Lasershow

Have you ever fancied some cool laser effects, but couldn't afford to buy commercial devices? Me too ;) So a friend of mine, Yosh, and I started looking for concepts on our own. Here's what we ended up with:

The idea

The idea is to glue tiny mirrors to the axes of two DC motors, and to make them oscillate by applying an AC voltage.

1. The mirrors

The mirror controlling the horizontal position of the laser beam is 0.8 cm x 1.0 cm, the one for the vertical position is 2.5 cm x 0.7 cm.
You probably won't have mirrors of the right size and shape lying around, so you need to cut a larger mirror (in our case we used a pocket mirror). This isn't really fun because the only law that seems to be valid when cutting glass is Murphy's. First you carve a line onto the surface of the mirror using a glasscutter - most effectively from border to border -, then you apply force and hope the mirror breaks where you want it to (don't forget to swear if it doesn't ;) ).

2. The motors

We used motors from old cd drives

The mirrors are glued to the axes of the motors using universal adhesive.

3. The signal

The first and simpler question is how to generate the signal that makes the laser beam dance. The common methode is to use a computer with appropriate software, but be careful to use a soundcard capable of generating signals at about 100Hz and even lower with reasonably good quality. Almost all cheap soundcards will fail these requirements, and give poor results! We used an old Soundblaster Live! card with initial success. As for the software, I wrote a simple signal generator that fitted our needs, but isn't really worth being publish here. Search the web for a signal generator.

The next task is to find something to amplify the signal. We can't help you there, because we tried a couple of amps ranging from cheap low quality stereo sets to high quality hifi amplifiers and were surprised that some low quality devices performed even better than some of the hifi amps. We finally ended up with an old cassette recorder ;).

The wires

The amplifiers output is to be connected directly to the motors. It's as simple as this ;).

4. The show

Direct the beam of a laserpointer onto one of the mirrors as show in the pictures, dim the light and there you go. If you apply sinewaves with different frequencies and/or phase you can get beautiful Lissajous figures, like these:

and even moving figures:

lissvid1.avi

lissvid2.avi

lissvid3.avi

The vision

After a while watching lissajous figures becomes quite boring, so why not try to display other figures. Some exiting pictograms or even text would be cool. In order to try this out I started coding a piece of software generating the signal needed. But while the oscilloscope showed beautiful triangles, rectangles and other polygons, the laser device displayed a lot of crap. Probably the coils in the motors (or perhaps even the amplifier) distorted the signal. Our efforts to eleminate the distortion by fitting the input signal to the output effect failed completely.

Anyway, if you find a new interesting way of using this device or modifying it, send us a mail and tell us your experience.

email address: ey enn dee e
thirteen at gee emm ex dot dee e