LASER EXPERIMENTS OF SKB "PROMETEI"

Once a new technology is assimilated by art - after extensive trial and error - a specific sphere of use results in which its potential is presented in its optimal, organic form. For example, the artistic form corresponding to light emanating from the optical quantum generator (OQG) is the laser programme - an audio-visual, light-musical performance usually held under an artificial sky in a "laserium," similar to a planetarium [1,2]. The laser has also been used in both dramatic and musical theatre [3], where its unusual properties are usually used only as a "spicy condiment" accompanying a traditional light palate. The exoticism of the laser is most fully exploited in the eclectic discotheque environment.

The laserium is based on maximal use of the possibilities of OQG emanation. SKB "Prometei", the artists' group of which I am the director, established contact long ago with Ivan Dryer, an American light-musician and laserium pioneer. My group has many videotapes of laser programmes produced by Dryer and by his colleagues in different countries, including those at a laserium in Budapest, Hungary, which I had the opportunity of visiting. On the basis of my acquaintance and experience with this topic, I would like to make the following statements.

There are three main methods of using laser light for artistic purposes (with the exception of holography): (1) the projection of laser beams into space, (2) the creation of interference pictures on flat surfaces and (3) the creation of contour graphic images through the high-speed scanning of a screen with a laser beam.

The first method, resulting in laser-beam projection into space, relies on the perception of high-power laser beams in air filled with dust or smoke. Using mirrors (static or dynamic) to create multiple reflections of the extremely thin rays, one can build a kind of dynamic light architecture through transformations of incorporeal beam constructions - such as a "web," "fan," "light curtain," "cone," "arrow" or "bed-curtain" - made possible through the use of rotating double-sided mirrors, reflecting balls, cylindrical prisms, pyramids, bevelled rotating reflectors with changing angles, etc. As a rule, the creation of images from beams is performed through periodic interruptions of the beam, i.e. in conjunction with a strobe effect, which can be spectacular in itself. Without a strobe effect, images similar to the fan are made through the use of diffraction gratings, which split one ray into several. These gratings can have different features and properties that are combined in various ways. A critical component of these beam systems is a high-speed commutator with a set of revolving semitransparent and reflective mirrors, which allow the optimal and variable use of light from one laser beam [4]. It is common practice to use the "light architecture" of a laser beam in conjunction with the physical architecture of a space to achieve a desired effect; this method is used not only in the interior of concert halls (i.e. planetariums and theatres) but also under the open sky.

Fig. 1. Revolving head for laser projector, with rotating cassettes. (Designer: Kamil Gimazutdinov). Inside every cassette are formbuilding transparent discs. There can be two such discs that rotate on one axis in different directions. Diffraction gratings can be mounted in place of one of the form-building discs.

The second method, resulting in interference patterns on flat surfaces, is based on the use of accidental phase modulation, which occurs when a laser beam passing through optically heterogeneous media is refracted at different points and angles along its way, resulting in interference patterns projected on a screen that change in contour and texture with each change in media. The media can be made of solid transparent matter (e.g. moving plates of nonuniform structure - usually round discs mounted in a revolving cassette) [5]. If a set of cassettes is loaded in a revolving head (Fig. 1), one can exclude the element of "chance" by experimenting with the selection of visual effects. Sometimes an additional objective lens is used to concentrate the light field. Sometimes traditional projection objective lenses (transfocators) are mounted at the beam's point of exit. These form-building methods can be used in the same cassettes (to increase image possibilities) with diffraction gratings (Fig. 2), curvilinear reflectors or a large moving lens (for the deformation of light images).

Fig. 2. Result of diffraction grating action on the interference image.

As mentioned earlier, one can project a beam through solid, transparent plates; it is also possible to project a beam through thin layers of flowing liquid or through gases or steam. Let us look at the latter method, as tested by SKB "Prometei" [6]. Figure 3a shows a laser beam reflected from a metallic, mirrored surface layered over a lavsan pellicle (a thin, transparent, reflective film) and thinly coated with a reflective substance such as glycerine. When the beam is projected onto the mirrored film, the pellicle will start to sag due to the heat and, acting as a reflecting lens, it will stretch out and wash away the beam (Fig. 3b). In this way, a contoured image with a fibrous structure is formed on a screen. If the laser has enough power (1 or more W), the lavsan will begin to steam, and the reflected beam will pass through the streaming vapors. This streaming - or the optical heterogeneities of a gas brought to a great heat - can create the complex visual effects of fountains or explosions within the initial image. If the pellicle is not moveable, the beam will eventually burn through it (Fig. 3c). Therefore, the pellicle must be moved slowly or rotated before the beam; the image and its textural composition will then also transform smoothly into fantastic pictures that resemble revolving galaxies, space clouds and so on (Fig. 4a,b). The effect of the transformation depends on the speed of the pellicle's movement, the physical makeup of the pellicle and the composition of its coating (e.g. colophony, vaseline or glycerine).

