Tips when Using Laser Pointers Safely
We have known some FAQ about laser pointer, today, there are more laser pointer FAQ to share with you. This article will tell you laser pointer hazards, safe use in night sky and the control measure.
LASER POINTER HAZARDS
What is the biggest problem with laser pointer misuse?
The most serious problem by far comes when laser pointers are aimed towards aircraft. People have been arrested and even jailed for shining lasers towards planes and helicopters. (See the News page for many articles about this.) So don’t do it!
Why is a laser pointer hazardous to aircraft?
We see three statements all the time, on Internet message boards and on comments to news stories about incidents. People say that the dot from a laser pointer is small, which is hard to hit or keep it on an aircraft, and that an aircraft’s windows are facing up and thus away from the ground. While there is some truth in these statements, the fact is that laser light can all too easily be a distraction or obstruction to pilot vision:
Beam size: A laser’s beam spreads out. At long ranges the beam can be many inches or even feet in diameter. When laser light hits an aircraft’s windscreen, tiny scratches and dirt spread the light out even more, causing glare around the beam center. The result is that pilots do not see a small dot, they see a large glow similar to being in a flashlight or searchlight beam. It can be difficult or impossible to see through the glow. You can see this in photos here and here.
Beam flashes: Yes, it is hard to hand-hold a laser on a moving target that is far away. That’s why in most laser pointer incidents, pilots don’t see a steady light on them. Instead, they see one or more flashes. The flashes are distracting at best, and at worse, they can be bright enough to cause temporary flash blindness. This is similar to having a camera flash (or flashes) goes off in your face. Even if the beam is just waved around the aircraft so it does not directly enter the windscreen, it can be distracting or worrisome to see a waving beam aimed towards one’s aircraft. (See the video here, where the laser only occasionally hits the helicopter but the beam still is a distraction.)
Window orientation: If a pilot can see the ground outside his or her window, then obviously the pilot could be directly hit by a laser aimed from anywhere within that view. Plus, even if the pilot’s eyes are not in a direct line with the laser source, the laser beam could light up other areas in the cockpit such as the ceiling, causing a distraction. This is because, as discussed above, the light at altitude creates a large glow on the windscreen.
So, when thinking about risks from laser light, don’t think just about airplanes flying at 35,000 feet directly above you. Think about the times airplanes are at most risk: during takeoffs and especially during landings. And think about helicopters, which fly low and slow and have large bubble canopies. That’s why almost all laser pointer aircraft incidents involve airplane landings, takeoffs, and helicopter operations.
What other laser pointer problems are there?
Laser pointers have been aimed at cars and trucks. Just as with aircraft, this can distract or temporarily blind a driver — obviously unsafe.
At sporting events, spectators have aimed laser pointers at players such as football goalies. This is unsportsmanlike (to say the least!) as well as a potential eye hazard for the player.
At concerts and movie theaters, sometimes an audience member will think it is funny to wave the laser dot around on the stage or screen.
Such misuse will backfire. When ordinary citizens are distracted, or annoyed, or temporarily blinded, they are more inclined to support restrictions or bans on laser pointers.
But a laser pointer is much safer than a (knife, gun, etc.)!
It is true that a laser pointer’s beam causes much less direct damage to humans than a knife or gun. Only a handful of people have had eye injuries caused by laser pointers wielded by irresponsible users.
However, the potential for serious harm is primarily due to bright-light distractions and flashblindings. If a pilot or the driver of a vehicle is distracted or temporarily flashblinded, the laser could cause significant damage to property and/or persons.
In most cases, a laser flash is manageable by pilots. However, aircraft accidents usually occur due to a string of events, any one of which would normally be manageable but as a group lead to disaster. If during a tricky landing or an emergency the pilots are distracted or flashblinded, the laser flash could be the “straw that broke the camel’s back”.
For example, think about US Airways flight 1549, the one that landed safely in the Hudson River in January 2009. The pilot showed great skill. But imagine if someone on land saw the plane coming in and used his laser pen to point it out to a friend. If the pilots were flashblinded or even just distracted by laser light, there could have been a very different outcome.
When does a laser pointer get powerful enough to be dangerous?
There is no specific threshold between a “safe” laser beam, a potentially hazardous one, and a clearly dangerous beam. The following are some guidelines.
Bright Light Hazard
Even a “legal” (in the U.S.) 5 milliwatt laser pointer can be a potential hazard if the light distracts or temporarily flashblinds a person such as a pilot. This is why you NEVER aim a laser pointer at an aircraft, or the driver of a vehicle.
For direct damage to the eye, the exact severity will be due to many factors: beam power, exposure time, beam/eye relative motion, distance from the laser, and retinal injury location.
If a person deliberately stares into a laser, even a small 1 milliwatt beam could cause a spot on the retina.
