# Are laser pointers dangerous? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [November 24, 2000, 11:14am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524 "2000-11-24T11:14:24Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Jamoross](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jamoross/32/3241_2.png) [@Jamoross](https://boards.straightdope.com/u/Jamoross)\ **Post date:** [November 24, 2000, 11:14am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/1 "2000-11-24T11:14:24Z")
So here’s this Staff Report on the relative hazards of [laser pointers](http://www.straightdope.com/mailbag/mlaserpoint.html) and I think to myself that this is right up my alley, so I’d better go jump into the discussion and help dispel any ignorance that might creep in and, lo, there is **no** comment thread yet. Well, the Report was fairly thorough and free from errors so maybe nobody has anything more to say. Bah! I want this subject discussed, dammit! The first time since Ed mis-edited The Great One’s column on package recycling --making it ever so slightly dubious-- that I have any expertise to contribute and nobody has even opened a thread. I’ll just do it myself then… There! I even figured out how to include a link to the relevant Staff Report. (I’d have done the same for the recycling column but the archive search function returned an “internal error”. Something about “chunked content”.) - jam ---
**Author:** ![monkeylucifer](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@monkeylucifer](https://boards.straightdope.com/u/monkeylucifer)\ **Post date:** [November 24, 2000, 5:07pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/2 "2000-11-24T17:07:49Z")
Well, the article forgot to mention the possibility of the owner of said laser getting pumelled by an angry mob of people annoyed with childish behavior. I absolutely **HATE** being in a movie and having some lord of the jack-asses beaming his little toy onto the screen. Show some consideration you moron. (sorry for the slight hi-jack…but it had to be said) ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [November 24, 2000, 5:48pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/3 "2000-11-24T17:48:09Z")
Personally, I am extremely thankful that the general public thinks laser pointers are dangerous, because the Better Half was once able to use that factoid to remove from circulation a group of high school wrestlers who were in the bad habit of harassing parents dropping off Midget Wrestlers at practice. On this particular occasion they were shining a laser pointer at people driving up in their cars, and it took him about 2 minutes to have the coach explain to them that they were supposed to leave after practice, not hang around. Up till that point, the coach had been like, “Oh, well, they’re not hurting anything, HEY, GUYS, YOU KNOW YOU’RE SUPPOSED TO GO HOME AFTER PRACTICE [shrug]”. So vive la ignorance, eh? ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [November 24, 2000, 5:57pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/4 "2000-11-24T17:57:14Z")
BTW, **Jamoross,** you didn’t say what your expertise is, exactly? Manufacturer of laser pointers? Repair of same? Chairperson of appropriate Congressional Sub-Committee investigating inappropriate appropriation of funds for appropriately equipping Operation Desert Storm commandos for the invasion of Kuwaiti movie theaters? ---
**Author:** ![Jamoross](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jamoross/32/3241_2.png) [@Jamoross](https://boards.straightdope.com/u/Jamoross)\ **Post date:** [November 25, 2000, 5:49am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/5 "2000-11-25T05:49:44Z")
Oh, I’m an optical systems engineer. I am also a designated laser safety officer. Well, I was when I was in the U.S. Here in Japan that kind of thing is much less formalized and is basically voluntary. It’s the same job, just without the fancy titles. Anyway, I’m Senior Engineer in a laser applications laboratory and factory. I also teach laser safety and review machine designs to insure they have the proper interlocks and other protections. - jam ---
**Author:** ![furt](https://avatars.discourse-cdn.com/v4/letter/f/439d5e/32.png) [@furt](https://boards.straightdope.com/u/furt)\ **Post date:** [November 25, 2000, 6:48am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/6 "2000-11-25T06:48:12Z")
It’s also worth pointing out that in most states it is a crime to aim a laser pointer at a police officer. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [November 25, 2000, 1:32pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/7 "2000-11-25T13:32:52Z")
