by neufer » Fri May 18, 2018 7:12 pm
Chris Peterson wrote: ↑Fri May 18, 2018 6:13 pm
neufer wrote: ↑Fri May 18, 2018 5:44 pm
- 300 W/m2 would feel kind of nice on one's skin;
however, coming effectively from a point source
staring at it would be much worse than staring at the Sun.
Given an eye pupil size of 2 mm (typical when viewing bright light), inserting your eye into a beam with a power density of 300 W/m
2 means you're receiving 1 mW. The same as if you looked directly into the lowest power laser pointers. Staring at these is less dangerous than staring at the Sun.
Well...one's eye pupil size may be only 2 mm on a bright sunny day but
not at night... at least not at first.
And I would imagine that laser pointer spots are also larger than 2 mm.
https://en.wikipedia.org/wiki/Laser_safety wrote:
Class II (Output power may be
up to 1 mW): The blink reflex (glare aversion response to bright lights) of the human eye will prevent eye damage, unless the person deliberately stares into the beam for an extended period.
Intentional suppression of the blink reflex could lead to eye injury. (Some laser pointers and measuring instruments are class 2.)
Class IIa: A region in the low-power end of Class II where the laser requires in excess of 1000 seconds of continuous viewing to produce a burn to the retina. Commercial laser scanners are in this subclass.
https://www.physics.utoronto.ca/~jharlow/teaching/lasers.html wrote:
Are Laser Pointers Dangerous to Pilots?
by Jason Harlow
My Experiment:
I took 3 different green laser pointers, all 5 mW, all of which were purchased for less than $50 each. I measured the spot size at 1, 10, 15, 40 and 97 m. I then plotted distance versus beam diameter and did a best-fit linear slope. I found a slope of 1.04 +/- 0.09 mm/m and a y-intercept of 1.4 +/- 0.5 mm. This means that, at the laser pointer itself, the beam diameter is about 1.5 mm. As it travels, the diameter increases by 1 mm for every 1 m away from the laser pointer.
At a distance of 5 m away from the laser, the beam diameter is 7 mm, which is a typical diameter of the dark-adapted pupil (Bradley JC, Bentley KC, Mughal AI, Bodhireddy H and Brown SM 2011, Journal of Refractive Surgery, v.27 issue.3, pg.202). This means that if you are within 5 m of the laser and it is shot directly into one of your dark-adapted pupils, all 5 mW of power will enter your eye, and then be focused onto your retina.
At a distance of 10 m, the beam diameter is 12 mm, and its area is 110 sq-mm. Since a 7 mm-diameter dark-adapted pupil has an area of 34 sq-mm, only 1.5 mW of power will enter your eye if this laser is shot directly in.
At 100 m, the beam is 10 cm in diameter with an area of 8700 sq-mm, which is 250 times bigger than your dark-adapted pupil. The maximum power which can enter your eye at this distance is 0.02 mW.
At a distance of 1 km, which would be typical for a low-flying aircraft, the maximum power which could enter a pilot's eye is 0.0002 mW, or 0.2 micro-Watts.
Note that Class 1 lasers have powers less than 0.024 mW, and they carry no warning label because they are incapable of causing eye damage. My little experiment indicates that a Class 3A laser-pointer (5 mW) becomes equivalent to a Class 1 laser at a distance of 90 m or farther.
As for actual retinal damage, it has been estimated that it would take 10 seconds of staring directly into a class 3A laser in order to damage your retina. But, in practice this is impossible to do because it feels very painful and you immediately look away.>>
[quote="Chris Peterson" post_id=282611 time=1526667229 user_id=117706]
[quote=neufer post_id=282610 time=1526665446 user_id=124483]
[list]300 W/m[sup]2[/sup] would feel kind of nice on one's skin;
however, coming effectively from [b][u][color=#FF0000]a point source[/color][/u][/b]
staring at it would be [b][u][color=#FF0000]much worse[/color][/u][/b] than staring at the Sun.
[/quote]
Given an eye pupil size of 2 mm (typical when viewing bright light), inserting your eye into a beam with a power density of 300 W/m[sup]2[/sup] means you're receiving 1 mW. The same as if you looked directly into the lowest power laser pointers. Staring at these is less dangerous than staring at the Sun.[/quote]
Well...one's eye pupil size may be only 2 mm on a bright sunny day but [b][u]not at night[/u][/b]... at least not at first.
And I would imagine that laser pointer spots are also larger than 2 mm.
[quote=" https://en.wikipedia.org/wiki/Laser_safety"]
Class II (Output power may be [b][u]up to 1 mW[/u][/b]): The blink reflex (glare aversion response to bright lights) of the human eye will prevent eye damage, unless the person deliberately stares into the beam for an extended period. [b][u]Intentional suppression of the blink reflex could lead to eye injury.[/u][/b] (Some laser pointers and measuring instruments are class 2.)
Class IIa: A region in the low-power end of Class II where the laser requires in excess of 1000 seconds of continuous viewing to produce a burn to the retina. Commercial laser scanners are in this subclass.[/quote][quote=" https://www.physics.utoronto.ca/~jharlow/teaching/lasers.html"]
Are Laser Pointers Dangerous to Pilots?
by Jason Harlow
My Experiment:
[b][u][color=#00BF00]I took 3 different green laser pointers, all 5 mW, all of which were purchased for less than $50 each.[/color][/u][/b] I measured the spot size at 1, 10, 15, 40 and 97 m. I then plotted distance versus beam diameter and did a best-fit linear slope. I found a slope of 1.04 +/- 0.09 mm/m and a y-intercept of 1.4 +/- 0.5 mm. This means that, at the laser pointer itself, the beam diameter is about 1.5 mm. As it travels, the diameter increases by 1 mm for every 1 m away from the laser pointer.
At a distance of 5 m away from the laser, the beam diameter is 7 mm, which is a typical diameter of the dark-adapted pupil (Bradley JC, Bentley KC, Mughal AI, Bodhireddy H and Brown SM 2011, Journal of Refractive Surgery, v.27 issue.3, pg.202). This means that if you are within 5 m of the laser and it is shot directly into one of your dark-adapted pupils, all 5 mW of power will enter your eye, and then be focused onto your retina.
At a distance of 10 m, the beam diameter is 12 mm, and its area is 110 sq-mm. Since a 7 mm-diameter dark-adapted pupil has an area of 34 sq-mm, only 1.5 mW of power will enter your eye if this laser is shot directly in.
At 100 m, the beam is 10 cm in diameter with an area of 8700 sq-mm, which is 250 times bigger than your dark-adapted pupil. The maximum power which can enter your eye at this distance is 0.02 mW.
At a distance of 1 km, which would be typical for a low-flying aircraft, the maximum power which could enter a pilot's eye is 0.0002 mW, or 0.2 micro-Watts.
Note that Class 1 lasers have powers less than 0.024 mW, and they carry no warning label because they are incapable of causing eye damage. My little experiment indicates that a Class 3A laser-pointer (5 mW) becomes equivalent to a Class 1 laser at a distance of 90 m or farther.
As for actual retinal damage, it has been estimated that it would take 10 seconds of staring directly into a class 3A laser in order to damage your retina. But, in practice this is impossible to do because it feels very painful and you immediately look away.>>[/quote]