Safe mW for Tactical Laser?

[shintashi]

hi,

I've been wondering what the safe/recommended mW for a rifle/pistol mounted tactical laser is? I've got an idea for a laser that uses a cross lens adapter like the ones used in cross line levelers, and I'm not sure how low I should take the mW.

I've seen ranges of 5mW to 20mW and I figured the cross would diffuse the beam intensity greatly, but I'm not sure by how much. I understand lasers have to be treated like a firearm in terms of safety, but if they are already attached to the business end of a loaded gun, you've already got safety rules in place and more serious problems than blindness.

With target shooting, it makes sense you don't want your target going up in flames because the shooting range people might kick you out as a fire hazard, but I'm not sure what the burning laser/range/mW variables are, since I've only lit a match at 10 feet and the shortest distance at ranges are between 15 ft and 21 ft.

I was also wondering what's the greatest difference/multiplier I can put in a laser in terms of power, without having to use 2 diodes, before the thing doesn't even turn on? Like can I go from a 20mW to a 200mW, or from a 5mW to a 750mW?

 

[Bluefan]

A safe level would be 1mW/cm^2 for any point where somebody can look into the laser, that includes any reflections. Laser safety is different from gun safety, pointing a gun to the ground is probably safe, but in case of a reflecting ground it's not laser safe. So determine the closest distance from the laser anyone could be when it's on and then pick a laser with a maximum of 1mW/cm^2 at that point and you'll be safe.
1mW/cm^2 is conservative to be safe, people around here consider 5mW total as safe enough so that would stretch the limit to almost 10mW/cm^2.

 

[shintashi]

A safe level would be 1mW/cm^2 for any point where somebody can look into the laser, that includes any reflections. Laser safety is different from gun safety, pointing a gun to the ground is probably safe, but in case of a reflecting ground it's not laser safe. So determine the closest distance from the laser anyone could be when it's on and then pick a laser with a maximum of 1mW/cm^2 at that point and you'll be safe.
1mW/cm^2 is conservative to be safe, people around here consider 5mW total as safe enough so that would stretch the limit to almost 10mW/cm^2.

Any idea how much the cross in this video (time: 2:50-2:57) 1W Spartan 447nm demonstration and Arctic Lens's attached! - YouTube diffuses the light? I'm just going to guess around x1/200-300 based on the frame in 2:57 but I noticed with these alternative lenses, the center of the patterns is more intense than their periphery/edges.

I'm also curious about the low/high power range, because (hypothetically), assuming I went from a 500mW down to say, 200mW by some switch, and then added a cross lens, wouldn't that put my cross at about <1mW/cm^2?

Obviously I'd want some kind of measuring devices and tests, but I'm trying to get some ball park figures in advance so I don't buy the wrong diodes.

 

[Bluefan]

You'd have to measure it to be sure. Your estimate of a 200 or 300 times reduction may be valid if you measure at 2 meter distance, that means that below that distance the laser is dangerous. I'd recommend a smaller safety distance just to be sure. Also, I hope you know where to get lasers that survive being mounted on guns, the recoil is quite violent.

 

[Benm]

It's going to be very difficult to calculate - it all depends on how the cross optics actually fan out the beam: its not to be assumed that all parts of the cross pattern are equally bright, for example.

Most cross generating optics i've seen create a cross that projects at about 90 degree deflection angle... probably completely useless for long range aiming as the cross would not be visible even with a high powered diode.

 

[shintashi]

It's going to be very difficult to calculate - it all depends on how the cross optics actually fan out the beam: its not to be assumed that all parts of the cross pattern are equally bright, for example.

Most cross generating optics i've seen create a cross that projects at about 90 degree deflection angle... probably completely useless for long range aiming as the cross would not be visible even with a high powered diode.

is there a possibility for a 30 degree rather than a 90 degree, like a custom lens or something? Right now we are only shooting at 7 meters, with silhouette targets being rather large, still, if the width is considerably greater than 1 meter at 5+ meters, that's a bit much. At 90 degrees the range is the width.

Who makes custom lenses?

 

[Benm]

I havent seen any with considerably lower width - those cross/line generating optics are really simple things and consist of no more than some plastic ridges that scatter the beam.

There are 'holographic' caps though, often found with lowcost toy lasers that allow you to project things like an arrow or heart shape with only a few degrees width. Perhaps they also make them projecting a cross pattern, though i have to idea where to buy them (try ebay?).