360-degree 3D autostereoscopic display

Recently several devices and technologies have been introduced using a three-dimensional display (3D smartphone,

3D computer display, touchable holography). Actually they are using two-dimensional displays to generate the

illusion of a three-dimensional image. But on this years SIGGRAPH japanese company SONY introduces a 3D display

wrapped in a cylinder that is ten inches tall and has a diameter of five inches. The prototype not just allows to reach

into the display and turn objects, but it also allows to walk around and watch it from all angles.

Airborne ultrasound tactile display

About one year prior Hiroyuki Shinoda adds the Wiimote hand tracking system to make up touchable holography preliminary, he presents an airborne ultrasound tactile display at SIGGRAPH 2008 (International Conference and Exhibition on Computer Graphics and Interactice Techniques), which ought to be introduced a little more detailed in this entry, as the second method of touchable holography - excluding the projection of a 3D floating image.

Airborne ultrasound tactile display radiates airborne ultrasound and produces high-fidelity pressure fields onto a user's hand. This method is based on a nonlinear phenomenon of ultrasound. Unlike air-jet, generated fields of static pressure can be localized and do not cause unnecessary vibrations. When this propagation of ultrasound is interrupted by an object, a pressure field is exerted onto its surface. This pressure is called acoustic radiation pressure. The spatial distribution of ultrasound is controlled by multiple ultrasound transducers, based on wave field synthesis techniques. Using these techniques, various patterns of pressure field can be produced in 3D free space. Airborne ultrasound can be applied directly onto the skin without the risk of penetration. Tactile feedback is provided to the users' hand without requiring gloves or any other mechanical attachments.

Airborne ultrasound tactile display

Tactile feedback is superimposed over 3D graphics projection. The generated pressure field corresponds with the 3D virtual image. The sensation of touch would be broken, for the synchronization between pressure field and image doesn't work.

The goal of this technique is to considerably improve the usability of systems, which enables users to manipulate 3D graphic objects with their hands. It can find application e. g. in video games or 3D modeling software. "It might also be useful to manipulate small particles or probingg the surface of an object to measure the viscoelastic properties of the object from a distant point."

Hand tracking

Giving a tactile sensation to holography, besides of course a projection of a floating three dimensional image, among others a tracking system is needed, which works as an interface between hologram and human. As it is shortly shown in the attached video in entry Touchable holography a Wii Remote can be used as a simple tracking system.

Johnny Chung Lee gives a little more detailed view on how the Wii Remote tracking system works. Even he applies it in another context than holography, that ought to be shown below, because the mechanics behind it is of the same kind.

Wii Remote tracking system

"While camera-based and marker-less hand tracking systems are demonstrated these days, we use Wiimote (Nintendo) which has an infrared (IR) camera for simplicity. A retroreflective marker is attached on the tip of user's middle finger. IR LEDs illuminate the marker and two Wiimotes sense the 3D position of the finger. Owing to this hand-tracking system, the user can handle the floating virtual image with their hands."

To give a more complete understanding of how touchable holography - as Shinoda Lab from University of Tokyo presents it at SIGGRAPH 2009 - works, another entry about airborne ultrasound tactile display is added.

The snippet attached below wants to illustrate what Johnny Chung Lee is talking above about Minority report.

Minority report (2002)

This movie forestalls the technology of hand tracking several years prior it finds application in combination with holography. So to say the technology catches the phantasm of user interface including hand tracking.