Now I am interested, **Jamoross,** and seriously curious. Here’s my chance to “Ask the Expert”. Is it true that checkout clerks have to be very careful not to look down into the scanner when they beep things? I’ve never been a checkout clerk, but I think it would drive me crazy to be told “Don’t look at the red light, don’t look at the red light”. Are there documented cases where checkout clerks have been injured by looking at the red light? You teach Laser Safety? Do you go around to Wal-Marts and hold meetings, or are you training the people who train the people? Or are we just talking industrial safety here? It’s hard for me to visualize a laser pointer as an actual “laser”, as in “laser beam”, as in “Dr. Evil blowing up the world laser beam”. So the Staff Report is saying that the injury to the eye that results from having a laser pointer shined into it is simply the result of having a really bright light shined into it, the same as looking at the sun, and not from having a hole burned in the retina by a Dr. Evil-type laser beam? Well, there now, I didn’t know that. Some of us are more tech-challenged than others. I just recently found out that cars don’t have carburetors anymore (they have fuel injection). ---
**Author:** ![Stimpy](https://avatars.discourse-cdn.com/v4/letter/s/779978/32.png) [@Stimpy](https://boards.straightdope.com/u/Stimpy)\ **Post date:** [November 25, 2000, 3:35pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/8 "2000-11-25T15:35:50Z")
Laser pens are indeed banned in the UK. Whilst working at Gatwick Airport, London, I was instructed to confiscate said items if found upon the personage of people travelling into or out of the UK - my undesirable job at the time was to randomly search passengers and their luggage if flying with American carriers. I think they were originally banned when they hit the headlines back in the mid 90’s. Kids were hanging out on motorway bridges, aiming them at passing drivers, causing all kinds of fatalities apparently… ---
**Author:** ![Badge](https://avatars.discourse-cdn.com/v4/letter/b/4bbf92/32.png) [@Badge](https://boards.straightdope.com/u/Badge)\ **Post date:** [November 25, 2000, 5:29pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/9 "2000-11-25T17:29:25Z")
Washington state passed legislation last year, making certain uses of laser pointers a crime. Personally, I think it’s cool to realize we now have a law called UNLAWFUL DISCHARGE OF A LASER. Doesn’t that sound amazingly futuristic, like something from a 1950’s science fiction magazine? ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [November 26, 2000, 6:41am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/10 "2000-11-26T06:41:33Z")
I just spent about a minute shining a laser pointer into the eyes of a fly. Range was about 3 inches.I can now put my finger about 1/2 inch from the flys head and it just turns away. It must not be blind but 1/2 inch is pretty close.Kind of unscientific but I think I affected it’s sight. Don’t know if it is permanent or not. ---
**Author:** ![Jamoross](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jamoross/32/3241_2.png) [@Jamoross](https://boards.straightdope.com/u/Jamoross)\ **Post date:** [November 26, 2000, 4:39pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/11 "2000-11-26T16:39:02Z")
> [@](#): > > \*Originally posted by Duck Duck Goose \* > Is it true that checkout clerks have to be very careful not to look down into the scanner when they beep things? The warning to checkout clerks stems from the power of the lasers typically used in package scanners. There is no real danger from a supermarket scanner so long as the beam keeps moving. The “eyesafe” limits vary depending on the wavelength (color) of the beam and whether or not it is scanned. If the scanner happens to stop spinning there is a good chance the operator will look down to see what’s wrong. Personally, I doubt the admonition not to look into the beam would overcome this natural tendency. Keeping this in mind, part of the requirements for such systems is a mechanism to interrupt the beam if the scanner stops. But of course these thing can fail too, often in a way that goes unnoticed until the unit actually stops counting beer cans or whatever. > [@](#): > > You teach Laser Safety? Do you go around to Wal-Marts and hold meetings, or are you training the people who train the people? Or are we just talking industrial safety here? Listen Ducky, those nifty supermarket scanners are “industrial” in more than one sense. Not that they are especially dangerous, but they do have to be pretty tough to withstand constant banging with 2-liter bottles and the odd frozen turkey etc. I have never personally taught in a Wal Mart store. Mostly I teach repairmen, operators, and the engineers who design and build systems that incorporate lasers. > [@](#): > > So the Staff Report is saying that the injury to the eye that results from having a laser pointer shined into it is simply the result of having a really bright light shined into it, the same as looking at the sun, and not from having a hole burned in the retina by a Dr. Evil-type laser beam? Well, there now, I didn’t know that. Ahem. Stare at the Sun and you **will** burn a hole in your retina. Imagine some miscreant holding a magnifying glass between the Sun and a hapless ant. What happens to the ant? Now remember that the lens of your eye is at exactly the right distance from your retina to focus light on it. Point your personal optic imagers at Old Sol and your fovea will suffer the ant’s fate. Lasers are more dangerous than a bright light because their brightness doesn’t diminish with distance the same way ordinary light does. If someone needs their vision to survive, like the pilot of a helicopter or even a driver on the highway, then even momentarily dazzling them can be extremely dangerous. Finally, permanent eye damage with even a strong pointer (500 milliwatts or so) is very unlikely because of the natural blink reaction. Anybody with a reaction time longer than the quarter second mentioned in the Report has a serious attention disorder anyway and was probably pointing the thing at themselves. - jam ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [November 26, 2000, 8:46pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/12 "2000-11-26T20:46:02Z")
