Study: Many laser pointers exceed approved power, are eyesight hazard

2013-03-26T00:00:00Z Study: Many laser pointers exceed approved power, are eyesight hazardJason Bittel Slate Arizona Daily Star
March 26, 2013 12:00 am  • 

For all the whining everyone's always doing about jet packs and other technology of the future, you'd think we'd be more impressed with the teeming abundance and affordability of lasers.

In fact, we're so over Light Amplification by Stimulated Emission of Radiation, we've relegated the technology to kitschy beach-shop key chains and board games for nerds.

And yet a new study shows a majority of the dinky laser pointers on the market exceed the power level limits set by the Code of Federal Regulations, which means a whole lot of people out there wield far more retina-burning power than they should.

That laser pointers are potentially dangerous shouldn't come as any big surprise. People have been known to point electromagnetic radiation at the eyes of rival soccer clubs or helicopter and airplane pilots.

"The human eye is a fantastic optical instrument capable of concentrating light 100,000 times onto the retina," said Joshua Hadler, physicist and laser safety officer for the National Institute of Standards and Technology Laser Radiometry Project.

"More than a few milliwatts at the cornea can be focused to a spot so small that the power density on the retina can become greater than that generated when staring into the sun."

Power limits put in place by the federal code cap laser pointers at 5 milliwatts. Anything more powerful than that is technically not a "laser pointer" - that is, a handheld laser intended to trick an audience into thinking your PowerPoint slides are even vaguely interesting.

Which is why it's concerning that Hadler and his co-authors Marla Dowell and Edna Tobares found some of the laser pointers they tested to be well above the 5 milliwatt output advertised on the labels. One showoff laser pointer clocked in at 66.5 milliwatts.

Lasers of this magnitude can potentially cause irreparable damage to the human eye. When focused on the retina, they yield more power density than looking at a welding arc.

What's more, green laser pointers in particular fire off a considerable amount of infrared signal in addition to visible light. The human eye is far less sensitive to infrared, which means it can't protect itself by automatically closing like it does with bright, visible lights. Even though you can't "see" it, infrared can still mess you up.

"The damage mechanism that occurs is thermal," Hadler says. "The tissue can't dissipate the heat fast enough, and it burns."

In order to prevent accidental eye scorching, Hadler developed a relatively cheap, easily replicable test bed. He hopes other institutions from universities to corporations will build their own test beds to make sure their lasers are within the appropriate safety thresholds.

The national institute's study shows only 26 percent of the laser pointers tested met industry standards.

That means you'd do well to avoid drawing the ire of that weird little cousin - you know the one - especially if his cat-torturing device is green. A whopping 90 percent of green laser pointers in the study were not in compliance with the federal regulations, compared with 44 percent of the reds.

"Twenty years ago, the technology required to generate this particular wavelength of laser light was a $30,000 piece of equipment that lived in a laboratory," Hadler said. "And now for $10 you can put one in your pocket."

"The damage mechanism that occurs is thermal. The tissue can't dissipate the heat fast enough, and it burns."

Joshua Hadler, physicist and laser safety officer for the National Institute of Standards and Technology Laser Radiometry Project

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