Fig. 3. Schematic figure demonstrating laser-light effects enabled by a mirror lavsan pellicle.


`Fig. 4. Light effects resulting from burning lavsan pellicles.`

To facilitate these methods, SKB "Prometei" has designed a light-effect laser projector (Fig. 5). To make the projector, reflecting pellicles were cut in the form of discs and mounted in a revolving cassette. If the cassette rotates slowly, the laser beam will burn through the pellicle. To prevent the beam from becoming useless, we mounted a second disc behind the first one; in case the second disc also burns, we mounted a third disc behind the second. Because the burning pellicle still continues to partially reflect light, three independent light images are possible with one beam. All the cassettes are fixed on a platform that moves forward very slowly. Finally the beam will burn through the last pellicle, creating a spiral that allows maximal use of the pellicle's shape. A variety of light effects on the screen can be made by changing the pellicle's speed of revolution or the cassette platform's speed of forward movement, or by changing the angles of pitch of the cassette. The interference pictures created using the second method are often used as backgrounds onto which laser graphic pictures may be projected (Fig. 6).

Fig. 5. Light-effect laser projector with three discs made from reflecting lavsan pellicle. (Designer: Rustem Saifullin).

Fig. 6. Image resulting from projecting laser graphics onto an interference background.

o create such pictures, the third method, resulting in contour graphic images through scanning a screen with a laser beam, is employed [7,8]. Achieving graphic effects through the use of lasers is analogous to rapidly moving a lit cigarette or a sparkler in dark air in order to produce a momentary image of glowing lines. A laser beam produces a bright, blazing point when immobile; it can produce graphic lines of light when moved across a screen. This is achieved due to beam deviation along the coordinates (x,y). This process can be described as similar to that of the electromechanical oscillograph, except that instead of an electronic ray, a thin laser beam is used [9]. A vector scanner is made either with a pair of small, lightweight mirror reflectors oscillating with a frequency of hundreds of Hz, or with optical deflectors (the scanner's angle is much smaller with this method). The generation of Lissajous figures, as in an ordinary oscillograph, is clearest with this method. One can - with the help of a personal computer - input more complex signals to the scanner and project other contour pictures (abstract or concrete), which can be set into motion through animation methods (Fig. 7). Different kinds of graphic information input tools (e.g. mice and light pens) can be used, but the majority of pictures projected in laseriums are supplied as special programmes that can be shown serially. Necessary components of such units are a brightness modulator and an additional scanner to swing the image around slowly (on any trajectory). Sometimes diffraction gratings (single or double, static or revolving) are also used to multiply an image - for instance, in the production of an ornamental pattern (Fig. 8). The generation of pictures through a video scan of a laser beam (through the use of optical deflectors) is a modification of this method. However, since this method of obtaining an image is not economical, it is not usually used at laseriums.

Fig.7. Animated mouse projected in the experiments of SKB "Prometei" on the facade of a skyscraper at a distance of 750 m.

Fig. 8. Reproduction of graphic image with the help of double diffraction gratings.

The first laseriums opened in the United States after an official premiere on 19 November 1973 (in Los Angeles, San Francisco, Miami, Denver, St. Louis, Seattle, San Diego, New York, Boston and other cities). Next, they opened in Canada (Toronto, 1975), Japan (Kyoto, 1976), England (London, 1977), Hungary (Budapest, 1980) and other countries. In 1980, there was a short-lived attempt to convert a Moscow planetarium into a laserium, but no serial apparatus was produced in the states of the former USSR, in contrast with the United States, where laseriums were designed and produced by dozens of firms [10,11].

Today, SKB "Prometei" produces laserium models and plans for a company in Kazan, Russia, which plans to produce such an apparatus for the Commonwealth of Independent States. Laser units designed by SKB "Prometei" will be used in the spherical hall of a future audio-visual center at the Kazan Conservatoire [12].

LASER EXPERIMENTS OF SKB "PROMETEI"

Bulat M. Galeyev