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Laser tag safety and laser distance

HeroicO

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Hi everyone I'm new here. I did a quick search and didn't see anything on laser tag, but if I missed something or am in the wrong place please let me know :)

I'm trying to develop a custom laser tag for me and my friends. Currently the way I am making it is through an IR LED, IR Sensor, and an Arduino. Here are the links:


The problem is the range. With a 20 degree beam width, the LED doesn't work further than a couple feet, and it requires extreme accuracy. As a result, I am coming here to ask if lasers would be the answer. I was thinking of using a 5mW 940nm IR laser pointer with a lens to spread the beam slightly.

I read the stickied thread all about laser safety and how it requires glasses, but I don't understand. How do laser tag facilities operate without laser safety glasses? The one I've been to doesn't require any protective eyewear.

Would the fact that I am spreading the beam using a lens make it less dangerous to the eye?

Keep in mind we're a bunch of high schoolers so if I'm in over my head here, please let me know. None of them are stupid enough to stare into the laser for questionable amounts of time, but I'm worried about accidental eye damage while playing. It's not hard to accidentally hit someone's eye while shooting laser guns at each other haha.

Thanks!
 



Immo1282

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I would imagine that most laser tag systems use visible or infra-red laser diodes in their units. Visible lasers under 1mW (Marked out as Class 2/II). Class 2 lasers are considered eye safe unless the user deliberately stares down into the beam (so safe for short-duration exposures needed to register a hit). More powerful visible lasers (Class 3R/IIIa, <5mW) are usable, as they rely on the "eye aversion response" (blinking) to reduce exposure time down. A Class 3R laser will not pose a hazard to someone in the time that it takes to close their eyes as a response to the bright light.

Unfortunately, invisible (including IR) lasers do not fall within this class system as there is no eye aversion response - so if you must use IR lasers, be careful by only using Class 2 power rated ones - i.e. <1mW. This should be enough to detect with an IR photodiode, but you may need to use sensitive detectors to detect hits.

Now if you spread the beam wide enough, the risk is indeed reduced - however a single lens will cause the beam to diverge i.e. it will spread out into a cone which may be poor at range. If instead you're trying to make a "fat-beam" laser, projecting a wide but parallel beam, you'll need an arrangement of lenses called a Beam Expander. This will significantly complicate and increase the expense of this project though.
 

HeroicO

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I would imagine that most laser tag systems use visible or infra-red laser diodes in their units. Visible lasers under 1mW (Marked out as Class 2/II). Class 2 lasers are considered eye safe unless the user deliberately stares down into the beam (so safe for short-duration exposures needed to register a hit). More powerful visible lasers (Class 3R/IIIa, <5mW) are usable, as they rely on the "eye aversion response" (blinking) to reduce exposure time down. A Class 3R laser will not pose a hazard to someone in the time that it takes to close their eyes as a response to the bright light.

Unfortunately, invisible (including IR) lasers do not fall within this class system as there is no eye aversion response - so if you must use IR lasers, be careful by only using Class 2 power rated ones - i.e. <1mW. This should be enough to detect with an IR photodiode, but you may need to use sensitive detectors to detect hits.

Now if you spread the beam wide enough, the risk is indeed reduced - however a single lens will cause the beam to diverge i.e. it will spread out into a cone which may be poor at range. If instead you're trying to make a "fat-beam" laser, projecting a wide but parallel beam, you'll need an arrangement of lenses called a Beam Expander. This will significantly complicate and increase the expense of this project though.
Thanks for the response. I don't necessarily need to use IR, I just thought that was pretty standard for laser tag. I'll be honest, as someone who is new to this stuff, I didn't know you could send signals reliably using visible light. I mean at this point I'm open to using any form of communication, as long as it can reach a decent distance (50m-75m, is that ambitious to ask?). Could a visible/IR <1mW laser be detected at these ranges?
 

