really invisible laser

[dag]

Hi, for a magic trick, I will pop balloons from 10 to 15 meter away with the power of my mind. (my assistent from backstage with a laser can help also)
I have some questions about popping balloons.
I read that 100 - 200 mW will pop balloons at a distance almost instantly.
Can someone confirm that?

Then there is the question of safety. I think it is an extremely bad idea to shoot 200 mW laser beams over the head of the audience to balloons that are hanging above their heads. I read that with wavelengths <400 nm and >1200 nm. the eye will filter the EMR so the eye will not be damaged as a beam wanders in ones eyes. Can someone confirm that?

Is it possible to build a 200 mW laser with 350 nm or 1250 nm ?
If so I will have a completely invisible, safe balloon popper (and a lot of mind power). What would be the price for such a device?

Hope to get some answers.
kind regards Dag

 

[bdgreenb]

first and foremost safety is the name of the game when dealing with "invisible" wavelengths. Get a green with the equivalent power to you finished product so you understand just how powerful a balloon popping laser is.

Safety talk complete, you will most likely be in the market for a IR diode or NIR diode. I have a one watt 808nm that produces slightly any light to me(and is invisible to a few people i know), to be sure you probably want to get a 980nm laser. Just keep in mind that if anyone tries to take a picture of it with an iPhone the illusion will be ruined as those cameras pick up IR light... although its very possible they will think they have captured an image of your "Mind Power"

 

[Laserbeamk]

Go with 405nm, it's great for burning. Also if you might want to also try gas lasers. They are certainly invisible.

 

[alf638]

Firstly, lasers of ANY wavelength/colour can potentially cause eye damage if their power exceeds 5mW, and wavelengths less than 400nm or greater than 1200nm WILL still damage eyes.

In the case of wavelengths less than 400nm the damage will be considerably greater than that from a visible laser, as this is the ultraviolet portion of the spectrum (the same light which causes skin cancer from over-exposure to sunlight).

Light over around 900nm is in the infrared region of the spectrum, and while invisible, definitely CAN cause damage to the eyes and again, as with UV is considerably more dangerous that visible light. As you can't see infrared light, your blink reflex won't help minimise exposure if the beam enters your eye. Rather than seeing a bright flash, blinking, and turning away, thus minimising retinal damage, the first sign that you've messed up will be your vision simply disappearing in the parts of your eye the laser hits, as your retina is burned, perhaps irreparably.

What you were likely thinking of in regards to the eye "filtering", infrared light was the fact that, to long wave infrared light (around 10um which is equal to 10000nm), many materials which are transparent to visible light, like glass and the lens of your eye, are no longer transparent. Rather than passing through these materials, the light is absorbed. This means that rather than instantly punching a hole in your retina and blinding you, such lasers would take some time, as before reaching your retina, they'd need to vaporize the lens of your eye (so maybe not INSTANT blindness, but searing pain followed by eventual blindness). Light in this area of the spectrum is only really available through the use of carbon dioxide gas lasers (10.6um). A LOW powered CO2 laser easily puts out 20-40W, enough to set virtually anything on fire, and cause a glowing white hot spot on any surface the light is allowed to fall on. On top of that, the lasers are large and heavy and run off around 18,000V DC, not something I'd recommend.

Any UV laser small enough to be used in such a show would be well out of your price range($1000s), not to mention the fluorescence UV light causes in materials. Have you ever seen white materials glow under a "black-light"? That's an example of what happens when low energy low intensity UV interacts with a fluorescent surface. High energy high intensity UV like that of a laser would cause FAR more fluorescence, so even though the light itself is invisible, you could still see where and what the laser was doing.
The only somewhat commonly available UV laser is a nitrogen gas laser, which emits 337.1nm, but even then, it's a pulsed laser and has average outputs too low to do what you describe.

High power infrared lasers are more commonly available, have a read about 808nm diode bars (slightly visible to some people), and pulsed solid state Nd:YAG lasers if you're interested, but again these can all cause severe and permanent eye damage.

200mW can pop a balloon at close range if held still for a few seconds, to easily pop a balloon unfocused at several metres without a tripod you'd need considerably more power, which I wouldn't recommend, as even 200mW can cause permanent eye damage.

The only way this would be even remotely safe was if every person in the audience had a good quality pair of laser safety glasses rated for the wavelength being used.

I'm sorry if I sound a little harsh, I'm not trying to dissuade you just for the sake of it, but with this kind of thing there's a very real chance of serious eye damage.

Go with 405nm, it's great for burning. Also if you might want to also try gas lasers. They are certainly invisible.

405nm isn't invisible, it's violet, and only some gas lasers (Nitrogen CO2), are invisible, Argon, Helium-Neon, Argon/Krypton Copper Vapour etc. are all visible, as are many more.

 

[TaterMay]

Go with 405nm, it's great for burning. Also if you might want to also try gas lasers. They are certainly invisible.

Don't go with 405nm. Unless you want your audience to laugh at your poorly executed magic tricks, as they will see a purple dot popping all of your balloons. I would recommend an IR build, maybe the type that pumps the 532nm DPSS lasers, but we need some more advice from someone else, as I've never had any reason to use one. It could be as simple as popping out the crystals that emit the 532nm green wavelength, but I can't confirm this.

