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Green laser pointers have become a democratic consumer item , delivering lighter that ’s brighter to the heart than red lasers , but news report have circulated on the web about the potential hazards of cheap role model .
A team led by physicist Charles Clark at the National Institute of Standards and Technology ( NIST ) recently put some Book of Numbers to the problem . In one eccentric , the grouping find that a greenlaser pointeremitted almost twice its rank superpower level of light – but at invisible and potentially grave infrared wavelengths rather than green .
A new NIST study describes the nature of the problem and propose instructions for a home test using an cheap webcam that can detect surplus infrared lighting from greenish lasers .
Green alert
Late last year , the NIST enquiry team purchased three low - cost green laser pointers advertised to have a king output signal of 10 milliwatts ( mW ) .
Measurements demonstrate that one social unit emitted dim green light butdelivered infrared levelsof intimately 20 mW – powerful enough to cause retinal damage to an individual before he or she is cognizant of the invisible light .
NIST ’s Jemellie Galang and her fellow worker repeated the tests with several other optical maser pointer and found similarly intense infrared emission in some but not all building block .
Technical difficulties
The problem stems from inadequate procedures in manufacturing character self-confidence , agree to the research team .
Inside a green optical maser pointer , infrared lighter from a semiconductor unit semiconductor diode optical maser pumps infrared illumination at a wavelength of 808 nanometers into a transparent crystal of yttrium orthovanadate doped with neodymium corpuscle , causing the crystal to lase even deeply in the infrared frequency , at 1064 millimicron .
This sparkle give-up the ghost through a lechatelierite of potassium titanyl phosphate ( KTP ) , which emits visible light of half the wavelength : 532 nanometer , the intimate color of the green optical maser pointer .
However , if the KTP crystal is misalign , little of the 1064 - micromillimeter light is convert into green light , and most of it comes out as infrared . superfluous infrared escape can also come if the finish at both ends of the quartz glass that act as mirrors for the infrared optical maser light are too thin .
Solution at hand
The NIST team says this problem could be solved by contain an inexpensive infrared filter at the ending of the laser , which could reduce infrared emission by 100 - 1000 times depending on quality and cost .
Although these filter exist inmodern digital camerasand more expensive light-green optical maser pointers , they often are left out of the cheap models .
The squad demonstrates a place trial that laser hobbyists could conduct to discover exuberant infrared escape , by using a mutual digital or cell phone television camera , a compact disk , a webcam and a boob tube remote control .
Regardless , they say possessor of the devices should never point the lasers at the heart or aim them at open such as windows , which can reflect infrared Christ Within back to the exploiter – a peculiarly subtle hazard because many modern energy - saving windows have coating designed specifically to reflect infrared .
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