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08-13-2010, 12:28 PM #33
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Grix
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Re: laser prison

Quote:
 Originally Posted by Thengine You are right, the eye (pupil) is 7mm wide at night and 4mm wide during the day. So a 100mw laser with a divergence of 1.5mrads = 800 ft = 243 Meters divergence of 1.5mm per Meter * 243 Meters = Diameter of: 1.5mm + 1.5*243 = 367 mm diameter of the dot at 800 ft. Area of dot in Meters = Pie * .367 ^2 = .423 square meters. I am not sure about your math, I think that this is the correct formula/answer for the area at 800ft. The area of a fully dilated pupil is Pie * .007 M ^2 = .000154 M^2 so the percentage of 100mw entering each individual eye is .000154 / .423 = .036 PERCENT .00036 * 100mw = .036 mw That means that .036 mw is entering each eye at 800ft, through the cockpit, at a moving target. A worse case scenario of .05 seconds exposure is being severely generous and I would think overestimates the ability of a handheld laser to be kept on target at that distance. Its a lot worse then what Grix said (at .0007 mw,) but that sounds an awful lot like a night light to me. I would consider this mathmatical proof that there is little to no danger from a theoretical \$45 laser at the stated distances. It would most likely show up as a flashlight (.423 m^2 area) on the outside of the aircraft. Get a little closer like take off and landing and you have a totally different story. I think thats where the true teeth of the law belongs. Only someone with malicious intent (terrorist) would point a laser at a pilot focusing on the runway.
Whops, somehow I thought the beam diameter would be 3,6m after 800 feet, not 0,36m. Thanks for correcting me.

But yeah, the article is two years old, and two years ago a 100mW laser did not cost £30. It was probably a 5-30 mW laser.

08-13-2010, 03:52 PM #34
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qumefox
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Re: laser prison

Quote:
 Originally Posted by Thengine Thats a really neat story, it seems to be following a pattern. Police helicopter pilots (without passengers) are always "temporarily blinded." Notice that the Jet pilot didn't have any problems reported? They don't want to scare the people that fly, and yet I find that the Jet being closest (on takeoff and landing) to the ground is the most likely candidate for actual "temporarily blindness." I think this prosecution falls under the category "contempt of cop." Damn.. 6 months.. 180 days.. thats A LOT of soap to drop. I hope this guy learns to put his soap on a rope.
You have to factor in the aircraft type into this comparison. Commercial airliners don't have as much of a problem for two reasons. First of all the cockpits are usually relatively illuminated even at night. There are a LOT of things that light up in the cockpit of a commercial airliner so the pilots never really become night adjusted. The second factor is that, compared to other aircraft, the relative window surface area is TINY.

Now compare this to a helicopter. Most are going to be >80% transparent canopy. Usually some type of polycarbonate formed into a bubble, and usually not in pristine condition, meaning it'll have scratches, nicks, etc.. this matters, a lot.. even if they aren't bad enough to noticeably affect visibility. If it's a piston driven heli, it's going to usually have a minimal gauge set depending on the engine and they are going to generally be centrally located on most small heli's that non-rich police departments like to use. Robinson R44's etc. A gas turbine heli will have a larger gauge set, but still have the same basic features. Less light sources in the cockpit at night so the pilot will be far more night adjusted.

Now back to that polycarbonate... have you ever shined an unfocused laser at a scratched up piece of clear plastic before? This simulates pretty well how the canopy of a helicopter looks when hit by a divergent beam.. Every little nick and scratch and imperfection lights up like you wouldn't believe.. Especially when your dark adjusted.

This is the reason you hear about this from heli pilots a lot more than anyone else.

