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Show Basics: Laser Show Primer

Atmospheric Effects Are True
Showstoppers, Indoors Or Out
By Tim Walsh, Laser Spectacles

The laser effect that most causes audiences to gasp with wonder and delight is the experience of seeing laser beams move through open air. These effects are called “atmospheric” because they rely upon beams sculpting the atmosphere of the venue, with no projection screen involved. Atmospheric and beam effects are a true 3D experience, with no tricks or 3D glasses needed. There are, however, some basic guidelines to producing a successful atmospheric laser show. In this article I will discuss how venues can maximize the impact of atmospheric displays and I’ll analyze the different types of effects commonly used to reach out and “touch” the audience.

The first thing to remember about laser beams concerns visibility: a laser beam passing through perfectly clean air will be invisible because there is nothing to reflect or scatter the light. To help make the beams visible indoors, laserists often introduce particles into the air, usually using theatrical fog machines. Beams passing through water fountains or mist will also create beautiful sparkling displays (be prepared for the high humidity that comes with this type of effect). Outdoors, the use of higher powered lasers combined with the normal dust found in the air means that beams are usually visible in the night sky.

The second component of beam visibility has to do with sight lines. If a laser beam is coming toward the viewer, the apparent brightness of the beam is increased. Beams that are perpendicular to the viewer are perceived as much less bright. Those going away from the viewer vary in apparent brightness depending upon the ambient light in the background. For creating successful beam shows, it is wise to plan the display as coming towards the audience.

The last element to consider is ambient light. The easiest and most cost-effective way to increase the brightness of an atmospheric laser display is to make the venue completely dark. This lets the laser beams be experienced at their full intensity. Keep in mind that the audience’s eyes may need up to ten minutes to adjust to the dark; after that they can perceive laser lights much more intensely. Check a potential outdoor show site at night to find ambient light problems. Street lights or security lights from blocks away may be shining directly at the audience. I have even seen automobiles being directed by security police during a show in such a manner that car headlights shined directly into the audience.

For indoor shows, a “dark check” should be performed in which total darkness is attempted. Be sure to give your eyes ten minutes to adjust to the dark, and then identify and eliminate all sources of possible illumination.

Getting the Power Right
The power required to produce an effective beam display is directly related to the size of the venue, the ability to fog the venue, the ambient light level, and the viewing angle. If the last three factors can be optimized, you can get by with a lower powered, less expensive laser. If you are unsure about any of these factors, however, get the largest laser that your budget will allow.

Now that you’ve got a venue which is properly set up for atmospheric effects, what kind of laser magic can you do? The simplest effect is the straight beam, in which a static beam emanates from the projector. The beam can target single or multiple mirrors to create a sequence of patterns.

Straight beams can also target remote devices that add interest to the show. One of these devices is called a reflective diffraction grating. It reflects a beam like a mirror while also breaking up the single beam into multiple shafts of light. The grating also acts like a prism and spreads apart the colors of the output beams. One of the more popular effects is the Machida grating, which projects a 180-degree fan of beams from just one point.

Other, more complex remote devices that straight beams can target are motorized effects. For example, a simple mirror placed on a rotating shaft produces beams that sweep through the air over and over again. This concept has generated a product called a mirror barrel that many companies use as a standard part of their show.

By positioning the laser beam using standard laser show graphic X/Y scanners, we can place the beam under artistic computer control. These effects are called scanned atmospheric effects.

The simplest of these effects is to sweep the laser beam back and forth creating a thin sheet of light. Under the right conditions, simply blowing smoke through a sheet of light will create a moving cloud effect that audiences love to watch. Taking the sheet of light and moving it up and down adds a whole new dimension to explore. Changing colors adds depth and interest to any of these atmospheric effects, especially indoors under low ambient light levels. The effects compound in complexity from here.

Adequate coverage of the entire audience is important if you want everyone to feel the laser display close up. Sometimes the shape of the venue will require multiple projectors so that everyone experiences the show at the optimum viewing angle. In many cases, this can be achieved by using fiber optics to feed remote scanners far from the main laser.

Audience Scanning
The ultimate in beautiful, intense, laser atmospheric effects is created by using the above techniques to actually reach out and touch the audience with laser light. This is called audience scanning. There is a danger inherent here: the light from a laser beam can be strong enough to damage the eye. But if the laser beam is moved rapidly enough through the air, it’s power can be spread over a sufficiently large area to eliminate the eye danger.

In the United States, however, government regulations generally do not allow audience scanning. In the U.S., laser beams can be no closer to an audience than three meters above the floor. In other countries, such as Germany, companies use audience scanning effects in conjunction with light sensors and fail-safe scanning interlocks that shut off the beam immediately if a safety hazard is detected.

As technology advances, and our understanding of eye/color/laser power factors increases, perhaps we will see government-approved audience scanning become a part of shows in the U.S. In the meantime, we Americans can always enjoy the beauty of pure laser beams creating atmospheric beam patterns overhead. There is nothing else like it!

Tim Walsh is president of Laser Spectacles, Inc., and currently serves as Chair of the ILDA Awards Committee.

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Laser Images, Inc.,
Laserland GmbH,
Laser Systems Europe