March 21, 2013
NIST Finds That Many Laser Pointers Do Not Meet Federal Guidelines
April Flowers for redOrbit.com - Your Universe Online
Researchers from the National Institutes of Standards and Technology (NIST) recently demonstrated a low-cost apparatus designed to quickly and accurately measure the properties of 122 commercially available handheld laser pointers. The scientists found that nearly 90 percent of green laser pointers and approximately 44 percent of red laser pointers were out of compliance with federal safety regulations. The NIST test apparatus was designed so that it could be easily replicated by other institutions for verification.The study results were reported at the International Laser Safety Conference this week, and will be published in the Journal of Laser Applications. At the conference, the research team reported that both red and green laser pointers often emit more visible power than allowed under the Code of Federal Regulations (CFR). Green pointers emit unacceptable levels of infrared light as well.
Although anecdotal reports of the dangers of green lasers have previously appeared in scientific journals and the public media, the new NIST tests are the first precision measurements of a large number of handheld laser devices. Surprisingly, the NIST test revealed that many red leaser pointers are also out of compliance with CFR, raising numerous safety questions regarding laser pointers and their use.
The researchers randomly selected commercial laser devices labeled as Class IIIa or 3R sold as suitable for demonstration use in classrooms and other public spaces for testing. Under the CFR, such lasers are limited to 5 milliwatts maximum emission in the visible spectrum and less than 2 milliwatts in the infrared spectrum. Approximately 50 percent of the devices tested emitted power levels at least twice the CFR limit at one or more wavelengths, with the highest measured output being 66.5 milliwatts. This is more than ten times the legal limit. The NIST power measurement tests are accurate to within five percent.
Green laser light is generated from infrared light. The device should ideally be designed and manufactured to confine the infrared light within the housing. The new NIST results, however, show that more than 75 percent of the tested devices emit infrared light in excess of the CFR limit.
Laser devices that exceed 3R limits, according to the American National Standards Institute (ANSI), may be hazardous. ANSI recommends more rigorous controls, such as training, to prevent injury.
A non-regulatory agency with decades of experience, NIST provides industry, research and military agencies with laser power measurements traceable to international standards. NIST has a history of innovation in creating testing devices to make such measurements. The laser pointer test bed was built by technical staff from NIST's Laser Radiometry Project in collaboration with the NIST Office of Safety, Health and Environment. The data on laser pointer power generated by the NIST test has been provided to the Food and Drug Administration (FDA), which regulates laser product safety.
As reported online in the journal Measurement Science and Technology, the test measurement bed was designed by NIST Laser Safety Officer Joshua Hadler. The test bed system consists of a laser power meter and two optical filters used to quantify the emissions of different wavelengths of light in both the visible and infrared spectrums. The power meter and filters were calibrated at NIST. The device also employed lens holders to ensure repeatable laser alignment, and an adjustable aperture to contain the laser light around the output end of the laser.
"The measurement system is designed so that anyone can build it using off-the-shelf parts for about $2,000," Hadler says. "By relying on manufacturers' traceability to a national measurement institute such as NIST, someone could use this design to accurately measure power from a laser pointer."
Image 2 (below): NIST laser safety officer Joshua Hadler and his apparatus for measuring the properties of handheld laser devices. Credit: Burrus/NIST