Excellent! Thank you for enlightening me. And you did such a good job on your report that you are hereby excused from taking the final. 🙂 ---
**Author:** ![cjclark](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cjclark](https://boards.straightdope.com/u/cjclark)\ **Post date:** [November 26, 2000, 11:57pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/13 "2000-11-26T23:57:35Z")
> [@](#): > > \*Originally posted by Jamoross \* > \*\* > > > [@](#): > > > > \*Originally posted by Duck Duck Goose \* > > So the Staff Report is saying that the injury to the eye that results from having a laser pointer shined into it is simply the result of having a really bright light shined into it, the same as looking at the sun, and not from having a hole burned in the retina by a Dr. Evil-type laser beam? Well, there now, I didn’t know that. > > Ahem. Stare at the Sun and you **will** burn a hole in > your retina. Imagine some miscreant holding a magnifying > glass between the Sun and a hapless ant. What happens to > the ant? Now remember that the lens of your eye is at > exactly the right distance from your retina to focus light > on it. Point your personal optic imagers at Old Sol and > your fovea will suffer the ant’s fate. Now, let no one think I am condoning staring at the sun, but this analogy is a little off. I don’t mean to nit-pick, but if we didn’t, what would the point of the message boards be? And how can we let the optical engineer spread inaccuracies about optics? When one fries an ant with a magnifying glass, you attempt to get the subject in the focal point of the magnifying glass. Now, the lens of the eye projects an image on the back of the eye. This image will always be _behind_ the focal point. As anyone who has ever tried to sizzle ants knows, if you pull the glass back from where you get a nice tight point (the focal distance) there is another point where you will get a nice sharp image of the sky projected on the area around your victim, er, subject. And the cooking power of this image is not nearly as good, but not bad either. That is how your eye works. If our lens actually focused the light on the back of our eye we’d all see one bright spot in the center of our field of view. Although we’d be much better at seeing in the dark, who cares when your vision is 10^38/20. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 27, 2000, 12:37am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/14 "2000-11-27T00:37:36Z")
Try that experiment again, **cjclark**. The sky is far enough away to be considered infinitely distant, so the image distance is exactly equal to the focal distance. The light from any given point in the scene you’re viewing is focused onto a single point on your retina: The reason that you still see a complete scene is that you’re seeng many points, each focused in a different place. The spot of light you project onto the ant won’t quite be a point, because the Sun isn’t a point of light in the sky: It’s size will be equal to the sin(30’)\*f, 30’ being the angular size of the Sun in the sky, and f being the focal length of the lens. With a single lens, you can’t get it to a single point no matter what you can do, all you can do is get the spot as small as possible, which is exactly the spot where you get a clear image of the Sun. ---
**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\ **Post date:** [November 27, 2000, 5:27pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/15 "2000-11-27T17:27:34Z")
> [@](#): > > \*Originally posted by Badge \* > Washington state passed legislation last year, making certain uses of laser pointers a crime. > > Personally, I think it’s cool to realize we now have a law called UNLAWFUL DISCHARGE OF A LASER. Doesn’t that sound amazingly futuristic, like something from a 1950’s science fiction magazine? Except that in a 1950s story the author would probably have predicted that laws against lasers would be passed in 1970 or 1980. We are woefully lagging behind the predictions of early SF authors! Instead of sounding futuristic, it sounds quaint and outdated. In the year 2000, we should be outlawing teleportation of fraternity boys into the high school girls’ locker room. ---
