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Show
Basics: Laser Graphics |
Small
Beam of Light
Leads to Dazzling Images
By
Ivan Dryer, Laser Images
http://www.laserimages.com
Animated Neon! That's
an approximate description of laser scanning: the richly colored
line-drawing quality of a neon sign set in motion with equal
contrast and even greater color saturation. It's a medium that
makes any message special. Laser scanners can project names,
logos and animated imagery onto almost any surface-including
the side of a mountain, the curved dome of a planetarium, even
a sheet of pulsating water. Just about everybody would like to
see their name in lights-especially laser lights. What's involved?
A laser produces a tiny linear beam of intense light that appears
as a small dot when it strikes a surface. To make it move you
have to "scan" it by wiggling one or more mirrored
surfaces. Once the dot of light moves fast enough, a phenomenon
called persistence of vision causes your eye to perceive the
movements of the dot as solid lines of light.
In
the Beginning
Early laser hobbyists mounted mirrors on speaker cones to create
wildly gyrating ribbons of laser light that literally danced
to the music.
Then, small mirrors mounted on rotating shafts (galvanometers)
were used to create repeatable excursions (back and-forth motions)
that scan a "line" of light. The line was called an
"x axis." And by bouncing that x-axis line off another
galvanometer mirror moving in a different direction (the y-axis),
circles and more complex shapes called Lissajous figures could
be generated. And thus was x-y scanning born.
Over the years, since the first galvo scanning was done in the
1960's, galvo's have gotten faster, wider in scan angle, and
have added position feedback to cause them to stop very nearly
at the same point at the end of each excursion. This made x-y
scanning far more accurate. And it allowed line drawings of simple
representational images such as faces and words to be made.
The introduction of a third scanner, or a rapidly-pulsed crystal
called an acousto-optic modulator, allowed images to be "blanked"
so that unwanted connecting lines could be omitted and so that
dimming and brightening of the image could impart a sense of
depth, or 3D. This vastly improved the ability to create more
complex images with a single x-y scan set, including wireframe
3D renderings very much like CAD designs.
Full-Color
Scanning
Most recently, the polychromatic acousto-optic modulator (PCAOM)
was introduced to make full-color RGB (for red/green/blue) scanning
simple and effective. Now, it's possible to assign different
colors to different parts of the image with full control of the
color assignment during animation.
So how is laser animation or a laser graphic (a word, corporate
logo, or other static image) made? It's done by connecting the
dots in much the same way children's coloring books do. The points
are entered into a computer operating with special laser graphic
software. The primary limitation on the complexity of the scanned
image mirrors is the low kilohertz range in which most of today's
x-y scanners operate .
The speed and accuracy of the scanner--and the software driving
it--determine how many points can be accurately hit without overshooting,
or "ringing." The process of entering and editing the
points is called digitizing, and a good digitizer learns the
scanner characteristics well enough to know how to place the
minimum number of points in just the right places to create the
most complex graphic frames possible.
If the frame is part of an animation sequence-such as a player
throwing a ball--a sequencing program is employed to put each
frame in its proper place in the action sequence.
But what if the x-y scanners simply can't move fast and accurately
enough to generate the image you must have? Complexity can be
readily, if not inexpensively, increased by adding one or more
additional channels--in other words, more x-y scanners with blanking
systems such as PCAOM's. These scanner sets are registered together,
and the labor of creating the complex graphics or animation is
divided between them.
It's also possible to project three-dimensional scanned images.
The most common technique for achieving this requires viewers
to wear polarized eyewear and a laser projector that can simultaneously
project two versions of the same image polarized along different
axes. Specially polarized glasses separate the images so each
eye sees a different view of the same image-the result can be
stunning stereoscopic laser imagery.
Planning
Your Show
When you've decided you want to see your name in laser light,
how do you decide what you need as a light source? To answer
those questions, even more have to be asked, such as: What color
or colors are required? Can it be monochrome? What is the audience
size? Who will create and operate the scanned display? Are the
necessary utilities (power, water) at the site? Does a screen
have to be brought in and rigged?
The answers to these questions are often best left to professional
laser companies that specialize in creating and displaying scanned
graphics. Given the size of the audience and the effects wanted,
it's a fairly straightforward process to determine the laser
power required and how much scanning hardware will be needed
to create the desired imagery. The scanned images can be supplemented
with aerial laser beams and pyrotechnic effects, all synchronized
to the same musical soundtrack.
Cost
Factors
So what will it cost? That, of course, has a lot to do with how
big your image is and how complex and colorful the animation
must be. The laser power, color requirements (a red-only Helium-Neon
laser is relatively inexpensive) and image complexity/duration
are the keys to cost. A static logo from an EPROM chip, projected
on a small screen indoors can be quite low in cost. The next
step up would be low- or medium-power full-color projector suitable
for indoor and small-scale outdoor installations.
At the high-end of the scale, say for an outdoor audience of
1,000 people, you may require a high-powered, water-cooled laser
system that can cost several thousand US dollars to rent for
an evening (of course, additional nights are substantially less
expensive).
Although a custom-designed laser graphics sequence is far less
costly to produce than computer-designed video animation, it
can still cost several thousand dollars per minute for original,
top-quality laser animation work. Costs can be kept down by using
stock animation images and by reducing the complexity of the
original artwork.
When showtime comes around, you turn on the laser, press the
play button on the digital tape deck that stores the music and
image data for your show, and mesmerize a big crowd that gives
you a standing ovation. Best of all, your client or product has
been well served by a tiny beam of dazzling laser light that
creates images that make film, video and slides look pale in
comparison. The best laser graphics are big, bright, colorful
and sophisticated. When you need to make a statement and get
attention, nothing else will match a laser.
Ivan Dryer,
president of Laser Images, is a past president of ILDA and recipient
of the association's Career Achievement Award.
Additional
Show Basics Links:
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Images from top:
Laser Images, Inc.,
Laserland GmbH,
Laser Systems Europe
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