Holograms You Can Touch Developed

Sunday, July 5, 2015

Holograms You Can Touch Developed

The interactive holograms featured in films like Iron Man and Big Hero 6 may be closer to reality thanks to work done by Japanese researchers with femtosecond lasers. 

Researchers in Japan have created a mid-air 3D holographic plasma display that also features haptic feedback.

"This study is the first step to discuss and design laser-based aerial volumetric displays," write the researchers.

The system, demonstrated in the video below, works by way of using a femtosecond laser to turn small pockets of air (voxels) into plasma.

"This study is the first step to discuss and design laser-based aerial volumetric displays."

The holographic system, which will be presented at SIGGRAPH 2015 next month, can render up to 200,000 voxels per second, but the physical size of the display is limited to about a cubic centimeter.

The researchers commented on the details of the theoretical principles, system setup, and experimental evaluations, and also discusses the scalability of the system, along with limitations, and applications. "Although we focus on laser-induced plasma, the same considerations can be applied to
other emission techniques such as fluorescence and cavitation," they write.

A femtosecond laser is a laser that fires for a short burst—on the order of one quadrillionth of a second. The laser hits an atom or molecule, causing an electron to become ionized and then the electron loses its extra energy in the form of a photon that is emitted as visible light.

Fairy Lights in Femtoseconds

To transform the single plasma dot into a full 3D display, the researchers passed the laser through a spatial light modulator (SLM) connected to a PC to create the hologram, and then a galvano scanner and varifocal lens to "draw" each voxel with specific X, Y, and Z coordinates.

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One of the more intriguing aspects of the 3D display is that it also incorporates haptic feedback. According to the research paper, when you touch one of the voxels, "shock waves are generated by plasma ... the user feels an impulse on the finger as if the light has physical substance." The researchers don't go into any further detail on the topic, however.

The paper also notes that using a femtosecond laser (as opposed to a picosecond or nanosecond laser) is one of the novel aspects of the system. Because the laser bursts are so short, the plasma is not that energetic, and so it's safe to touch. The researchers also tested a nanosecond laser, but found that it burned a piece of leather within 100 milliseconds.

The femtosecond laser setup appears to be safe and doesn't cause any skin damage when a user touches the display, though you still shouldn't look into the laser source. 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.

Tangible Hologram

For now, the holographic plasma display is too small to be of much use—and perhaps more importantly, the equipment used to produce the display is too large and expensive for anything outside of the lab. The principles are all quite sound, though, and there's a lot of interest in free-space display technologies that don't require some kind of screen or other medium to project the image onto.

SOURCE  Popular Science

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