Fortunately, the eye’s natural “blink reflex” causes a person to involuntarily blink and/or turn away from a bright light. Taking this into account, an accidental exposure to a 5 milliwatt beam is considered acceptable, as long as the person is not overriding their blink reflex.
After some point, even blinking and moving isn’t fast enough to prevent injury. As a very rough approximation for laser pointer use, above 50 milliwatts the potential hazard from general use outweighs the benefit of a brighter beam.
At around 500 milliwatts (1/2 watt), an accidental exposure at close range will almost definitely cause eye injury. The victim may or may not notice it depending on where the spot is on the retina.
At around 200-300 milliwatts, the beam from a laser can be felt on the skin, depending on the beam focus, skin color (absorption), etc. At roughly 500 milliwatts, the laser’s beam begins to be a skin burn hazard if the person is within a few meters of the beam.
Incidentally, even powerful industrial lasers cannot cause deep burns, severed limbs, gun-type injuries or other effects seen in sci-fi movies. While multi-watt laser beams are definitely serious eye hazards, they are ineffective at causing incapacitating body injuries.
On a CSI:Miami episode, a laser pointer brought down a plane by injuring the pilots’ eyes about 2 miles away. Is this possible?
The CSI:Miami scenario is not plausible. A legal, off-the-shelf laser pointer like the one on the show has a maximum power of 5 mW. A beam from this laser is a distraction to pilots out to about 2.2 miles. However, the light level would not cause veiling glare, flashblindness or (especially) eye injuries. The producers and researchers for CSI:Miami took a lot of dramatic liberties in this case! (The episode is “Money Plane”, first aired March 7, 2005.)
SAFE USE IN THE NIGHT SKY
Why should laser pointers never be aimed at aircraft?
It is bad for pilots and passengers, it is bad for you (arrest, trial, jail) and it could lead to bans on laser pointers. See this page for more details.
But isn’t it legal to illuminate aircraft if the laser power is low enough?
People have been arrested and brought to trial for hitting an aircraft with laser light that is theoretically below FAA-specified power levels. A California man was jailed for two years, for using a legal 3.3 milliwatt laser pointer on an aircraft. He was jailed even though the irradiance may theoretically have been OK according to the FAA.
Any deliberate targeting of an aircraft is taken very seriously by pilots and authorities. They don’t have power meters. All they know is that someone aimed a laser at them — and it could even be a laser sight on a gun. Therefore, if found, you will almost certainly be arrested.
Doesn’t the beam of a laser pointer aimed outside seem to end?
If you aim a laser pointer into a clear nighttime sky, it can appear that the beam ends after a certain point. This is a visual effect similar to an optical illusion. Unfortunately, someone could mistakenly think the beam only goes a few hundred feet and then stops. They might aim it at a plane thinking that the beam can’t “go all the way” to the aircraft.
This is a dangerous misconception. The laser’s light does not suddenly stop in mid-air. It spreads out and gets dimmer, but still can be bright for many miles. For example, a 5 mW green laser pointer – which is legal in the U.S. — is a distraction hazard to pilots 2 miles away; a 125 mW pointer can cause distraction over 11 miles away.
This explains why you should NEVER aim a laser at or near an aircraft: If you can see the aircraft or its lights, then it can certainly see your laser — and be visually distracted or flashblinded by it.
Why are pilots bothered by laser light that doesn’t bother me?
Pilots are not laser enthusiasts. They are flying an aircraft and are dark-adapted; they do not expect or want bright lights flashed in their face. This is especially true during times they have to concentrate, such as takeoff, landing, and any out-of-the-ordinary situations. A bright flash seconds from a critical operation is not a good situation. This is why you should NEVER aim a laser at an aircraft.
What about non-laser sources like searchlights? Are they a hazard to aviation?
Tests conducted by Dutch researchers have shown that searchlights are much less distracting than lasers. For example, the beam from a truck-mounted searchlight did not significantly distract or impair a helicopter pilot flying 200 to 500 meters away. In contrast, the beam from a 3.5mW laser pointer purchased at RadioShack caused distraction, startle, glare and even some flashblindness/afterimages at the same distance.
Aircraft can look like stars. What is the best way to point out stars in the night sky?
A slow-moving, far-away aircraft can look like a star. If you are doing astronomy pointing at a “star talk”, use the laser pointer to circle unknown or faint objects. Don’t point directly at them unless you are sure it is a star (i.e., Orion’s belt or the Big Dipper handle). For more information on star pointing applications, see this page.
I want to make my own laser to burn things. Is this dangerous?
Yes, you need to know about the potential dangers before deciding to build such a laser. These include obvious hazards such as too much visible light, and non-obvious hazards, such as the possibility of too much invisible (infrared) light. For much more information, visit the DVD flashlight hack safety warning page.
