Green lasers can present eyesight risk

WASHINGTON, Aug. 4 (UPI) -- Green lasers, brighter than red lasers and a popular consumer item, could be a hazard by emitting dangerous levels of infrared radiation, U.S. researchers say.

Scientists at the National Institute of Standards and Technology testing inexpensive green laser pointers found some emitted almost twice the rated power level of light -- but at invisible and potentially dangerous infrared wavelengths rather than green, an NIST release said Wednesday.

One pointer rated a 10 milliwatts delivered only weak green light but emitted infrared levels of almost 20 milliwatts, enough to cause retinal damage.

Tests of other laser pointers found similar intense infrared emissions.

The problem is caused by inadequate quality control in the manufacturing process, NIST researchers said.

If crystals in the pointer that generate the laser light are misaligned, they said, little of the light comes out as green and most of it comes out as infrared.

The problem could be solved with an inexpensive infrared filter at the end of the laser, which could reduce or block infrared emissions.

Although such filters are used in modern digital cameras and more expensive green laser pointers, they often are left out of the inexpensive models, the NIST said.