Laser pointers blinding pilots? Sounds implausible

[skbuncks]

A quick scout around ebay* shows that the green lasers available for around $5 (or around £10 in the UK) are advertised as:


Output Type :Fixed focus, continuous output and working time of over 5,000 hours
Dimension :14 x 160mm
Output power: 5mW (Class IIIb)
Wavelenth: 532nm
Works with 2 AAA battery (not included)
Body material: Metal
Body color: Black & Siliver


The use of Roman numerals in the power output classification signifies it is rated against the American Classification Standard. In the UK they would be Class 3R.
A guide on the classification is here.

Class 3R lasers are higher powered devices than Class 1 and Class 2 and may have a maximum output power of 5 mW or 5 times the Accessible Emission Limit (AEL) for a Class 1 product. The laser beams from these products exceed the maximum permissible exposure for accidental viewing and can potentially cause eye injuries.

Furthermore as green lasers are 30 times brighter to the human eye than red lasers at the same radiant power the beam can at times be clearly visible.
There are numerous examples of 5mW green lasers available over the net and plenty of anecdotes of them being used for astronomical purposes...

Perfect for teaching Astronomy to Cub and Boy Scouts. Product worked exactly as advertised and had 4mw output, which is within the acceptable range. If you want a true 5mw output pointer, you need to get the more expensive hand selected ones, but that is overkill.

http://www.5mwgreenlaserpointers.com/

...if anecdotes and youtube clips are to believed then I see no reason why a cheap $5 5mW green laser pointer couldn't be used to dazzle pilots.


skb

* ebay search term '5 mW 532nm Green Beam Laser Pointer Pen'.

[Legaleagle]

Further I think we need to factor in the fact that there is a co-pilot, and multipile automatic controls to prevent crashing.

Only in a commercial aircraft.

What about the private pilot, in a light aircraft, who might have some passengers on board, who's 50-100 feet off the ground on final approach, into the sunset, straining every occular muscle to focus on the runway centreline. Suddenly someone on or near the fringe of the runway shines a laser pen direct into the pilot's eyes. I would not want to be in that position. Although a crash is unlikely, the potential is there.

I personally think of it as being of the same kind of magnitude of offence as throwing stones at trains. It may be that it is unlikely to cause an accident but it's a bloody stupid thing to do anyway.

[Harryprice]

... into the sunset, straining every occular muscle to focus on the runway centreline. Suddenly someone on or near the fringe of the runway shines a laser pen direct into the pilot's eyes ...

Do you write novels in your spare time?

[Matt]

Another thought just occurred to me:

What's so special about lasers?

Laser light is highly collimated. This increases the range at which their light can be harmful.

Laser Light is of a single spatially coherrent wavelength. This coherrence may lead to constructive interference within the eye.

That all the power of the light is concentrated at one frequency may mean that parts of the retina sensitive to that frequency may be damaged before the blink reflex (which depends upon the total power across the visible range)

By analogy suppose I didn't want a cake to be squished so I placed it upon a set of scales wired to an alarm. If the scales felt a weight large enough to squish the cake it woudl sound an alarm however smaller weights would be allowed for some reason. There woudl therefore be wieghts that if spread across the full surface fo teh cake woudl not soudn the alarm but if focussed upon a knife point woudl indeed damage the cake. That's how our eyes defences are wired up.

The effects of laser on piots are real and documented

Here we go http://www.ntsb.gov/recs/letters/1997/A97_13_15.pdf

Accurate aiming is only a problem for someone making a targetted attack. The risks to pilots are only mittigated by a low hit rate if this rate isn't compensated for by a large number of opportunities for accidental contact.

We consider that being hit by lightning is a rare occurence. But there are so many lightning storms and so many people that even with the low probability of any particular individual being hit it stall happens to an average of half a dozen people a day.

[Legaleagle]

Do you write novels in your spare time?

Yes!

[Cuddles]

I'm not denying that it's theoretically possible to aim a sufficiently powerful laser at a pilot's eye and cause temporary dazzling. I am sceptical that it has every actually happened as a consequence of a cheap hand-held laser pointer, the kind they said could be bought for around $5.

