Lissajous Laser

Essential Ingredients

  • 2 motors
  • 2 round mirrors
  • 1 sheet of glow-in-the-dark vinyl
  • 1 UV laser
  • 2 potentiometers

Basic Idea

A UV laser beam shines upon a glow-in-the-dark surface, causing it to glow. The path of the laser is interrupted by two mirrors that each rotate about their center by a motor. Because the plane of the mirror is not exactly perpendicular to the axis of rotation, the exiting beam's path rotates. The rotations of both mirrors add together to create Lissajous figures on the glow-in-the-dark surface.

Design tips

  • Laser alignment is difficult. It is easiest to start from the laser and make adjustments from beginning to end, not the other way around.
  • The laser path that seems easiest to deal with is the shape of a Z, with the corners of the Z being where the mirrors are.
  • When aiming the 1st reflected beam onto the 2nd mirror, turn the 1st motor on. You should see a dim circle appear on the 2nd mirror. Get the whole circle on the mirror. If it's too big a circle, either move motor #2 closer to motor #1 OR the plane of your 1st motor's mirror is too far off from perpendicular to its axis of rotation.
  • Pick power supplies, motors, and potentiometers that match each other, so that the potentiometer--turning all the way from left to right--corresponds nicely to a zero to full speed rotation of the motor.

Troubleshooting

  • Check all electrical connections
  • Use your finger to interrupt the beam so you can follow its path.