Types of Laser Beams
Developed in the early 1960s, the laser has proved to be indispensable in many areas of research, engineering and commerce. Many kinds of lasers have been developed since then, spanning a power range from less than a milliwatt (mW) to more than one petawatt (PW). Though a five-milliwatt laser's total power is a tiny fraction of a typical light bulb's, the high concentration of its light makes it hazardous. Safety researchers have developed a system for classifying lasers according to their power and potential harm to human eyesight.
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Class I
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These lasers are low-powered and completely enclosed. Since no light escapes the working unit, they're considered completely safe. Lasers in video and CD players and printers fall into this category.
Class II
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Class II lasers are very low-power but not enclosed. Pocket laser pointers are in this class. Their power is less than 1 mW. Your blink reflex is enough to protect your vision from this. If you keep your eyes open, it's possible you might suffer some sight impairment. These lasers, and those with higher power, carry warning labels.
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Class IIIa
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Lasers having power ranging from 1 mW to just under 5 mW fall into this class. The power is greater in this class, as is the potential for eye damage. Some demonstration and laboratory lasers are in this range; training and careful use is a must.
Class IIIb
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The power of these lasers runs from 5 to 500 mW. You can burn holes in paper at the high end of this range. They must be used with carefully designed, light-shielding apparatus and special goggles. Eye damage can result from direct exposure and reflections. Many research lasers fall into this category, though some printers have lasers this strong. In a printer, a safety interlock keeps the laser off if the printer's open. Lasers in this class must have red warning stickers and are subject to state licensing.
Class IV
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This covers all lasers over 500 mW. They have uses in industry, medicine, the sciences and the military. As lasers in this range can be powerful enough to burn through steel, a variety of precautions must be taken in their use. They are regulated by the FDA, OSHA and other state and federal agencies.
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References
- Photo Credit dmuth, creativecommons.org