Is a laser pointer ban effective?
Banning or severely restricting laser pointers seems like a simple, attractive solution to misuse such as pointing at aircraft. However, there are a number of problems:
It is hard to effectively define laser pointers. To give one example, if “battery powered” lasers are banned, it still is relatively easy to find AC outlets in public spaces, or to use a $20 inverter to run a laser off a car’s 12-volt power socket.
It is hard to enforce. In a world with Internet sales by mail, and easy world travel, it becomes difficult to check every package or person at Customs to see if they have a laser pointer.
It does not stop someone who really wants a laser. It is easy to get new or used lasers, either by themselves or built into equipment. Even DVD and Blu-Ray players contain powerful laser diodes. If hobbyists can get these, so can anyone with evil intent. Said another way, “When laser pointers are outlawed, only outlaws will have laser pointers.”
It stops legitimate use of laser pointers by teachers, business people, astronomy educators and others who find a laser ideal for pointing out objects.
“It is like banning the kitchen knife because we have people using the knives incorrectly,” according to Professor Hans Bachor, president of the Australian Optical Society, as quoted by the Australian Broadcasting Corporation.
Here is an example of how bans may not work: In the Australian state of Victoria, lasers are regulated as a controlled weapon. A permit is required to buy a laser. Yet on April 6 2008, the Sunday Herald Sun of Melbourne reported that “one young shopper – without a permit – was able to buy six lasers, from six separate outlets in less than an hour…. for as little as $3.”
It is unclear whether a laser pointer ban significantly reduces laser incidents. It is certain that anyone who wants to deliberately use a laser for bad purposes can easily do so, ban or no ban.
For an interesting perspective, see this online debate about banning laser pointers. Note that there are some inaccuracies or misconceptions in the material so do not rely completely on the arguments and data in this online debate.
Would it work to make the windshield mirrored, like sunglasses?
No, a mirrored aircraft windscreen, or helicopter “bubble”, would not be practical. First, there are cost and durability issues regarding the mirror coating. But more importantly, a mirrored coating would reflect ALL light going through it. If it dims a laser beam by 90%, so it can be safely viewed without glare, it also dims all other lights by 90%. This includes airport runway lights, guide beacons, warning strobes etc. These are already dim to begin with — it would be like landing an airplane with dark sunglasses on.
Some smart person might say “Make the mirror coating reflect only green laser light”. However, the basic problem is still the same. In this case, green lights dim out or disappear. Also, not all incidents involve green lasers. Some people have been jailed in the U.S. for using a red laser against an aircraft.
It is true that for military uses in combat, there are some ways to protect pilot vision from laser attacks. But for civil aviation, things such as active goggles, LCD windscreens, mirror coatings, etc. are not practical responses. They are expensive and have significant limitations.
You can bet that if pilots, airlines, and the public get fed up with laser incidents, they won’t be paying for advanced anti-laser technology. They will just call for a ban on laser pointers, as has already been done in Australia and elsewhere. A government ban makes the public feel as if something is being done. (Whether such a ban will prevent laser incidents is of course a different question.)
That is why it is better to try to inform laser pointer users to NEVER aim at or near an aircraft.
Why don’t pilots wear goggles?
There are many reasons goggles aren’t practical. Here are a few of the major ones:
A laser exposure on a pilot is usually short and surprising; the incident would be over before goggles could be donned.
The alternative is to routinely wear laser-protective goggles, at least during take off and landing for fixed-wing airplanes. Helicopter pilots would have to wear them all the time. As you might imagine, pilots would strenuously object to doing this.
Goggles by their nature dim or block selected wavelengths (colors) of light. Pilots could not see all colors on their instrument panels and CRT/LCD screens, and their night vision would be reduced.
Goggles would have to protect against a wide range of potential wavelengths and brightness. This is not practical in a standard goggle which is usually optimized for one or a few wavelengths within a known power level (e.g., fixed optical density).
Active goggles are under development but the cost and effectiveness for civil pilots would not make this practical for routine wear (they might protect military pilots in a war zone).
According to an FAA official, as of December 2008 there are no commercial transport aircraft using anti-laser measures such as goggles, windscreen filters, or the Optra Laser Event Recorder.
If regulators are asked to choose between pilots saying “ban laser pointers” and laser pointer users saying “wear goggles on every flight”, the pilots are going to win. For those who like laser pointers, the best solution is to get the word out to all enthusiasts: NEVER aim a laser at an aircraft.
The above laser pointer FAQ comes from LaserPointerSafety.com.
|Print article||This entry was posted by lang on July 23, 2010 at 3:41 am, and is filed under Laser Pointer. Follow any responses to this post through RSS 2.0. You can leave a response or trackback from your own site.|
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