WHY THIS MATTERS IN BRIEF
- Everyone loves holograms, or they think they do, because until now most holograms have relied more on parlour tricks than actual science and technology to work, but that might be about to change
Every science fiction film ever created, and probably even the ones that were created before TV even existed, has included some form of hologram – such is their fame. But decades on, while we’re getting closer to being able to play with holograms in our living rooms, the reality is they’re still probably decades away. Sure there are holographic tables and smartphones but you could argue that they’re simply good magicians tricks, and imperfect.
Now though researchers at the Digital Nature Group (DNG) in Japan have found a way to use lasers, mirrors and cameras to create 3D interactive holograms comprised of tiny points of light called “Voxels.”
The Teams Interactive Hologram
Using femtosecond lasers, a femtosecond is a quadrillionth of a second, the teams lasers transmit bursts that last 30 to 270 femtoseconds, the team were able to make holograms that were safe to touch, and the images are 3D with resolutions up to 200,000 dots per second. The voxels are light emitted by plasma that’s created when the laser’s focused energy ionizes the air.
When touched, the laser feels like sandpaper, says principal investigator Yoichi Ochiai, although some participants thought the plasma felt a little like a static shock, so it’s evident there’s some work to be done there – after all we don’t all want our new holographic interfaces to shock us all the time.
This isn’t the first attempt at using femtosecond lasers to form air plasma, says Chunlei Guo, professor of optics and physics at the University of Rochester, but he believes his study could help in designing future femtosecond laser displays. Although previous studies have used nanosecond and femtosecond lasers to create images, the DNG researchers say preceding studies haven’t achieved resolution this high, and the results burnt human skin, and we definitely don’t want that.
Since the lasers fire at such a high speeds, they’re able to react in real time, and researchers have demonstrated its ability to make usable holographic checkboxes and hearts that break when touched.
To create their hologram, researchers fired their femtosecond laser through a spatial light modulator, which continues the beam through a series of lenses, a mirror and a Galvano scanner, which positions a mirror to precisely direct the laser beams. A camera underneath the hologram captures user interaction, allowing the dots to respond to being “touched.”
Ochiai says the most surprising thing he realised was that plasma was actually safe to touch in this application, making the hologram exponentially safer than previously thought.
The key to making these holograms safe though is the shorter duration of the laser’s bursts. In tests, if the lasers fired in more than two second bursts, they burnt the leather researchers used to simulate skin, but, if they transmitted at 50 milliseconds to 1 second bursts instead, the leather was unscathed.
Ochiai says this is machine is just a proof of concept, and now his team will work to make the holograms larger – at the moment they’re limited by the size of the spatial light modulator, which they maxed out with this experiment, but meanwhile the femtolaser could transmit up to 7W, and the teams 1 cubic centimeter experiment only used 1W of the laser’s power.