Note the heading of the thread. I will say it again, that I fully understand that lasers are potentially dangerous things. I even know that defence companies have been attempting to build blinding weapons from lasers, however the title of the article I was responding to was "Cheap laser pointers from eBay used to blind aircraft pilots".

I have no idea what point you are trying to make here. That's exactly the kind of laser we're talking about.

Edit: In addition to skbunks' post referring specifically to things found on eBay, a few seconds with Google will turn up plenty of websites where you can buy pointers with as much power as 300mW, powerful enough to melt plastic, burn things and cause eye damage just from reflections, let alone the main beam. Of course, these are a little more expensive than $5, but it's not particularly expensive to get something as powerful as 100mW.

This is my other problem:

We all know that a prolonged direct hit to the eye can cause dazzling or even permanent damage.

What we should all know is that an extremely short direct hit to the eye will certainly cause dazzling. Again, I will ask if no-one has ever reflected light off a watch or something into your eye? This is something that's so common it's even featured in things like Futurama. Given how much more powerful a laser is likely to be than something like that, how can you possibly question whether it would dazzle someone, regardless of any permanent damage?

And let's not forget: We are trying to target a moving object. The only position from where this would be an 'easy' hit would be if you were directly in it's flight path: For example, if you were standing just beyond the runway and shining a laser as the plane was coming in to land.

Yes, that's exactly what these people do. I'm not sure why you would consider that a problem.

Note once again that I'm not denying that it would be distracting or worrying.

So what on Earth are you complaining about? The whole point is that it is dangerous because it causes problems for pilots. If you agree that it's distracting, why are you arguing?

At school (more than 20 years ago) the physics department had acquired a number of red lasers. At source the beam diameter seemed to be less than 1mm, however by 15 metres the lasers projected a thin line of length .75cm to 4cm on the wall. I guess it was due to optical flaws in the source's lens. I've noticed that most cheap semiconductor lenses have some degree of divergence due to optical flaws at the interface between the laser and the air.

Again I have to wonder what your point is? You initially claimed that the beam would be so small at a distance of hundreds of metres that only a small part of the retina would be affected, yet you once again contradict that claim by pointing out that the beams diverge to a much larger size than an eye within a few metres.

I do not think the above is ever likely to be the case when the laser-operator is outside an airport perimeter and using a cheap hand-held battery-operated laser pointer and the target is a plane in motion.

Unfortunately, what you think appears to be based solely on ignorance, both on the availability of these lasers and the effects of shining one in someone's eye. Perhaps you should try doing some basic research before making claims?

[salimfadhley]

It's more serious than that. First of all, a "sufficiently powerful laser" at "sufficiently close range" can cause permanent blindness instantly, and I recall reading that it has done so in laboratory accidents. Laser weapons have been developed to do just that, see page three of this: http://www.allbusiness.com/specialty.../492548-1.html

There are lasers which can unload megajoules of energy in femtoseconds. These devices can vaporize pretty much anything in literally an instant. I know there are also hand-held battlefield lasers (mainly used as sights for pistols) which would almost certainly blind at any range, and definitely scare the bejesus out of anybody unfortunate enough to come within it's range.

You have got to be kidding. Planes do not land automatically but under manual control. And we are talking about the last few seconds of flight before landing. And suppose the pilot says to the co-pilot "what's that flickering light?" so they're both looking just when the full beam sweeps over them.

So what on Earth are you complaining about? The whole point is that it is dangerous because it causes problems for pilots. If you agree that it's distracting, why are you arguing?

My belief is that lasers can be dangerous to air travel (and almost any other kind of travel) because they are visible from a great distance (relative to other forms of light) and therefore more likely to distract or cause a nuisance. My issue was with the claims are reported in the original links: Specifically that the cheapest handheld lasers could cause actual blindness. It was that specific claim that caused even the lowest grade of pointers to be banned in Australia.

Again I have to wonder what your point is? You initially claimed that the beam would be so small at a distance of hundreds of metres that only a small part of the retina would be affected, yet you once again contradict that claim by pointing out that the beams diverge to a much larger size than an eye within a few metres.

