Lasers in Entertainment
Scientists have found many tasks and uses for lasers. These devices regularly measure, cut, drill, weld, read, write, send messages, solve crimes, carry telephone conversations, burn plaque out of arteries, and perform delicate eye operations. Over and over again the laser has proved to be an extremely practical tool.
Yet lasers have also proved their usefulness in non-practical applications, especially in the realm of art and entertainment. First and foremost a laser beam is a wand of light; and light itself can be beautiful as well as practical. The sight of a deep red sunset or multicolored rainbow often inspires feelings of happiness, romance, and even awe. For centuries artists have tried to reproduce light's beauty in paintings, and inventors have given artists mechanical tools such as the camera, which uses light to create art that is entertaining (as in the motion picture) as well as beautiful. Because the laser produces a special kind of light, early in the laser era people realized its potential to create special kinds of art and entertainment. And today, lasers are involved in almost all aspects of these fields, from "light shows" to c ompact d iscs (CDs) and d igital v ideo d iscs (DVDs), to special effects in the movies.
Spectacular Combinations of Light and Music
Back in the 1960s when lasers were still relatively new, artists began to use them to produce "light paintings." These took the form of one-time performances in which an artist flashed laser beams in various ways to create visually striking patterns. The beams might be bounced off mirrors placed in preplanned positions or attached to the artist, who would move about, reflecting the rays against walls, glass objects, or into tanks
Unfortunately, not many artists could afford the equipment necessary for light paintings. So it became more common for organizations to stage and charge admission fees to see such displays in public performances, which came to be called light shows. The first recorded public laser show took place at Mills College in Oakland, California, on May 9, 1969. Large fairs and celebrations also began to present displays of laser art. The same group that created the Mills College show put on a much more spectacular version in 1970 at the Pepsi-Cola Pavilion at Expo '70 in Osaka, Japan. More than 2 million people attended.
At the Expo '70 show the laser artists set up rotating mirrors and wired them to equipment that played music. They aimed four colored laser beams—red, yellow, green, and blue—at the mirrors. When the music played, the sounds traveled through the wires and caused the mirrors to spin at different speeds; and the mirrors bounced the beams around the room in complex patterns, sometimes to the beat of the music. Many of the spectators reported that the combination of light and music was breathtakingly beautiful.
A much more spectacular display of laser art occurred during the U.S. bicentennial celebration staged at the Washington Monument in 1976. An audience of 4 million people watched the show up close, and the beams could be seen twenty miles away. Other laser artists staged two such large-scale presentations in 1980, one to help celebrate the city of Boston's 350th birthday, the other to enliven a huge party in honor of President Ronald Reagan's inauguration.
In these major laser shows the light beams could be considered the main attraction; the music supported the visual display. But it soon became clear to people in the music business that the reverse could work just as well. Thus it became common to witness laser shows at music concerts, especially rock concerts. In such cases the music performance is the main attraction, while the laser light show takes on the supporting role. Many well-known rock groups and other recording artists have staged these light shows at their concerts; The Who was the first group to do so and Pink Floyd became particularly famous for its laser shows.
From time to time there have been some questions about safety during rock concert laser shows. Some of the early displays allowed the beams to shine into the audience, which was potentially dangerous; the beams are not powerful enough to burn a person's skin, but if a beam shines directly into someone's eye a permanent blind spot can form. Because of this danger a number of countries have established strict rules about how lasers can be used in concerts.
Laser Discs Create a Revolution
While the laser continues to thrill people in large visual shows, it also entertains them on a small scale in their homes. In the late 1970s and early 1980s a revolution in viewing and listening technology began. First came the videodisc player, which plays movies and other shows on a television screen. The disc was encoded with the visual information (the movie) in roughly the same way that computer storage discs are encoded. A laser beam burns patterns into a film that covers the disc and later a small laser inside the player scans the disc and relays the picture to the screen. The picture produced by a videodisc is brighter and sharper than the one produced by a videotape.
Unfortunately, the first videodisc players that came on the market had many problems. A great many had not been built well, and buyers returned them; also, the companies that built them did not make and supply a wide enough variety of movie titles to satisfy customers. Many more titles existed on videotape, and tape players themselves seemed more reliable; so laser videodiscs did not immediately catch on with consumers.
As experts worked to eliminate the bugs from videodisc technology, laser audio discs, which came to be called compact discs, or CDs, hit the market. These did catch on quickly with the public and rapidly replaced traditional long-playing records. One reason for the success of the CD is its excellent sound reproduction. In a phonograph a needle comes in direct contact with the carved grooves on the surface of the record, and the more the record is played the more the grooves wear down. In addition, they can hold only a certain amount of musical information.
