How a Laser Projector Works

A show laser projector draws a picture with one moving dot. Red, green and blue lasers make the colour. Mirrors combine them into a single beam. Two small mirrors on fast motors, called galvos, steer that beam. One moves it left and right. The other moves it up and down. The dot moves so fast that your eye sees a solid line, a shape or a whole pattern.

Use the model above. Drag to turn it, scroll to zoom, and tap a part to see what it does. You can follow the beam colour from the red laser, through the two colour mirrors, to the output. You can also slow the scanning down to follow the single dot. A real projector redraws the whole shape many times a second.

Try the fault option as well, because it is the part that matters for safety. If the mirrors stop moving, the dot stops moving too. A beam that was spread across a shape becomes a still beam at full power, which is far more hazardous. That is why a show needs e-stops, masks and a scan-fail safeguard, and why the safeguard is only a backup. [cl. 3.39, 9.6.1]