No, you misread my previous point: I was explaining that all the cheap lasers I've ever seen show a measurable beam divergence over short distances (e.g. 15m), hence the effects of an instantaneous direct hit tends to decrease with distance more than you might expect. As the beam spreads it makes it easier to get a hit, but the power per unit-area is less, so it's less likely to actually damage or dazzle.

Matt:

That all the power of the light is concentrated at one frequency may mean that parts of the retina sensitive to that frequency may be damaged before the blink reflex (which depends upon the total power across the visible range)

I remember reading that some of the most dangerous kinds of lasers operate in frequencies which are invisible to the human eye. UV lasers are valued for their ability to rapidly cauterize flesh. I believe that older laser printers used infra-red lasers. These are particularly dangerous at close range since it may take some time and considerable exposure before the victim notices that their eyes have been permanently damaged.

We consider that being hit by lightning is a rare occurence. But there are so many lightning storms and so many people that even with the low probability of any particular individual being hit it stall happens to an average of half a dozen people a day.

I have actually been struck by lightning. I was 15 years old and climbing the Breckon Beacons wearing a steel-framed rucksack. Three people in the group I was travelling with received injuries, including myself. One required CPR but made a full recovery. I got away with burns. Amongst my belongings were a small calor gas cylinder which exploded (but bizarrely did not detonate). My rucksack was torn to shreds as were the denim jeans I wore. I spent the next 3 weeks in a Welsh burns unit. I will gladly provide extensive details of the above to anybody who attends a London #SITP event. :-)

I personally think of it as being of the same kind of magnitude of offence as throwing stones at trains. It may be that it is unlikely to cause an accident but it's a bloody stupid thing to do anyway.

I agree with this.

Tony:

Is that not enough for you? Or do you want to see a plane crash before you'll be convinced that there's a genuine risk

No, however if there were plenty of aviation authority reports that laser pointers caused actual blinding due to a direct hit to the pupil I'd be convinced. With help from pilots I've found credible reports can cause distraction (because of the visible beams).

Now jumping down the throat of some teenagers looking for kicks based on what the military have produced and might become available to terrorists, looks like an example of bullying those you can because of generic unfocused fear.

Pebble, I agree with this. The journalists have an interest to sex up the article, so they take a nugget of fact and then embellish it beyond what is credible. In this case the original article combines two classic fear-factors: The mention of eBay (fear of the scary internet), and the mention of lasers (vaguely complicated sciency things). It reminded me of panic stories about "facebook stalkers" which usually fail to mention that there were stalkers long before the Internet.

[Tony Williams]

No, however if there were plenty of aviation authority reports that laser pointers caused actual blinding due to a direct hit to the pupil I'd be convinced. With help from pilots I've found credible reports can cause distraction (because of the visible beams).

You seem to be posing a false choice between the two extremes of "blindness" (implying permanent major eye damage) and "distraction (because of the visible beams)". The truth seems to be somewhere in between: a dazzling effect which can affect the pilot's vision for a few seconds, especially at night, and at a crucial moment. That is a serious matter, and deserves to be treated as such.

[Cuddles]

My issue was with the claims are reported in the original links: Specifically that the cheapest handheld lasers could cause actual blindness. It was that specific claim that caused even the lowest grade of pointers to be banned in Australia.

Then it appears that your understanding is at fault. The article you linked made no claim about permanent blinding, it said "the beam can light-up the cockpit and blind the pilot with a dazzling flash". Which is obviously true. Again, I will point out the example of reflecting light off a watch into someone's eye. That can easily dazzle them and make them unable to see or concentrate properly, why do you think a laser pointer would be so much less effective?

No, however if there were plenty of aviation authority reports

The article you linked in the OP refers to hundreds of aviation authority reports, and explicitly quotes the pilots themselves saying how bad the effects were. Did you even bother to read it before complaining here?

[tolman]

A laser pointer, even a stronger green one of 30/50/100mW energy output isn't going to light up the cockpit of an aircraft like it was daytime, but could potentially put a reasonable amount of light in there.

The subjective brightness of a 100mW the beam is going to be of the same order as a white light of ~300mW energy, which in turn equates to a average decent LED torch at something like a 1Watt/100lumen output*, though if the beam has spread wider then the window, not all the output will get inside.
If the cockpit was otherwise dark, you probably wouldn't want someone in there playing with any kind of unnecessary light, though in daytime, any cockpit lighting effects would seem to be negligible.

