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Introduction to Laser Safety

Lasers are unique in their safety hazards, particularly to your vision. While the dangers of firearms and explosives are obvious, the possibility that a low power laser can cause severe damage to vision is something that needs to be stressed. For high power lasers, there may be fire and other hazards as well. Take several minutes to read over this page to learn more about laser safety.

Take Care of Your Eyes!

Portable lasers have recently gained popularity with numerous hobbyists, experimenters, entertainers, and serious researchers alike. However, except for very low powered lasers, lasers do pose a hazard particularly to vision. Since the visual receptors lining the eye's retina are part of the central nervous system, they do not regenerate. Therefore, don't take your eyes for granted because once your eyes are damaged, they will not grow back!

There are several reasons that even small lasers can potentially cause damage to vision:

• Laser beams are coherent, nearly parallel, and usually highly collimated. Since the energy is concentrated in a small dot, the lens of the eye will further focus it causing damage to the retina.

• A cheap laser pointer can also produce a highly collimated beam.

• Even at power levels considered relatively safe, you should not deliberately stare into a laser beam for any reason. For these relatively low power lasers, permanent eye damage is not that likely but why take chance? For these lasers, viewing the spot projected on a white surface is perfectly safe.

• Even though light bulbs are measured in Watts, they are unlikely to cause permanent damage to your eyes. This is because the light from the bulb is not focused and collimated.

Laser Classifications:

• Class I lasers - Lasers that are not hazardous for continuous viewing or are designed in such a way that prevent human access to laser radiation. These consist of low power lasers or higher power embedded lasers (i.e., laser printers).

• Class II visible lasers (400 to 700 nm) - Lasers emitting visible light which because of normal human aversion responses, do not normally present a hazard, but would if viewed directly for extended periods of time. This is like many conventional high intensity light sources.

• Class IIa visible lasers (400 to 700 nm) - Lasers emitting visible light not intended for viewing, and under normal operating conditions would not produce a injury to the eye if viewed directly for less than 1,000 seconds (i.e. bar code scanners).

• Class IIIa lasers - Lasers that normally would not cause injury to the eye if viewed momentarily but would present a hazard if viewed using collecting optics (fibre optics loupe or telescope).

• Class IIIb lasers - Lasers that present a eye hazards if viewed directly. Class IIIb lasers do not produce a hazardous diffuse reflection except when viewed at close proximity.

• Class IV lasers - Lasers that present an eye hazard from direct, specular, and diffuse reflections. In addition such, lasers may be fire hazards and produce skin burns.

General Laser Safety Guidelines

• Never look into the beam of any laser. Distance alone isn't a guarantee. Some lasers maintain a tightly collimated beam for hundreds of feet. Specular reflections, reflections from shiny surfaces like glass and metal, may be just as dangerous as the original beam. Viewing the reflection from a diffuse surface like a white card is much safer though for higher powered lasers, the reflection may still be unbearably bright.

• Wearing a set of proper laser safety goggles such as the LaserShades 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. Using LaserShades can even be important if you are working on a totally eye-safe laser. This will help develop proper habits for laser safety.

• Always terminate the laser beam with a light absorbing material or diffuse screen. Don't just let it fly wildly around the room.

• When adjusting or aligning a laser, beware of reflections from optical surfaces.

• Clearly mark the path of the beam and provide barriers to prevent accidental contact with eyes.

• 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.

• Never randomly aim a laser out the window. Someone across the street may inadvertently look into the beam. And, deliberately directing a laser toward an aircraft is a federal offense in the United States! There may be specific applications or experiments that depend on using lasers outside but each will have its additional specific safety precautions and regulations.

• 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.

• If none of these safety procedures can be followed, as with using green laser pointers to identify astronomical objects in the sky, we suggest taking as many precautions as possible. Only use a pointer that has the normal momentary switch so it will go off instantly if dropped and make sure all the observers are aware of the dangers of Class IIIb lasers so they won't do anything stupid.