinged to it.

Solenoid bending a thin reflective metal place.
	
Can of black oil with speakers attached on the bottom and sides,
generating ondulations on the oil surface, laser reflects on it,
creating a somehow nice patterns, dirty job and not useful at all. 

None of above solutions can't even get a little close to what a galvo
can do.

Somebody once said that compressing water inside a glass could change
its reflective light angle, since its mass would change, so the angle, I
don't know what the guy was thinking, possibly control pressure inside a
bottle, ... not fast enough.

It will be the day that we will see a light beam angle controlled by non
mechanical ways.

If you need to buy some laser pointers to play and can't find in your
neighborhood stores, take a look at my webpage (I sell them) <g>.

wagner.
http://www.ustr.net