A holography technique developed at Brigham Young University enables the creation of light-based animations that can be seen with the naked eye, without a screen. Electrical engineering professor Dan Smalley and his team garnered international attention in 2018 when they demonstrated the ability to draw screenless, free-floating images in free space, called optical trap displays. That technique uses photophoretic trapping, and traps a single particle in the air with a laser beam. The particle is illuminated by visible lasers and then moved around, leaving behind a laser illuminated path that floats in the air. The current research development builds on that foundation to now produce simple animations in the air. The researchers demonstrated the technology using miniature models of Star Trek spaceships. Shown here is a Klingon battle cruiser taking a hit from a photon torpedo fired by the starship Enterprise, simulated with laser light. Courtesy of Brigham Young University. “What you’re seeing in the scenes we create is real; there is nothing computer generated about them,” said Smalley, lead researcher of the project. “This is not like the movies where the lightsabers or the photon torpedoes never really existed in physical space. These are real, and even if you look at them from any angle, you will see them existing in space.” To demonstrate the principle, the team created virtual stick figures that walk in thin air. They were able to demonstrate the potential for interaction between virtual images and humans when a student placed their finger in the middle of the volumetric display, and then filmed the same stick figure walking along and jumping off that finger. The latest work overcomes a limiting factor to optical trap displays, in which the technology is unable to show virtual images, a limiting factor in all volumetric displays. The team shows that it’s possible simulate virtual images by employing a time-varying perspective projection backdrop. “We can play some fancy tricks with motion parallax and we can make the display look a lot bigger than it physically is,” researcher Wesley Rogers said. “This methodology would allow us to create the illusion of a much deeper display up to theoretically an infinite size display.” The research was published in Scientific Reports (www.doi.org/10.1038/s41598-021-86495-6).