Can I Safely Use a Laser Pointer?
Guest Contributor Ken Barat, Certified Laser Safety Officer, Lawrence Livermore National Laboratory
Over the last few years laser pointers have received attention in the press and aroused some public concern. As a consumer product, laser pointers are designed to be safe when used for their intended purpose. Unfortunately, however, the laser pointer can easily be misused.
The early laser pointers were helium-neon (HeNe) gas lasers and generated laser radiation at 633 nanometers (nm). These pointers were usually designed to produce a laser beam with an output power no greater than 1 milliwatt (mW). According to the ANSI classification scheme (ANSI Z136.1-1993, American National Standard for Safe Use of Lasers) a visible laser (400-700 nm) operating at less than 1 mW power is a Class 2 laser, for which the blink reflex normally affords adequate eye protection. Retinal injury is possible with a Class 2 laser if a person deliberately overcomes his/her natural aversion response in looking at the beam.
The next generation of laser pointers used diode lasers as the optical source. Diode laser pointers initially yielded beams at 690 nm. The difference between 633 and 690 nm may seem small as both are visible red wavelengths, but the difference is large as interpreted by the human eye. The eye sees 633 nm five times brighter than it sees 690 nm. This explains why the first diode laser pointers needed an output of 5 mW to equal the brightness of a 1 mW pointer at 633 nm.
From a laser safety point of view, the situation grew more complex as new diode lasers were developed producing light at 670, 650, and 640 nm. As wavelengths emitted by diode lasers have gotten shorter, the power output level has stayed at 5 mW.
So today we have 5 mW laser pointer beams at 640 nm that are extremely bright to the eye. In addition, an even brighter pointer is now on the market whose wavelength is at 533 nm (green). This new technology uses a frequency-doubled Neodymium:YAG laser with a blocked infrared component.
Visible laser pointers operating with 1-5 mW power are Class 3a and can be hazardous if viewed even for a very short time. Users should never look directly into the beam of Class 3a laser pointers, which are required by Food and Drug Administration (FDA) regulations to be marked "DANGER." (Class 2 lasers are labeled "CAUTION.") Possible hazards include startle effects, flash-blindness, glare, and after-images if a person is struck directly in the eye. Numerous cases of such incidents have been reported, along with cases where individuals overreacted to being flashed. Reports of those exposed include a pilot, bus drivers, sports figures, a teacher, and police (e.g., see the Rockwell Laser Industries articles).
In 1997 the FDA issued a warning on misuse of laser pointers (see Consumer Information on CDRH Topics). In some states, such as California, it is a criminal misdemeanor to shine a laser pointer at individuals who perceive they are at risk, and it is a felony to aim one at an aircraft. Some local governments have passed regulations requiring anyone purchasing a laser pointer to be 18 years of age or older. It is expected that the pending revision of ANSI Z136.1 will have a special section commenting on laser pointers.
In summary, laser pointers are helpful tools but they must be used responsibly. Common sense dictates that users should never direct a laser pointer beam at another person. And lasers with power over 5 mW should not be used as pointers.
Three NCRP Reports deal with the RF safety:
- No. 67 on quantities and units,
- No. 86 on biological effects and exposure criteria, and
- No. 119 on evaluations and measurements of practical systems.
See the NCRP website for more information.