Quote:
Originally Posted by cooper barrett
Cough,
Explain could definitely?
Scientific American
In FDA-regulated pointers, the laser power limit is set at one-tenth the actual threshold of damage. If a person sees a bright light, they will automatically blink, on the average in less than 0.2 seconds. This is referred to as the blink reflex, and it is considered when the limit is assigned for how much power will cause an eye injury. By the way, you shouldn't force a stare at a laser, just like you shouldn't stare at the sun or any bright light source.
Possible more potentially damaging -- although not to the eye -- is that a regular pointer laser can overwhelm the eye with light, typically called flash blindness. If a person is walking a rocky path, operating machinery, a vehicle or aircraft, this temporary loss of vision could cause injury or disaster. At night, when the pupil is most open, the effects would be magnified.
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I would mostly agree with what you said. For low powered laser pointers, there is a low risk of blindness. However, the article you referred to is talking about red laser pointers, green laser pointers are a much different story.
1) Cheap green laser pointers do not emit just a clean 532nm line. Green laser ponters are DPSS lasers. An 808nm infrared diode pumps a NdYV04 crystal which emits a 1064nm beam. That beam enters a KTP crystal and gets frequency doubled to produce the visible 532nm green beam that you see from the laser pointer. If proper filtering isn't applied, and in cheap laser pointers, it often isn't, then the infrared light being emitted from the laser pointer can be up to 10x higher than the rated output power.
2) Green is also absorbed more readily by the human eye than red. In fact, a green laser with the same output power as a red laser is 30x more visible. The green 'cone' in your eye is most sensitive at 535nm. Green lasers output 532nm light.
3) It is ridiculously easy to get a high powered green laser. A search on alibaba will bring back a ton of >5mW handheld lasers. These lasers are class IIIb which can cause eye damage pretty quickly. The Nominal Ocular Hazard Distance (NOHD) for a lower-powered 50 mW Class 3B visible-beam laser with a tight beam (0.5 milliradian divergence) is 330 ft.
I've worked on a few lasers in my time. Still no eye damage.