The CD Player
One side of a compact disc has a reflective coating in which a pattern of pits has been etched. As shown in the enlargement below, a laser beam reflects off these pits onto a light-sensitive transmitter. The transmitter converts the pattern of reflections to electronic signals, which are converted to sound.
In a CD player, by contrast—either audio or video—only a beam of laser light touches the surface of the disc. Barring accidents or misuse, therefore, the discs do not wear out. Moreover, they carry much more information than records and the sound is sharper and more realistic. The other reasons for the success of audio CDs are the same as for the early success of videotapes over videodiscs. The audio CD players proved to be largely reliable, few customers returned them, and manufacturers quickly made tens of thousands of titles available. In fact, many titles appeared on discs that could not be found on traditional records.
The Videodisc Comeback and DVDs
Meanwhile, videodisc technology, which had been down but not out, made a comeback. By the early 1990s researchers had considerably improved the technology and produced far more reliable players with disc-produced pictures sharper and more realistic than ever. Furthermore, in an effort to attract new customers, manufacturers offered a wider range of titles and also introduced the concept of deluxe editions of movies. The deluxe versions, which have become almost standard today, often include restored footage (scenes that appeared in the original film but got lost over the years) as well as behind-the-scenes footage of the making of the film, and even outtakes (bloopers).
Later in the 1990s a newer, even more improved version of the laser videodisc—the d igital v ideo d isc, or DVD—appeared. The DVD produces a sharper, more defined picture than either a standard videotape or a laser CD. This is because a videotape picture breaks down into 210 individual horizontal lines, while a CD picture has 425 lines and a DVD picture 540 lines; the more lines, the sharper the image. Expert Rich D'Ambrise explains other superior qualities of DVD:
DVD discs make CDs look like the 5¼ inch floppy [computer] discs of earlier times. Just a single-sided, single-layer DVD disc offers 4.7 GB [gigabytes, each gigabyte equal to 1,000 megabytes, or MBs] of capacity, which is worlds away from a CD's 680 MB capacity. When we start discussing the 17 GB capacity of a double-sided, dual-layer DVD, it's like comparing the scribbles of a one-year-old toddler to a Monet masterpiece. What makes DVD superior to its CD counterpart is the manufacturing process and internal design. . . . Two injection molds are required to make one DVD, which consists of two banded 0.6 mm discs [as opposed to one in a CD]. 8
DVD laser technology had become immensely popular in an extremely short time span. By the close of 2001 an estimated 22 million DVD players had been sold; in that same year the film Shrek sold a record 2.5 million DVDs, soon surpassed by How the Grinch Stole Christmas with sales of 3 million.
The Advent of Holographic Images
Another form of laser light–produced art and entertainment is called holography, a special type of photography that creates three-dimensional pictures. By contrast, a standard camera produces pictures that are only two-dimensional. Holography began to develop in the late 1940s, quite a while before lasers appeared. The basic idea was to shine two separate beams of light at a sensitive sheet of photographic film. One beam would bounce off the object being photographed while the other would travel a different path, and both beams would reach the sheet of film at the same time. Once exposed by the light, the film itself became the hologram. Later, when a person shined a third beam at the hologram, a three-dimensional picture of the object was supposed to be visible.
The idea made sense in theory, but it was very difficult to construct a working model. One problem was that the light in the beams had to be coherent, moving along with all the waves in step. Another problem was that both beams had to be monochromatic. Producing two identical beams with these properties was an almost impossible task at that time. Researchers tried all kinds of light sources, but none worked very well and progress in holography was slow all through the 1950s.
Then, in 1960 Theodore Maiman built his ruby laser and holography received a sudden boost. Researchers now had a light source that was bright, coherent, and monochromatic. They found that they could produce two identical laser beams by passing a single laser beam through a device called a beam splitter. These beams bounced off a series of mirrors to reach the photographic film.
Holograms are photographs that look three dimensional. Objects in a hologram appear to move when viewed from different angles. A hologram is made by directing a laser beam at the object to be photographed. Between the laser and the object, however, is a half-silvered mirror, or beam splitter, which splits the laser beam in two. One of the beams, called the reference beam, is reflected directly from the mirror to the photographic plate. The other, the object beam, first passes through the mirror. Then it reflects off the object and onto the photographic plate. The interference between these two beams when they meet on the photographic plate causes the three-dimensional effect of the hologram.
Almost everyone has seen a hologram at one time or another. The three-dimensional images on credit cards are holograms, as are the many three-dimensional characters and objects portrayed in arcade video games. Sometimes these images seem so real that the spectator invariably reaches out to touch them, only to be reminded that they are illusions.
