Laser Pointers
Gary E. Myers © 2004
The first laser pointers were small helium-neon (HeNe) gas lasers. They were expensive, fragile, bulky, and had short battery life. In practice, their use was limited. In recent years, all this has changed: laser pointers now are solid-state and resemble slim penlights, most operate on two AAA cells, their battery life is several hours, they are rugged, and many sell for $20 or less. In fact, I recently saw well-made Class 3a keychain laser pointers for sale at the checkout counter of a local store, for $9.99. The convenience, low cost, and "gee-whiz" factor have made them quite popular. They now are common consumer devices, and are purchased by and for teenagers and children, and even pets (one ad says, "Drive your cat crazy!").
In the wake of this proliferation has come a concern about their safety. It is not unusual to see accounts of incidents involving laser pointers in the popular press, and one Chicago suburb has banned the sale of laser pointers to persons under age 18. The FDA has issued a warning. Are these concerns well-founded?
It is a fact that most laser pointers are Class 3a and thus are, at least theoretically, hazardous: momentary intrabeam viewing of a Class 3a laser results in an exposure that exceeds accepted U.S. standards (ANSI, ACGIH). One who is acquainted with laser safety might reasonably ask, "Why are they Class 3a? Why not Class 2?"
The answer is related both to apparent brightness and to cost. Most inexpensive laser pointers use laser diodes that produce light with wavelength 670 nm, because those diodes are inexpensive. But 670 nm light is deep in the red part of the spectrum, where the eye isn't very sensitive. This makes the spot from a Class 2 670 nm laser pointer hard to see on a brightly-lit projection screen. To compensate for this lack of apparent brightness, many manufacturers increase the power to Class 3a levels.
The older HeNe units produced orange-red light with wavelength 633 nm. This light has several times the apparent brightness of 670 nm light, so Class 2 HeNe pointers were adequately bright. Pointers now are available with 635 nm diodes, although they cost more than twice as much as the 670 nm units. These mimic the HeNe brightness and also are adequate at Class 2 power; however, it is difficult to find the 635 nm pointers in Class 2 C for reasons that I fail to understand, most of these units also are Class 3a. In the figure below, it is easy to see that, at the same power, a 635 nm pointer has about five times the apparent brightness of a 670 nm unit.
Recently, 532 nm wavelength green solid-state (neodymium-yttrium, not diode!) pointers have become available. They are very bright and pleasing (nearly 20 times the apparent brightness of 670 nm units), but they also are more expensive than the red diode units C $120. But, that's still affordable, and it's far less than the $400+ that green diode pointers once cost. And, the price probably will continue to come down.
Nearly all consumer-level pointers, including the new green ones, are Class 3a. How dangerous are Class 3a laser pointers when used as intended?
The quick answer is, "Not very." In a typical presentation situation, the speaker will be pointing the device away from the audience. And if he/she accidentally fires the unit into the audience while gesticulating, the probability of the beam entering someone's pupil is small, and the exposure is likely to be very brief. Furthermore, in this scenario, the pointer will be in motion and the image on the victim's retina will be a stripe rather than a point.
Although the risk of an injury from such an exposure is small (but not zero), there may be liability issues. As stated earlier, such an exposure can exceed the exposure limits of recognized standards. If an audience member is exposed, it would be very difficult for the speaker or his/her employer to prove that the victim was in fact not overexposed. And any organization that has adopted the ANSI Z136 standard for laser safety will find it difficult to allow persons without laser safety training to use Class 3a lasers in an uncontrolled environment, while remaining in compliance.
The situation may be quite different if the laser pointer is in the hands of someone who is not a responsible adult. These are not toys! A child or adolescent might, as a result of carelessness, ignorance, or even a dare, stare into a laser pointer long enough to cause retinal injury. Even Class 2 lasers theoretically are capable of causing retinal injury if the person overcomes his/her eyeblink reflex and stares into the beam for more than 3 second. Children and adolescents should be closely supervised if they are allowed to operate any laser pointer. Ditto for teenagers, or anyone who is maturity-challenged.
Recommendations for laser pointer safety:
Avoid Class 3a when possible. Although Class 2 670 nm units aren't very bright, they are useable. I know of one manufacturer that makes a Class 2 635 nm pointer, and it is entirely adequate even on brightly-lit projection screens...but it is hard to find, and I know of no others.
And the current 532 nm units are also Class 3a. Treat laser pointers like guns. Although they of course aren't capable of causing injuries as severe as those from guns, like guns they can injure at a distance. And even if they don't injure directly, they can startle victims and cause accidents. The term "laser rage" has been coined to describe the reaction of some people to being unexpectedly dazzled by laser pointers. I repeat, laser pointers are not toys! Don't let children or adolescents play with them, or use them without close supervision.