Three Dimensional Images in the Air

Three Dimensional Images in the Air
Visualization of "Real 3D Images" using Laser Plasma

Heliodisplay

The Heliodisplay from IO2 Technology streams three-dimensional images into the air; no screen is needed. Video input from a computer, TV, DVD player, video game console, etc., is projected as a 22- to 42-in. diagonal image that floats above the device. Also, the Heliodisplay is interactive, like a virtual touchscreen: A hand or finger can act as a mouse. No special glove or pointing device is required. Just as you use a mouse to move the cursor on a traditional computer monitor, you can use your finger to move the cursor around the Heliodisplay image.

The Heliodisplay includes patented and patent pending technology to transform normalambient air and display video images into free-space. Some Heliodisplay models are interactive allowing a finger or hand to move images around in the air as if one were grabbing a tangible object.

Holographic Technology

Holograms, do show three-dimensional images. However, you normally have to look at or through a piece of glass (or film) to see the image. If there is any "mid-air" effect, it is because the holographic image appears slightly in front or behind the glass.
The largest hologram is about 1 meter square. The projected image appears to come out about 1 meter in front of the glass. Only two or three people can easily see the image at one time, so it is best suited for a museum-type application.

Holographic Projections

It is possible to project the image which is stored within the holographic glass's film emulsion. This is done by taking a laser beam and projecting it through the glass. The particular view stored at that location can be projected onto a screen or similar surface. As the laser is moved, the image changes since different views are being shown. (An analogy is if you look out a window, through a hole in a piece of cardboard. You can move the cardboard around and see different views or perspectives of the same light coming through the window.)
A projected holographic image is exactly the same as projecting a slide or a movie. The projected image is shown in two dimensions on a screen or flat surface. As with a slide or movie, you can project into a fog, cloud or other volume, but as with a slide or movie, you will get a shaft of light.

Stereoscopic 3D

For projecting large 3D images to a crowd, the best current technology is stereoscopic 3D. This is what is used at theme parks such as Walt Disney World ("Captain EO", "Honey, I Shrunk the Audience", "Muppet Movie") and Universal Studios ("Terminator 3D"). It is also used at IMAX Solido movie theatres.

All stereoscopic 3D techniques require the audience to wear special glasses. Each eye must see a different view. Four common methods are:

• Anaglyph or color (left eye red, right eye blue or green)
• Polarized (left eye looks through vertical polarizing film, right eye looks through horizontal polarizing film)
• Alternating-field (LCD "shutter" glasses block the right eye when a left-eye frame is being displayed, and vice versa)
• Chromatic displacement or ChromaDepth® (flat holographic "prisms" displace colors so red looks closest and blue farthest away)

               The 3D effect, if done properly, can be quite striking. But again it is not a mid-air projection. It looks more like viewing a theatrical stage.

               There are many sources for more information on stereoscopic 3D.

               Pangolin's Lasershow Designer 2000 software can do stereoscopic 3D laser shows, should you need that capability. The projectors are complex and require expertise in design and operation. A good example of the results are the stunning 3D laser-and-slide multimedia shows from our client Lightspeed Design.

Projection onto Hidden Surfaces

One old trick in the laser field is to hang a dark or black scrim (loosely-woven cloth) above an audience in a dark room. When the laser hits the scrim, there will be an image appearing to hang in mid-air, since the scrim cannot be seen.

               The image itself will be flat, just like a slide or movie image.

               You can get an illusion of a 3D object in space by projecting an animation where a 3D object, shot against a black background, rotates or moves so you can see all sides. But this is merely an illusion whose quality at best is pseudo-3D.

               If a sequence of scrims are hung, then there is a 3D effect of a series of floating objects. Of course, since the same image hits all scrims, the floating objects are all the same.

Other Techniques

At Walt Disney World's "Haunted Mansion", there are some elaborate 3D illusions. Many visitors think they are holograms, but they are not.

               One illusion uses a pane of glass tilted at a 45 degree angle. A manikin is behind the glass and another is at the side. By varying the lighting, it is possible to show each manikin separately, or to superimpose both of them. A disadvantage of this is that only a few visitors at a time can see the illusion; this is why the ride's cars transport visitors past the glass.

               This general class of illusions -- reflections off tilted glass -- is known as "Pepper's Ghost" after a stage trick first presented in 1863.

               Another illusion seen in the "Haunted Mansion" uses a "screen" that is a mold of a face. When a film of a person talking is projected onto or through the mold, it appears that there is a 3D head.