When it comes to being dazzled, presumably that's a combination of relatively low-level general glare from light scattering off the windscreen and the very bright point that comes from looking into the beam itself.
While that latter effect might only dazzle a small area of the retina, if it's the important bit in the middle (such as if someone instinctively looks towards the beam), that can make it very hard doing things like reading text, and even if someone looks away, if they're trying to land at the time they can't easily do that while looking at their feet.

It would certainly be interesting knowing just how good any of the cheap lasers were at sustaining a tight beam.
It'd also be interesting to know what the temporary effects were of a beam that wasn't actually bright enough to cause permanent damage. My own experience doesn't go beyond frequent short-term dazzling from regular hiigh-power LEDs while aligning them in optics and generally experimenting, and they're obviously much less of a point source, normally being at least 1mmx1mm

(* green light of a given power is roughly 3x 'brighter' than an equivalent amount of white light, and good modern LEDs operate at something like 30% efficiency)

[Harryprice]

While that latter effect might only dazzle a small area of the retina, if it's the important bit in the middle (such as if someone instinctively looks towards the beam), that can make it very hard doing things like reading text, and even if someone looks away, if they're trying to land at the time they can't easily do that while looking at their feet.

You're talking about the fovea. But won't saccades make hitting the fovea incredibly unlikely? In the interests of science I deliberately dazzled myself just now. Though I had an after-image, I could still read OK so the fovea couldn't have been hit. For night vision, the fovea is actually a blind spot because its densely packed cones are useless (the best views of an object in low light are a few degrees off centre). A brief bright flash (like a flash photo being taken) can certainly mess up night vision for several minutes - I think that is more of a concern.

[tolman]

Why bother with all that dangerous mucking about with easily discovered explosives when all you need t do is shine a light at an aircraft and watch it tumble helplessly from the sky? If that were true then the military would never bother with conventional anti-aircraft weapons.

That'd be a rather dumb way to attack military aircraft, since some have laser countermeasures, designed in the first instance to defend against laser-sighted weapons.
If anything, the military might quite like to have some of the 'bad guys' waving laser pointers in their direction.

As for enforcement against reguar civilians playing with lasers, it may well be that the current reaction is being a bit cautious, but then that's presumably what most people would want when it comes to aircraft.

There's no obvious reason for people to play with lasers that way, so if there's even a minimal risk of distraction, it seems worth stamping out where possible. If people aren't allowed to talk to a bus driver because it might distract them, having flickering light over a windshield of an aircraft trying to land probably counts as rather more distracting.

If someone really wanted to see if they could hit a plane with their laser toy, if they had more than a handful of brain cells, they could always try pointing it at a plane that's flying away from them.

[Pebble]

If someone really wanted to see if they could hit a plane with their laser toy, if they had more than a handful of brain cells, they could always try pointing it at a plane that's flying away from them.

Never been a teenage boy? That would be no fun at all, risk is the point not skill. Immortality is not just something that teenagers possess, it applies to those they interact with as well. For some this belief persists even after hurting themselves or others quite badly.

[tolman]

Never been a teenage boy? That would be no fun at all, risk is the point not skill.

IIRC, the risky things I did were generally ones where only I was likely to get hurt.

[Montag]

Wow my first post!!

Happened late last year.

http://www.thisisplymouth.co.uk/news...l/article.html

Being very simplistic and a Physics teacher:

I use lasers in class and I have to say some of the newer cheapo lasers are very bright and focussed. When calculating the wavelength of light using a grating the kids have been getting better results than the desk top laser. We bought a class set of pointers and the focus is generally much tighter over a classroom length.

I've been flashed and have found it painfull and leaves an after image.

The green lasers we use are brighter.

I would agree that a quick flash from any of these bad boys would not 'blind' you but I could see it definitely dazzling you enough to cause an accident. A plane on approach at night and the pilot loosing all night vision... I suppose the question is: would you like to risk being in the plane when that happened?

Couldn't see it happening to a military plane or big jet but on a small single pilot 4 seater? Plausible I'd say