**Author:** ![Jamoross](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jamoross/32/3241_2.png) [@Jamoross](https://boards.straightdope.com/u/Jamoross)\ **Post date:** [November 28, 2000, 4:56am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/16 "2000-11-28T04:56:06Z")
I think the “nice sharp image of the sky” **cjclark** is talking about is more likely an image of some nearby objects like leaves on a tree or the silhouette of a phone pole. These things are, um, _substantially_ closer that the Sun. Close enough in fact to require a very noticable repositioning of a simple lens to image them instead of the Sun behind them. At such a position the Sun’s image would be slightly defocused and less intense. > [@](#): > > _By Chronos:_ > The spot of light you project onto the ant won’t quite be a point, because the Sun isn’t a point of light in the sky: It’s size will be equal to the sin(30’)\*f, 30’ being the angular size of the Sun in the sky, and f being the focal length of the lens. With a single lens, you can’t get it to a single point no matter what you can do, all you can do is get the spot as small as possible, which is exactly the spot where you get a clear image of the Sun. Actually, no sequence of lenses will yield a single point of light either. And there is another way to calculate the size of the spot you will get with a simple lens. Just multiply the diameter of the Sun by the focal length of your lens and divide by 1 AU. This ignores lens distortion (as does **Chronos** ’ method) but will be very accurate. Speaking of distortion, lens abberations are the bane of insecticidal pyrolyzers everywhere. For a really hot spot, you want a big lens with a short focal length. This would mean a pretty globular piece of glass with consequently lots of spheric distortion. Unless you use a Fresnel lens. These are usually flat plastic lenses like you sometimes see stuck on the back window of motor homes. For a few bucks you can get some nice big ones from Edmund that are plenty dangerous in sunlight. Forget the ants; you can burn holes in the **asphalt** with one of these babies. - jam ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [November 28, 2000, 2:29pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/17 "2000-11-28T14:29:40Z")
> [@](#): > > \*Originally posted by Arnold Winkelried \* > \*\* In the year 2000, we should be outlawing teleportation of fraternity boys into the high school girls’ locker room. \*\* [hijack] :eek: Arnold, this is scary–only this morning I received an e-mail from a friend, warning me about THIS VERY THING!! Yes, it seems that fraternity boys at Northwestern in Evanston are using equipment from the National Accelerator Laboratory to beam themselves into the girls’ locker room at Sacred Heart High School in Naperville. Parents are furious, and are calling for legislation to outlaw this. Please, please, contact your members of Congress, and forward this e-mail to everyone you know. [/hijack] We now return you to your regularly scheduled Real World. ---
**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\ **Post date:** [November 28, 2000, 5:54pm UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/18 "2000-11-28T17:54:20Z")
I knew it! Will science always be turned to evil uses by the criminal mind? ☹ ---
**Author:** ![Jamoross](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jamoross/32/3241_2.png) [@Jamoross](https://boards.straightdope.com/u/Jamoross)\ **Post date:** [November 29, 2000, 8:01am UTC](https://boards.straightdope.com/t/are-laser-pointers-dangerous/42524/19 "2000-11-29T08:01:43Z")
"EVANSTON- In a bizarre demonstration of collegiate ingenunity, several students from the McCormick School of Engineering and Applied Science at local Northwestern University allegedly invaded a high-energy laser facility at the Fermi National Accelerator Laboratory in nearby Bativia over the weekend. The boys turned the lasers on themselves in what was initially thought to be a desperate escape attempt. Investigators now believe that the boys had purposefully planned the entire incident to ‘beam’ themselves to a high school in Wheaton five miles away. "Powerful light beams were used to separate and analyze the atomic structure of their bodies. Laboratory Director Michael S. Witherell explains: ‘The three young men were disintegrated and at first we thought they had died, you know, like ants under a really big magnifying glass. Then a researcher noticed that one of our particle accelerators had also been tampered with and was still active. That’s when we decided they may have actually escaped.’ "But that wasn’t the whole story. Their destination was St. Francis High School on Roosevelt Road in Wheaton where a girl’s basketball tournament was in progress. Amidst dozens of girls in various states of undress, the boys materialized near the shower area in the girl’s locker room. According to a coach of one of the visiting teams, many girls were startled or became upset but none of them realized how the invaders had accomplished their entry. ‘I thought they just sneaked in or had been hiding’ said one girl whose name was not released. Said another, ‘Somebody yelled so I looked around and they were right there’. “An individual claiming to be a friend of the boys and asking that his name be withheld said the whole idea came about while playing with a handheld laser pointer more than two years ago. The pointers have recently been banned from area high schools.” - jam ;)/