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Never look into the beam of any laser. OK, there might
be exceptions if you are *absolutely* sure the beam has been attenuated
or diverged enough to be totally eye-safe. For example, the beam from
the optical pickup in a DVD player is safe to view from an oblique angle
at a distance of at least 6 inches since it is highly divergent; the
beam from a supermarket barcode scanner is safe because it is scanning
rapidly; and the beam from a laser rangefinder operating at 1.5 um
may be eye-safe if low enough power density because it won't
penetrate the cornia and lens of the eye.) Distance alone isn't a
guarantee - some lasers maintain a tightly collimated beams for 100s of
feet or more. IR lasers may be invisible but can still cause instant
damage to vision and are even more dangerous than visible laser because
your blink and aversion reflexes don't work if you can't see the beam.
Specular reflections (from shiny surfaces like glass and metal) may be
just as dangerous as the raw beam. Viewing the reflection from a diffuse
surface like a white card is much safer though for higher power lasers,
even if the card doesn't burst into flames, the reflection may still be
unbearably bright.
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Wearing a set of proper laser safety goggles is a good
idea when working with any laser but especially for those rated Class
IIIb or higher. Each type of laser requires its own specific protection
depending on wavelength and power/energy. Just because you have a piece
of colored glass or dark visor from a welding outfit doesn't mean it
will protect you from a laser beam! Using eye-wear can even be important
if you are working on a totally eye-safe laser. Why? Because developing
proper habits will mean that you are automatically protected should you
acquire a much higher power laser - assuming you use the correct
eye-wear!
(Portions from: Lynn Strickland (stricks760@earthlink.net).)
In addition to laser equipment and laser safety gear
manufacturers, large laser surplus outfits often have some minimal
selection of laser safety goggles, but those that are available will
probably cover the types of lasers you are using. However, they may not
have all the regulatory approvals - that's one of the things that boost
prices! :) Also be careful whether the eye wear is designed for diffuse
viewing only, or will withstand a direct hit from the laser. Know what
you are getting - the worst thing is to think you are protected when you
are not. Or, to become so disgusted with the reduction in visual acuity
and clear view resulting from poorly made or mismatched goggles that you
end up not using them at all!
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Be aware of the wavelength(s) power of your laser(s). A
100 W CO2 laser and 100 mW Ar ion laser are quite different and require
different sets of precautions but one is not necessarily more dangerous
than the other. Specific laser classifications and precautions depend on
both wavelength and power.
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Always terminate the laser beam with a light absorbing
material or diffuse screen. Don't just let it fly wildly around the room
to end up who-knows-where.
When adjusting or aligning a laser with the covers off,
beware of reflections from all optics surfaces. Those inside the laser
cavity will have optical power densities much higher than that of the
output beam making even a small percentage of reflection significant.
For example, an argon ion laser outputting a few hundred mW can have 10
or 20 mW reflected from each Brewster window in two directions. These
may be non-existent or weak when you start out but can appear suddenly
as adjusting screws are turned. The risks are even more significant with
a laser producing an invisible beam. Where possible, put sleeves around
the Brewster windows and block reflections from other optics while the
laser's innards are exposed.
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Clearly mark the path of the beam and provide barriers
to prevent accidental contact with eyes (all lasers) and other body
parts (high power lasers).
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Follow all relevant electrical safety regulations with respect to
wire sizes, equipment grounding, and proper hookup, as well as providing
essential fuses, circuit breakers, GFCIs, and other protection devices.
Insulate or block access to all AC line connected and/or high voltage
terminals.
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Provide a 'kill' switch in an accessible location away from the
laser and its beam path just in case you need to cut power in a hurry.
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Put appropriate laser safety and electrical safety warning/danger
stickers near the laser emission aperture and other beam path locations,
on the laser, and on power supply components.
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Never randomly aim a laser out the window. In fact, your laser lab
or workshop should have shades or blinds over all windows to prevent
this from happening by accident. Someone across the street may
inadvertently look into the beam. And, deliberately directing a laser
toward an aircraft is not only incredibly stupid but also highly illegal
- pilots take their eyesight quite seriously! There may be specific
applications or experiments that depend on using lasers outside
(professional laser light shows, line-of-site laser communications,
surveying, LIDAR, etc.) but each will have its additional specific
safety precautions and regulations.
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Instruct anyone else with you as to the hazards of laser light and
make sure they understand all of these guidelines. Those with you may
actually be in MORE danger because they will be looking toward the
direction of the action while you will know what to expect and avoid.
