Touchable holography

"It's the sense of touch. In any real city, you walk, you know? You brush past people, people bump into you. In L.A., nobody touches you. We're always behind this metal and glass. I think we miss that touch so much, that we crash into each other, just so we can feel something."

[Graham Waters - Crash 2004]

In 2007 screening of Stanislaw Lem's Ijon Tichy: Raumpilot - Die Sterntagebücher airs on german TV. In the first episode world famous space pilot, galactic diplomat, discoverer and hero of the cosmos Ijon Tichy is on a space journey to far distant planet Eggman for quite an urgent meeting. Due to traveling night and day he falls asleep and his spaceship collides with a piece of space junk. He decides that he couldn't go like this any longer and constructs an electric colleague to help him on board so he hasn't got to do all the work by himself. He calls his invention "Analoge Halluzinelle", because she is an holographic projection. Her image isn't very stable. So Ijon Tichy allots her the task to take care for the fine adjustment. Therefore he passes an antenna to her. She tries to grab it but due to the fact that she consists of nothing but light, she can't hold. The same would happen for he tries to touch her. His hand would go right through without touching and feeling.

"Mid-air displays which project floating images in free space have been seen in SF movies for several decades [Rakkolainen 2007]. Recently, they are attracting a lot of attention as promising technologies in the field of digital signage and home TV, and many types of holographic displays are proposed and developed. You can see a virtual object as if it is really hovering in front of you. But that amazing experience is broken down the moment you reach for it because you feel no sensation on your hand.

Our objective is adding tactile feedback to the hovering image in 3D free space. One of the biggest issues is how to provide tactile sensation. Although tactile sensation needs contact with objects by nature, the existence of a stimulator in the work space depresses the appearance of holographic images. Therefore some kind of remote-controlled tactile sensation is needed. That is achieved by our original tactile display [Iwamoto et al. 2008]"

It seems that reconstructing a real three-dimensional image, holography simultaneously arises a phantasm and a yearning to touch and to feel as well. Just think of Robert Schinella's hologram "Hand in Jewels" exposed at Cartier at the 5th Avenue in New York City in 1972. And think of all the passers-by trying to grab it.

But today holography seems to reach a point where possible abilities catch up phantasms.

"Up until now, holography has been for the eyes only, and if you tried to touch it, your hand would go right through, but now we have a technology that adds the sensation of touch."

(Hiroyuki Shinoda, Tokyo University, 2009)

To make holograms touchable the japanese scientists add a tactile feedback to the hovering image in 3D free space.

Three things are needed to give the sensation of touch to the user's hand:

First of all of course a holographic display, that provides floating images from an LCD using a concave mirror.

Second to that an airborne ultrasound tactile display is used which provides a tactile sensation onto the user's hand. "It utilizes the nonlinear phenomenon of ultrasound; acoustic pressure. When an object interrupts the propagation of ultrasound, a pressure field is exerted on the surface of the object." (Shinoda, 2009)

Thirdly a Nintendo Wiimote provides the exact 3D position of the user('s hand). "Owing to this hand tracking system, the users can handle the floating virtual image with their hands." (Shinoda, 2009)

As great as the field of applications of holography have been prior touchable holography as great could even be the field of applications of touchable holography itself. It could be useful for video games, 3D CADs, redefining interfaces to move from actual physical switches to virtual holographic ones, which includes a hygienic consideration as well as an eco-friendly one. With buttons appearing when one needs them an disappearing when not.