08-13-2010, 04:11 PM #35
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kiyoukan
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Re: laser prison

Okay but from what your saying is that the bubble will block a good amount of the very diverged light and even more so if there are scratches.
So the pilot might lose sight but never damage and to pull a dangerous maneuver for a illuminated windshield make even less sense.
Its like say the sun was in your eye so you punched the gas to get out of its way, instead of just turning away from the source.
Heli are nice for the fact they can hover so if you lose sight you can stop moving and just wait, you dont have to worry about flying into anything as well as from the state of most windshield are scratched up it would be the same as putting leds around the window and then suddenly turning them on it might spook you but give your self a few second and your good.
Dont get me wrong that the guy did something dumb and needs to be punished but why put him in jail where i pay for him to be there?
Give him 100 hours of comunity service as well as some class to teach him what he did was wrong and end it.
Hes not a menace to society.
He can still work a job and pay taxes so we can keep the real menaces in jail.
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08-13-2010, 05:42 PM #36
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qumefox
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Re: laser prison

This isn't about eye damage.. This is about losing your night adaption. Having the canopy illuminated will do just that. Go outside at night, let your self get night adjusted, then shine a cheap keychain LED light in your face and see how long it takes you to see again. Helicopters aren't exactly easy to fly either, and I can't think of any pilots who'd welcome such a distraction.

Jail time isn't 'too harsh' in these cases because these aren't hardcore repeat offenders who don't care if they go to jail we're talking about. They're just people that have bad judgement and lack common sense. You'll never have massive amounts of these people going to jail. A few cases are enough to show everyone else that it's just not a smart thing to do. If they knew there was a chance they'd go to jail they likely never would have done it. So the tax burden incurred by these individuals will me minimal verses the message it sends to he general public.

Besides, in the US at least, it'd be unlikely you had to serve more than 1/4 your term anyway, if even that, before being released on probation. Not for this particular crime anyway.

08-13-2010, 08:26 PM #37
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Toaster
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Re: laser prison

A pilot can hold a helo steady without having to look at gauges you know.

Also testing below 500AGL is idiotic as no responsible pilot is gonna fly that low.

And there is no need to have the beam in some mount to make sure it hits their eyes because the dumbasses doing this don't mount them. You guys are thinking this way too much.

08-13-2010, 08:28 PM #38
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Toaster
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Re: laser prison

Quote:
 Originally Posted by qumefox Helicopters aren't exactly easy to fly either, and I can't think of any pilots who'd welcome such a distraction.
That sir is an opinion. And an opinion in which you even said you had no experience as a pilot.

08-13-2010, 08:33 PM #39
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kiyoukan
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Re: laser prison

i do wonder where the danger level is. at what point is the power of the laser able to do real damage besides make someone lose night vision.
Any one want to crack the numbers and lets just say the cockpit takes 20% of the final power out.
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I have lots of lasers.
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I have a projector small only 2.5W
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08-13-2010, 08:36 PM #40
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Toaster
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Re: laser prison

I think the danger level also correlates with the pilots IQ and experience and their attitude either as a tight ass or a relaxed person

08-13-2010, 08:38 PM #41
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kiyoukan
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Re: laser prison

i meant more of eye damage what power would you need to do damage. i would like to know the math that way if i do use all 2.2W of laser i know that it should not blind him.
I would much rather not but i somehow think he would go so far to fly into it to prove a point....
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I have lots of lasers.
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I have a projector small only 2.5W
I have other toys. What its plain and simple.

08-13-2010, 08:43 PM #42
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Toaster
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Re: laser prison

I can promise you he will be fine. a lot of the power is also lost from hitting shit in the air. He will be able to hold it steady. no pilot in their right mind would even fly below 500 and the beam isn't precisely aimed by these crazies.

08-13-2010, 11:34 PM #43
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Thengine
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Re: laser prison

Quote:
 Originally Posted by kiyoukan i meant more of eye damage what power would you need to do damage. i would like to know the math that way if i do use all 2.2W of laser i know that it should not blind him. I would much rather not but i somehow think he would go so far to fly into it to prove a point....
You do the NOHD numbers separate for each laser, not putting them altogether. Or that would be like saying 1,000 50mw lasers is = 50W of laser, I don't really think you are going to be able to have them all focused on the same spot. So pick the most powerful laser, find the NOHD for it:

You are figuring 20% of the light is going to be lost by the canopy, then to get the new NOHD numbers we need to find at what percentage of the distance 80 percent of the light = 100 percent at NOHD

It is really simple, take 100 percent and subtract the light lost: 1-.2 = .8
Now we need to take the square root because light looses its power as a square of distance. .8 ^.5 = .894
.894 * NOHD = new NOHD
This is a simplistic calculation but all things being equal it should hold.

