Vol. 16, No. 3, Oct-December 2005 

Show Basics: Can Laser Images Float in Space?
By David Lytle, Editor, The Laserist

Blame it on Princess Leia. Ever since Luke Skywalker watched R2D2 project an image of the Princess in mid-air during the first Star Wars movie, people have been asking laser companies to duplicate the effect. Although laser show companies are skilled at many things, breaking the fundamental laws of physics is not one of them. This doesn't mean, however, that they cant' try …

To begin with, let's tackle the basic question: why can't Princess Leia float in mid-air? The problem comes down to the nature of light itself. When we see a laser beam slice through the air, we aren't seeing the beam-we're seeing light reflecting from dust in the air. If the beam has nothing to reflect off, it's invisible to our eye. Of course, there is another way to see laser light. You simply look directly into the laser cavity itself (please don't do this if you value your eyesight!). What you'll see is light emitted from the source. These two examples cover the spectrum when it comes to how the human eye perceives light. To see Princess Leia, her image must either be reflected from a surface (such a projection screen) or emitted from a source (such as a CRT). In either case, a true free space projection is impossible.

So much for the bad news. The good news is that lasers offer a host of ways to create pseudo-3D images that amaze audiences. Some of these ways are old tricks familiar to lighting designers, others are so high-tech that they have yet to be introduced into the marketplace.

The closest thing I've seeing approximating a free-floating Princess Leia was a prototype volumetric projector created by Neos Technologies of Melbourne, Fla. Volumetric projection refers to any technique that creates an image within an enclosed   space. The Neos system worked by using a spinning helix as the projection surface. Spin the helix vast enough and it seems disappears, much like the blades of a high-speed fan become almost transparent when moving. Neos used lasers to project wire-frame images on the surface of the spinning helix, with a computer controlling the precise position of the image as it traveled up, down and around the helix. The spinning corkscrew-shaped helix was enclosed in a one-meter tall box (don't want to loose fingers reaching for the laser image), which made the effect somewhat less than free-floating. This approach is also extremely expensive to implement, so don't expect to see it soon in entertainment applications.

Laser Magic of Playa del Ray, Calif. also uses the volumetric approach for three dimensional laser artwork, but does so using materials that are far easier to work with. Its Laser Tank, for example, uses special microscopic particles suspended in liquid. "The tank acts like a room filled with smoke," said Laser Magic's Barney Kaelin. But unlike room-sized displays, images in the tank appear extremely bright even with low-powered lasers and high ambient light levels. Text, logos and line art seem to mysteriously materialize within the tank, complete with three-dimensional depth as the laser beam passes through the liquid.

One of the oldest laser tricks, but still one of the most effective, is using scrims as projection surfaces. On a dark set, a hanging scrim will not be visible to the audience. When a laser image is projected onto it, the image will appear to magically float in free space. This is much like projecting a movie or video scene-the image is still flat, but good computer animation will make it look three-dimensional. Unlike video, however, the bright, intense laser beam is quite visible on an open-weave scrim. To heighten the effect, I've seen fog added to the set, so that bright shafts of laser light appear in space, with the scanned image floating within the beam pattern.

A variation of the scrim trick is to use a glass surface as projection screen. Viewers will see through the glass, but the glass also reflects images projected onto it (usually from a 45-degree angle off-stage). With the right lighting, the glass is not visible to the audience, and images appear to float in space. This type of illusion dates back to the "Pepper's Ghost" stage trick first shown in 1863.

When it comes to creating life-like 3D objects, there is no substitute for stereoscopic technology. Stereoscopic laser projections require that two distinct images be projected onto the screen, with special glasses channeling one image to the left eye and the second image to the right eye. Sometimes the glasses work on the basis of color (the left eye gets red, the right eye blue or green) and sometimes on the basis of polarization (horizontal and vertical polarized images projected against a silver screen). The idea is to force your brain to process two views of the same 2D object and synthesize a 3D image.

Although special care is needed to setup 3D-laser projection equipment, the effect can be quite striking-even more effective than what I've seen with 3D film. Lightspeed Design of Bellevue, Wash., specializes in high-end 3D laser projections that are combined with computer-generated 3D backdrops. I've seen audience members attempt to catch 3D laser leaves that seemed to be falling in their laps.

Lightspeed took special care in designing its 3D images, starting with a set of geometric equations that determine how a theatre should be optimized for 3D viewing. Using this data, Lightspeed's artists create 3D imagery that appear in the viewer's "personal space." The goal, said Lightspeed Creative Director Robert Muller, is to give each audience member the sensation that they are individually involved in the show. "This is not like movies or television," he said. "The brain reacts to these 3D images as if they were in the viewer's personal space. It changes the whole way someone experiences our shows."

Although striking to see, 3D laser shows are still somewhat rare. "The world of 3D effects is underutilized through the entertainment industry," said Jay Heck, creative director for Laser Fantasy of Bellevue, Wash. Although Laser Fantasy has produced many 3D shows over the years, it has found that the added costs of creating 3D effects (twice the number of laser projectors are usually required, along with more programming time to create the artwork), makes them best suited for high-impact corporate shows and special events. Still, 3D effects are among Heck's favorites, especially when it comes to abstract tunnels that twist and turn, drawing the viewer into a seemingly endless vortex.

As laser display technology advances, we may eventually see Princess Leia flying off the screen to float in mid-air. But until the day comes when the Jedi Knights defeat the laws of physics, we'll have to reach into a bountiful bag of tracks to make audiences open their eyes in amazement and believe they are seeing the impossible.