Video: Wave a high-powered laser around fast enough, and the human eye will perceive an image in the light trail left behind. That’s how laser projectors that cost thousands of dollars work, but it’s also how this cheap, 3D-printed plastic contraption turns a simple laser pointer into a full-on light show.
All the files needed to print one for yourself are available for download over on Thingiverse, including a series of irregularly-shaped cams that move the laser pointer in a very specific pattern as they spin, producing recognisable images such as a star, or The Dark Knight‘s Batman logo. And if you want to design your own pattern, all you need to make the custom disc is a 3D printer — and a healthy confidence in your mathematics skills.