Some technical problems with holography remain. Objects that are too big cannot be photographed very well. And because monochromatic light must be used, the images produced are in one color. The only way to make multicolored pictures is by combining several different-colored laser beams, which is very difficult to do. The images made this way do not look completely natural. Also, air molecules absorb some of the light and cause the pictures to look grainy. But scientists are working to overcome these problems.
Artists have tried working with holograms but, as with lasers, the equipment is expensive. So holographic art is not yet widespread. A more practical art-related use for holography is in examining ancient
Laser Movie Magic
Still another use for lasers in the entertainment field is the production of special effects for movies. Several companies that produce these effects (usually referred to as "special effects houses") use lasers in highly technical ways to help make their equipment produce truer colors. The first movie to use a laser to print images directly onto the film was Young Sherlock Holmes, released in 1985. Industrial Light and Magic (ILM), perhaps the most famous special effects house, created the effects for the film. In one scene a painted knight on a stained glass church window comes to life. The knight jumps down from the window and chases a priest out of church.
The effect was created in the following way: ILM artists painted the knight onto a TV screen using a special pen that used electricity instead of ink or paint. The image was then stored in a computer that was hooked up to the screen. Next, the artists programmed the computer to rearrange the image so it could be seen from several different angles. Then the computer created pictures of each of the different movements the knight would make in the finished scene. When the artists ordered the computer to play back all these images quickly, the knight appeared to move around on the computer screen.
In the last and most important step the artists transferred the computer images of the knight onto the photographic film. In creating similar effects for previous movies this was done by simply photographing the images directly from the computer screen. But the picture on a computer screen is not as sharp and bright as film-makers would like, so the ILM artists decided to connect the computer to a laser. The computer directed the laser to transfer, or "paint," the stored images of the knight right onto the blank film. The knight now showed more detail, and the colors were much more vivid. Later, this film clip of the moving knight was combined with separate film footage of the priest in the church. In the final version that appeared on theater screens the knight seemed to be actually walking around inside the church.
Many later movies have employed this and other laser techniques. The blockbuster Jurassic Park 3, for example, used a laser to create computerized models of the dinosaurs that run amok in the film. First, technicians made a small clay model (called a maquette) of a dinosaur; then they ran a laser beam across the maquette's surface, and the beam transferred highly detailed images of it into a computer. Later, animators used highly sophisticated computer animation programs to make the computer images come to life.
These examples illustrate the use of lasers behind the scenes. But what about lasers on screen ? As strange as it might sound, when moviemakers want to portray an actual laser beam on the screen, they cannot use a real laser. For instance, contrary to popular opinion the laser swords used by Luke Skywalker and other characters in the Star Wars films were not lasers at all.
There are a number of reasons why such on-screen laser beams have to be faked. First, real laser devices would not produce beams only three feet long; instead, the beams would keep on going and punch holes in the furniture, walls, and bodies of innocent onlookers. Also, the effect of the two beams smashing together like regular metal swords is completely imaginary. Real laser beams would just pass right through each other, an image that would make a movie fight appear disconcerting and more comical than dramatic. The most obvious problem with using real lasers (if such handheld versions could even be built) would be the danger posed by the brightness of the beams. The actors and most of the members of the film crew would all be blind within an hour. For the moment, therefore, the depiction of laser beams on film must be accomplished though more traditional kinds of special effects.
Science Fiction Lasers Perpetuate Misconceptions
Science fiction movies not only utilize lasers in creating their special effects but also regularly depict lasers or laserlike devices. Unfortunately these portrayals of laser light are often inaccurate for the sake of dramatic effect; and this perpetuates several common misconceptions about lasers, as pointed out here by J.P. Talbot in his article "Lasers in the Movies Reality Check: Science vs. Science Fiction."
Let's speculate on what would actually happen if you were a member of a large fleet of friendly ships engaging enemy ships in a laser beam battle in space. . . . Science Fiction: You fire a laser weapon at the enemy and you "see" and "hear" the beam emerging from your laser gunports (which violently recoil) and watch the "beam" travel very fast toward the enemy ship, which promptly bursts into flames and explodes very loudly (a sound that you hear instantaneously). Science Fact: You quietly fire an invisible beam from a laser weapon without recoil. . . . Your laser beam travels at the speed of light [so you could not watch it travel]. . . . Sound doesn't travel through a vacuum [so you would hear neither the laser discharge nor the explosion]. . . . Most space ships don't "burst" into flames since there's no air in space to sustain such explosive combustion.
Still, real lasers have added a fresh, visually exciting dimension to the world of entertainment. In the years to come it is certain that scientists and artists will continue to combine their talents to produce many inventive and dramatic new forms of laser-based entertainment.