Immo1282

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It's very unlikely that you'd be able to get a wide spread out <1mW laser to be detected under non-ideal conditions at that distance without a pretty sensitive detector. You also need to consider ambient light - if you're not somehow encoding the laser with a signal, but just using it as on/off continuous wave (i.e. not pulsed) you'll be battling ambient IR sources. I would guess that this is why Laser Tag is often played in darkened indoor arenas - eliminating ambient light, you create an environment where eye-safe lasers are not only easier to detect - but also eye-safe visible lasers are used and the beams are visible in a room with smoke machines etc.
 

paul1598419

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If you spread the beam out to a cone, you wouldn't be limited to the lower powers that a collimated beam would require. But, the more spread out you make it the shorter the distance you would expect it to work at. I would stick to visible beams as they are theoretically less dangerous because you can see them. In order to get the selectivity you need you might want to modulate the beam so the detector won't go off unless it is struck with the laser. Green would be the color of the beam I would choose as it is more visible when compared to other colors.

If you tried to use collimated beams at lower power, you will suffer needing extreme accuracy to hit the detector....especially since they will be moving. In that case a fog machine would work to help players to see the beams as they fire their lasers.
 

HeroicO

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If you spread the beam out to a cone, you wouldn't be limited to the lower powers that a collimated beam would require. But, the more spread out you make it the shorter the distance you would expect it to work at. I would stick to visible beams as they are theoretically less dangerous because you can see them. In order to get the selectivity you need you might want to modulate the beam so the detector won't go off unless it is struck with the laser. Green would be the color of the beam I would choose as it is more visible when compared to other colors.

If you tried to use collimated beams at lower power, you will suffer needing extreme accuracy to hit the detector....especially since they will be moving. In that case a fog machine would work to help players to see the beams as they fire their lasers.
What power laser would you recommend then? And if I use visible, is the way to detect them similar to the way I detect IR using a photodiode?
 

Shotgundrums

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Interesting write-up. I’d like to see a laser tag rig with nice visible beams. Laser guns firing beams, I love it!! I loved laser tag as a kid. This is pretty cool.
SGD🍻
 

WizardG

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Nobody will play laser tag with me since I put one of those 90W pulsed diodes from a rangefinder in the gun 8-(
 
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paul1598419

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What power laser would you recommend then? And if I use visible, is the way to detect them similar to the way I detect IR using a photodiode?
That really depends on how diverged your beam is going to be. If it makes a 5 inch spot at the distance you want to use them, you could easily go up to 50 mW, but it wouldn't be eye safe close up. Sure, you could detect it with a photo diode, but you would not use an IR filter like you might using IR.
 

hakzaw1

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I did a search long ago and 'then' the lasers had green or red at ~1mW for AIMING the IR laser at the target.. it is not 'set off' by the aiming laser- they still wear eye protection . The TV ads show quick shots of green and red beams going everywhere & while the green looks bright I have no doubt they are very low power. I wonder if the 'players' sign a waiver of responsibility. They all look to be wearing goggles. Very cheap versions are sold for home use.. I have a very used set someplace- Only tested quickly to see if working the put on a shelf someplace.
 

Immo1282

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Ones i've been to definitely used a low-power red as an aiming laser (i.e. not actually triggering a hit) - but the arenas were fairly dark, with fog to highlight the beams. Might be worth getting a couple of airsoft guns instead if you're wanting to play it outside and actually see the visible dots/beams. Alternatively a house with all the lights turned off and a couple of fog machines to mist up the air :)
 

hakzaw1

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OP---''
Hi everyone I'm new here. I did a quick search and didn't see anything on laser tag, but if I missed something or am in the wrong place please let me know :)''

''and...I do not plan to finish my profile w/ my location NOR do I want to fool around with some dumb intro in the welcome section--that shows respect to the forum.. Just help me and do it NOW!! I have school in the morning...

All I have time for is quick searches so you guys can do that for me... ''

Okay that is what we are here for...... NOT.
 




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