Someone else correct me if I'm wrong, but I believe the invisible beams are going to be the most dangerous, as the eyes will not see anything, and therefore will not do anything to protect themselves. I'm not sure exactly how you could do this safely, honestly.

 

[jeffreythe00]

I think you are all thinking about it too much. Heres the way I see it. When you're doing a magic show for a crowd of people, isn't there usually several people who record the event with their camera?

In case some of you guys don't know, cameras are a lot better at seeing IR light than we can with our naked eye. So if you use a diode you're probably going to be in the 700-1500nm range. Well within what most cameras can see.

I personally don't think using a "hidden" high powered laser is a good idea in front of a crowd. Theres too many liability issues to consider for me to consider it safe. It screams lawsuit to me.

So yeah, great idea in concept but as far as practicality and safety goes I think you can find better ways to "pop a balloon with your mind". Technology has come a long way so perhaps you can use some sort of wireless electronic ignitor.

Good luck with your shows!

 

[alf638]

Don't go with 405nm. Unless you want your audience to laugh at your poorly executed magic tricks, as they will see a purple dot popping all of your balloons. I would recommend an IR build, maybe the type that pumps the 532nm DPSS lasers, but we need some more advice from someone else, as I've never had any reason to use one. It could be as simple as popping out the crystals that emit the 532nm green wavelength, but I can't confirm this.

Someone else correct me if I'm wrong, but I believe the invisible beams are going to be the most dangerous, as the eyes will not see anything, and therefore will not do anything to protect themselves. I'm not sure exactly how you could do this safely, honestly.

Invisible beams will definitely be the most dangerous, as I said, they won't activate the blink reflex, so you won't naturally blink and minimise exposure, the first indication you'll get that somethings gone wrong is when you start to lose vision in the areas of your eye the beam is hitting.
532nm lasers use an 808nm pump diode (faintly visible to most people), which stimulates a Nd:YAG or Nd:YVO4 crystal to itself lase at 1064nm (completely invisible), this 1064nm light is then frequency doubled by a KTP crystal to the 532nm green we know and love.
If you just took out the crystals from a 532nm pointer you'd have a very divergent 808nm beam as the Nd:YVO4 and KTP are normally glued together in to an individual crystal. There would be no lens to focus the raw output of the pump diode, which is also usually multi-mode and thus has awful divergence, so you'd end up with something incapable of burning at a distance, but more than capable of damaging eyes close up, plus it would be faintly visible.

 

[RedCowboy]

I would think you would want to be outside of the visible and near IR spectrum. Something more like a small C02 in the 10400nm range maybe at a 1/4 watt, but I would avoid near IR, I have seen 3-5 watt handhelds like that but they are an accident waiting to happen, you or your assistant could easily be forever blinded just putting in the batteries.

 

[marcuspeh]

You shouldn't think about using lasers in the first place. Unless all you audience and your crew will be wearing safety goggles, this would result in someone getting blind. Besides, you will need a laser more than 5mw and most countries made laser above 5mw illegal. You can always find better ways to "pop a balloon with your mind". Technology has developed a lot so perhaps you can use some sort of wireless electronic ignitor. Remember, no matter what you do, DO NOT USE A LASER

 

[RedCowboy]

You shouldn't think about using lasers in the first place. Unless all you audience and your crew will be wearing safety goggles, this would result in someone getting blind. Besides, you will need a laser more than 5mw and most countries made laser above 5mw illegal. You can always find better ways to "pop a balloon with your mind". Technology has developed a lot so perhaps you can use some sort of wireless electronic ignitor. Remember, no matter what you do, DO NOT USE A LASER

I agree, marcuspeh is right.
Not to mention you need a license to use a laser in a public display and you set yourself up for all kinds of liability.

 

[dag]

Read on a website of VUB (Brussels university) (my translation)

The eye is protected by the cornea.
Light with a wavelength between 400 nm and 1400 nm will enter the eye through the cornea and is focused by the lens on to the retina. If lambda <400 nm or lambda >1400, the cornea will block the radiation. The transmission curve of the retina in function of the wavelength is given beneath.
https://www.vub.ac.be/preventie/Images/Lasers_Transmissie.JPG

I mis-concluded that lasers outside the 400 - 1400 spectrum were harmless to the eye and that skin could take much more.
Also if the time to pop a balloon is extremely short, the probability to have an accident is not that big.

Anyway, I've got the message of what most of you were telling.
Don't mess with lasers as they could take your eyes and the eyes of everyone around you.
Except if someone has ideas on how to perform it in a safe way, I will kill the trick
I thought a DMX controllable device that high above the floor, shoots helium balloons at lets say 3 m height would be OK.

Maybe look at static electricity, also a very fun tech :yh:

 

[GatoX]

Don't burn the cornea doesn't means don't burn the retina. Static electricity could be awesome if the people doesn't see the spark. Heating it with a small cable (near invisible) could pop the balloon without laser damaged people