08-14-2010, 01:27 AM #44
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Fonduman
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Re: laser prison

Quote:
 Originally Posted by rikgrimsby must be some thing about kids in the uk heres another one and this is this week Laser pen yob jailed - The Star
the worst thing possibly about all this hype at the moment is that laser pen is becoming synonymous with yob. I mentioned elsewhere, I was shining a few lasers into the sky outside my house a while back, and everyone in the street started locking their doors. granted, 1W of 445 will do that to the laserly ignorant , but you'd have thought i was throwing bricks at peoples windows instead of enjoying my educational and fun, more or less harmless, hobby.
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Just starting off my collection. Currently have:
150mW 405nm from O-like *outputting 156mW quite stable*
Jayrob SS 18650 kit, A140 diode at 1A putting out 900mW
100mW 532nm from dealextreme *broke*
500mW 532nm from O-like *lense dmg? down to 150mW with scatter*

200mW waterproof 650nm from O-like *outputting 210mW quite stable*
Plan to have soon:
1W 455nm from wicked lasers (ofc)

01010000011000010111001101110100011000010010000001 10111000100000011100110110000101110101011000110110 01010011101000100000011010010111010001110011001000 00011000010110110101100010011010010110011101110101 01101111011101010111001100100001

08-14-2010, 01:50 AM #45
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qumefox
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Re: laser prison

Quote:
 Originally Posted by Toaster That sir is an opinion. And an opinion in which you even said you had no experience as a pilot.
And you've shown no proof that you do either. At least i'm not claiming to be something i'm not, so until you prove you have experience flying yourself, then it's all opinions.

I know the only REAL pilot I know, at least that talks about lasers, has stated he didn't enjoy the experience, it ruined his night adaption when it happened, and said he would hate for it to happen on approach.

I'm honestly not sure why this topic is even being debated. Illuminating aircraft (as well as cars) is an exceedingly stupid thing to do. The technicalities about it don't really matter.

Last edited by qumefox; 08-14-2010 at 02:06 AM.

08-14-2010, 04:37 AM #46
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Thengine
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Re: laser prison

Quote:
 Originally Posted by Toaster A pilot can hold a helo steady without having to look at gauges you know. Also testing below 500AGL is idiotic as no responsible pilot is gonna fly that low. And there is no need to have the beam in some mount to make sure it hits their eyes because the dumbasses doing this don't mount them. You guys are thinking this way too much.
I used to fly nap o da Earth with my OH-58D Kiowa warrior. Sometimes we came back and the tail fin would be plastered green because the tail rotor would become a weed wacker

Nap-of-the-earth - Wikipedia, the free encyclopedia

I believe I am a responsible pilot and flying low is no big deal. It just takes very good instruction on how to do it safely.

I am curious why you think that "testing below 500AGL is idiotic as no responsible pilot is gonna fly that low."

Are you a helicopter pilot? I am leaning towards agreeing with qumefox atm:

"And you've shown no proof that you do either. At least i'm not claiming to be something i'm not, so until you prove you have experience flying yourself, then it's all opinions."

08-14-2010, 05:14 AM #47
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qumefox
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Re: laser prison

Quote:
 Originally Posted by Thengine I used to fly nap o da Earth with my OH-58D Kiowa warrior. Sometimes we came back and the tail fin would be plastered green because the tail rotor would become a weed wacker

Quote:
 I believe I am a responsible pilot and flying low is no big deal. It just takes very good instruction on how to do it safely.
You do know those two statements of yours kind of disagree with each other.

I may not be a pilot yet, but that doesn't mean I haven't researched it, and rotorcraft are my primary interest. From what i've read/heard/talked to people about... ANYTHING impacting the tail rotor is a BAD thing... You lose the tail rotor, your F'd at that altitude. I don't see how an autorotation would be possible when your already in the trees. It's the whole 'flying above the curve' deal.

08-15-2010, 05:54 PM #48
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Toaster
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Re: laser prison

QuemeFox you just like to pick fights so i am gonna quit here.

I fly planes not helos, and why would your rotor be covered, the skids are lower than the rotor so how did you not hit the skids and eat it?

Below 500 yeah people can and do fly but 99% of aircraft in residential aircraft are above that. (You know above houses and cities)
For the sake of the test I think it should be higher.

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