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Laser
Hobbyists - Hobby FAQ
A page with some of the more Frequently Asked
Questions about hobbyist laser systems. We welcome your submissions
and suggestions for this page.
Q: I want a low
cost laser but I am not sure if I should buy a HeNe or a diode laser?
A: HeNe lasers are usually more
collimated (the beam spreads less) than diode lasers. HeNe lasers are
usually made of glass making them less rugged and they generally require AC
power. Diode lasers are now available in the 5 mW range and are solid state
devices making them more rugged. Theoretically a diode laser will last
forever while the gas in a HeNe will eventually be consumed. Diode lasers
can often be run from battery power making them ideal for portable
applications.
Another option which is a bit more costly, but is much brighter to the eye, is
buying one of the green DPSS laser modules - many of these have a modulation input
allowing the laser to be turned on and off rapidly. This is ideal if
you later plan to do graphics as the modulation input can be used for
blanking.
Q: What does DPSS stand
for?
A: DPSS stands for Diode Pumped
Solid State Laser. In a DPSS laser, an infra red diode laser is used
to pump a crystal that up converts the frequency to 532 nM which is a bright
lime green. The eye is very sensitive to this frequency so that a 5 mW
532 nm laser appears as bright to the eye as a 15 mW HeNe laser. Other
combinations of pump diodes and crystals can be used to
produce red and ble lasers so it is possible to have an
all solid state RGB (full colour) laser.
Q: What is the
most powerful laser I can use without a license?
A: The rules on maximum permissible
power for public displays vary from jurisdiction to jurisdiction. In the
United States the maximum is about 5 mW [contact the CDRH for full details].
Other countries follow the international standards which are approximately 1
mW for 1 second into a 7 mm aperture rule. For the exact details you should
contact the regulatory authorities in your country.
For more information about laser safety in various countries, see the Safety
Regulations page in the Safety
Section.
Q: Can low power
lasers be dangerous?
A: YES. You should observe the same
kinds of safety rules that laser professionals use. NEVER shine a laser in
anyone's eyes. The concentrating effect of the lens in the eye [see Basic
Laser Safety for more info] can cause damage even with a low power
laser. If you turn professional later, you will have good working and safety
habits.
Q: I bought some
GAL2 scanners. Why can't I do graphics with them?
A: The GAL2 scanners and other low
budget scanners do not go fast enough to produce graphics. The speed of
galvos for graphics systems is rated in PPS [Points Per Second] but all
galvos can be speed rated in Hz when using an analogue sine wave as a test
signal. The GAL2 and other low cost scanners usually don't go much faster
then 300 Hz. The slowest scanner you can use for graphics, the G124, has a
speed of 700 Hz while professional closed-loop scanners can attain speeds up
to 7,000 Hz. The much slower consumer oriented galvos lack the speed and
accuracy needed to follow the complex graphics signals. They can still be
used for abstract generation and some beam effects.
Q: Can you use
sound cards from computers to generate scanned effects?
A: You can use a sound card to generate
scan signals if you first modify it to pass DC signals as graphics scanners
require DC to produce images. Warning: this probably voids your warrantee
and may damage your speakers or sound system. You will have to design your
own sound control software to generate the effects.
Q: I have
programming skills and I want to make my own laser graphics system. Is
there any info on software and hardware for making my own graphics system?
A: The design of a laser graphics system
is a complex and time consuming task. The first and most important
part is a hardware interface or display processor to take the computer data
and output it to the scanners. These cards are not readily available
as each laser company designs/builds a hardware interface to suit their
needs and market. There are a few companies that will sell you a card
with the code to drive it. Once you have that, you will need to
program all of the software and design a GUI to make the images and
animations with will take you hundreds of hours.
Laser F/X would like to encourage Linux programmers to work on this kind of
project using the "open source" model but to date, we have not
found any volunteers.
Q: I have seen
those wispy 'gas cloud' effects they use at laser shows, how do they do
that?
A: The effect is called a lumia and is
generated by a lumia wheel. You can build one by using a 1 RPM [or slower]
motor with a disk of bumpy glass or plastic attached. Simply shine the laser
through the disk and watch the results on the wall.
If you use plastic with a very regular pattern such as the pyramid embossed
type found on fluorescent lights, you will get a simple repeating pattern.
If you use glass with a more random bumpy surface such as that found in old
style shower doors, you will get a more interesting irregular pattern. Glass
or plastic that is only waved [the bumps are not large] will spread the beam
less while glass that is very bumpy will spread the laser more making a
larger projected pattern.
The best way to find glass or plastic materials for lumia wheels is to go to
a stained glass or art glass supply house. As them for some small samples to
try out. Once you have found some you like, you can have them cut them into
handy disks. A simple way to make the disks interchangeable is to
epoxy a 25 mm [1 inch] square of 'Velcro' type hook material on the hub and
a matching square of loop onto the wheel. Note that these can come loose
over time from vibrations and your disks may fall off and shatter.
Q: I
have heard people talking about a "Liquid Sky"
effect. What is that?
A: "Liquid Sky" is a
fancy name for a very simple effect. By scanning a flat
sheet (straight line) just above the audience's head, it appears
they are under a "sky" the colour of the laser
beam. Since the beam is almost one dimensions in the
vertical direction, it lights up smoke particles in a cross
section so the swirling of the smoke due to air currents become
readily visible.
Q: Can I build my
own laser?
A: To build your own laser, you would
have to have access to a machine shop, have glassblowing skills, vacuum
equipment and access to rare gasses. I would be like trying to build your
own light bulb or fluorescent tube. It is simpler to purchase a laser and
low cost HeNe and diode lasers are readily available.
For those who would like to build their own laser, we have provided some
resources on the Laser
Construction page.
Q: I need more technical
information about lasers. Where can I look?
A: The Backstage
area of LaserFX.com contains a lot of technical information about laser
light show applications. For more technical information about the
lasers themselves, Sam Goldwasser maintains Sam's Laser FAQ which is filled
with technical details on a variety of lasers - LaserFX.com is pleased to
act as a gateway for Sam's Laser
FAQ
DISCLAIMER:
Some of the information in the Backstage area is provided by the persons or
companies named on the relevant page(s). Laser F/X does NOT endorse or
recommend any products/services and is NOT responsible for the technical
accuracy of the information provided. We provide this information as a
service to laserists using the Backstage area.
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