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Tech Tips for Practicing Laserists
A Quick Tour
of the New Schneider Showlaser
Solid-State RGB Projector
By
Aron Bacs,
Audio Visual Imagineering Inc.
(An extended version of this article in Word format is available
by
clicking here.)
 About 27 years ago when I got
my first laser, I would spend hours looking at the inherent beauty
of the thin red helium-neon beam as it passed down the upstairs
hallway into my bedroom. Not since this first glimpse of laser
light have I been so moved as when I viewed a new source of laser
light almost a year ago. This article hopes to describe my personal
experience with one of the most color rich and newest RGB lasers
on the market today, the solid-state Showlaser from Schneider
Laser Technologies.
As
a design engineer and director of research and development, I
get to play with the coolest new technologies around. Whenever
new technology arrives, it is often an unknown. That is definitely
the case here. Very little technical information has been published
on the Showlaser. I would like to tell you about some of my experiences
with this laser system and what to expect when and if you decide
to use one for yourself.
The Showlaser’s main goal is to produce very high output
power, on par with color-modulated large-frame ion lasers, but
with much less input power—about 20 times less! The system
is rated at 18 watts average internal power from the main RGB
laser crystals, with a minimum of 13 watts of color-balanced
RGB light entering the FC style fiber. We have been getting over
10.5 watts out of the fiber. Electrical input ranges from 220-240VAC
(50/60Hz) at less than 3KW (that’s the power consumption
of two hair dryers). Another plus is the expected lifetime of
the laser crystals: 10,000 hours.
Schneider orginally developed this technology for RGB laser video
projection. The Showlaser uses the same RGB source as the company’s
video unit but is a vector scanning projector designed for laser
light shows.
Although the laser output is pulsed (7ps/80Mhz), the pulses are
too fast to be seen in scanned lines. The 7ps pulses do, however,
reduce the laser “speckle”effect, which is of utmost
importance when lasers are used for video.
The speckle is not completely gone. While most laser speckle
is coarse (like 80 grit sand paper), the Showlaser speckle is
very fine (like 400 or 600 grit). This makes the imagery look
cleaner, because as you view the fine visual details in an image
you are not distracted by the relatively larger speckle.
The Showlaser contains five major systems. These are 1) an RGB
laser, 2) nine diode pump lasers, 3) a system control computer,
4) low-voltage power supplies, and 5) a closed-loop cooling system.
Three
Efficient Wavelengths
The Showlaser produces only three wavelengths: 628nm, 532nm,
and 446nm. Ion lasers, on the other hand, can lase at many different
wavelengths, spreading their optical power over eight or more
lasing lines. Some of these ion lines are undesirable for graphics
systems where high color saturation is needed to portray full
color images properly. The 488nm line often causes a washed out
look, and is frequently omitted or reduced. Unfortunately, the
488nm line is also one of the stronger lasing wavelengths in
Ar+ and/or Ar+/Kr+ ion lasers. When you attenuate or remove this
line, you can lose 25% or more of the laser’s total output
power.
 The Showlaser does not suffer
from any of these afflictions. It is a mix of several newer solid-state
technologies. For example, to generate the green 532nm wavelength,
the Showlaser is similar to other existing diode-pumped solid
state lasers (DPSS). However, to generate the red 628nm and blue
446nm wavelengths, newer technologies are used. These technologies
include second harmonic generators, optical parametric oscillators
and sum frequency mixers.
All the main optical components are mounted on a series of vibration
isolated optics tables within a “dry” nitrogen filled
envelope. A little scary at first from a service point of view,
but since I don’t go messing around inside our sealed DPSS
or ion lasers glass envelopes either, it’s a moot point.
Besides, alignment of the internal beam paths is done by motor
controlled mirrors.
The systems’ first main laser oscillator feeds a series
of optical amplifiers. These amplifiers are needed to increase
the power of the main laser oscillator which is modelocked (~7ps
pulses at ~80Mhz). The main laser oscillator uses high peak power
pulses, on the order of 30KW per pulse, because the nonlinear
crystals (which do the frequency doubling and sum frequency mixing)
operate much more efficiently at higher input powers.
An onboard computer/controller oversees the proper operation
of the laser system, including the start sequence (which takes
about 30 minutes), the temperature control of the nonlinear crystals
and pump diodes (via the on board closed-loop refrigeration system),
and the low-voltage power supplies that provide power for diodes
and sensors. The start sequence time is needed to stabilize the
temperature and currents of all the crystals and associated components,
including the vibration isolated optical tables. I believe as
more data is collected, this time may be shortened.
Because the Showlaser has a computer on board, it is possible
to upload new software/firmware, as well as diagnose the system
should there be a problem. I wish my ion lasers could tell me
how their color balance, power, temperature, alignment, etc.
were doing.
Inside the Showlaser, the RGB beams bounce off a set of computer
controlled mirrors through specially designed high efficiency
acousto-optic modulators, then to another set of computer controlled
mirrors, and then to the fiber input coupler.
Collimated
Output
The output from the Showlaser is an FC style fiber optic connector.
We use the high-quality 25mm fiber cable supplied by Schneider.
Through careful optical design of the collimator and projection
optics, I have projected ILDA 30K images with a spot size of
less than 50mm diameter over a screen distance greater than 100m.
This was achieved at AVI’s Hersheypark installation in Pennsylvania,
and I can say that the output is much better than most direct-fed
ion laser systems!
The Showlaser ships in a reusable shipping container made of
a lightweight, fiber composite material, complete with an unloading
ramp with stainless steel skids. It takes at least two people
to uncrate the unit, mostly due to the size of the container
(approx. 3.5’ W x 5’ L x 4’ H) and weight of the
laser itself (660 lbs). We took great care in rolling the laser
down the container’s ramp to the floor. The laser itself
comes complete with heavy duty casters. Two large handles on
the unit’s ends are convenient lift/handling points. We
take the same care when unpacking our ion lasers as we do with
the Showlaser, but I must say that handling ion lasers is a bit
more precarious. This is due to an ion’s length, weight,
umbilical cable and sheer dead lift required by personnel. Once
on the floor, a single person can move the Showlaser to its final
destination with relative ease.
Computer
Controls
A laptop (or desktop) computer with a parallel and/or a serial
port is needed to access the laser operations (for both control
and diagnostic modes), although there is a control box in the
works that will eliminate the need for a computer. For simply
starting the laser, there is a front panel control that requires
you to merely turn the key to the On position and press the start
button. This can also be done by computer, which is great when
the laser is in a remote location.
Shutting down the laser system is very simple, whether using
software and/or the front panel controls: simply push the stop
button and turn the key to Off.
You can pack up the laser immediately after use, so you get the
30 minute startup time back at the end of the show. Other than
topping off the deionized cooling water and periodic cooling
filter changes, there’s not much maintenance. Again, like
ion lasers, changing the inline water filters is nothing new.
There is much additional detail I would like to go into on the
complete operation of the unit, but I hope I have given a basic
rundown of the system. To use the Showlaser is to appreciate
the engineering effort that was undertaken to make this both
a visually amazing laser system as well as one that’s easy
to operate.
AVI should have at least one system at ILDA 2001 for everyone
to see, enjoy, and ask further questions. Please visit the Laserist
Web site for a longer version of this article and additional
Web references (www.laserist.org/Laserist), or contact me for
more information. See you in November at ILDA 2001!
Aron Bacs, AVI: (+1) 407/859-8166;
aronb@avilasers.com
www.whitelightlaser.com
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