Is Time Really A Factor?

[BrittanyGulden]

IR lasers are more dangerous than visible lasers because you can cause damage without realizing it. It is very true that the more you disperse the beam the less dangerous it is. Different people have different ideas as to what power it actually becomes dangerous.

When you are working with 5mw or less the only danger is if you somehow stare into the laser for an extended period of time. With visible lasers this is nearly impossible to do, but with IR lasers it wouldn't be hard. Especially if you leave your laser on by accident. I highly suggest you use some mechanism that makes it impossible to accidentally leave your laser on.

I understand,

My "IR Laser illuminator" would be mounted on my rifle so I am sure you can Imagine I would never look at it anyways (I would never look down the barrel of my rifle or any Gun).

I am sure I can create some sort of Lock Mechanism. I have no kids & this device will only be used on private property W/ no one around except me. I have never had any issues W/ tresspassers but I guess there's always a chance. A very little one in fact because wouldn't "they" have to be starring into my Laser? W/ an area of 7000 acres + I don't see that very likely, especially it being invinsible.

 

[Ibuprofen200mg]

"Area of a Circle = Pie * (R)^2", check your math, multiplying by pie can be tricky and often messy.
Pie = http://edhird.files.wordpress.com/2011/05/apple_pie.jpg
Pi = π
:beer:

 

[Blutquell]

"Area of a Circle = Pie * (R)^2", check your math, multiplying by pie can be tricky and often messy.
Pie = http://edhird.files.wordpress.com/2011/05/apple_pie.jpg
Pi = π
:beer:

lol'd

 

[Ablaze]

Brightness of the sun at sea level: 1020W/square meter
diameter of eye: 25mm2
1,000,000mm2 per m2

Therefor:

The power of sunlight at sea level to burn your eye is the equivalent of a 25.5mw laser.


There are several types of light burn that can be induced by any bright light source. Spots in your eye disappear within half an hour. An shallow burn can take weeks to disappear, and can leave subtle scars that become noticeable if there gets to be too many of them for the brain to form a clear image.

A deep burn will never go away. When most people talk about being burned by lasers less than 50mw they talk about shallow burns.

Also, your original "asshole engineer" was indeed wrong. All materials dissipate heat over time at some rate. The rate of heat dissipation of the back of the eye is hard to define, but it is probably almost as quick as the rate of heat dissipation of water, and water conducts heat quite quickly.

I think you're right: Mounting it on a gun does make it better, since you would only point your gun at something you wish to potentially cause harm to anyway. If you kill a fox, what does it matter if it has spots in it's vision?

 

[Sigurthr]

I had been wondering what the solar irradiance constant was, thanks!

1.02mW/mm2 = solar irradiance at sea level on a cloudless day with the sun directly overhead.

Interesting... a 1W laser with a 4mmx2mm beam (typ.) = 1W/8mm2 = 125mW/mm2 ... no wonder it blows holes in your retinas instantly, that's 122.5X the irradiance of the sun when focused to infinity!

That would also mean that a 1mW DPSS greenie with a beam profile of 1mm2 is the same irradiance as the sun...

 

[Ablaze]

Hmm.. your math is correct, but I think there is a flaw in the logic behind it: Your eyes focus incoming rays of light into points. Therefor, when your eyes are focused to infinity it causes every bit of that 25mm2 "beam" of sunlight to be focused into a single spot on the back of your eye. That's why the sun can burn the back of your eye with the same power as a 25.5mw laser.

a 1 watt laser can also be focused to a single spot, however, I'm pretty sure a 1W laser is "only" 45 times as bright as the sun. (1000 / 25).

Or to put it more technically, 45x more capacity to cause damage to the eye.

Your math would work for how hot a 1w laser should feel on the skin when compared to a ray of sunlight: 125x is pretty darn hot.

 

[BrittanyGulden]

My goal in illuminating 100sq yards was just to give an idea. I would really like to reach out 1000+ if not several, but again this all depends on the Optical Zoom of my designated Camera. Of course my "targets" are relatively small, so I am aiming for a "width" of a few hundred yards.

LED Array & Aspheric Lenses: This device will be mounted atop the barrel of a rifle. My "LED Array" consists of 30+ LED's. I think it'd be a bit impractical to try mounting 30+ LED's W/ Aspheric Lenses atop the barrel of my rifle. -I am trying to keep this device as compact as possible.

2 Or More Single Diodes: Hm, this is going to be a toss up between 1 "expensive" IR Laser VS Multiple "cheaper" IR Lasers. EX: (2) IR Laser Diodes @ 250mW for $50 OR (1) IR Laser Diode @ 500mW for $50. -I know I just threw out random #'s, but it'll give an idea.

Power Level Overlap: I do not understand the whole "hot spots." Let me elaborate: As noted earlier, "diodes" like a 445nm do NOT put out a perfect circular dot. Let's assume that 445nm Laser Diode has a Power Rating of 100mW. When that "beam" is shinned, it is going to put out somewhat of a circle. Now let's assume that "circle" has 100mW going across it. However, there are "Hot Spots" within that circle. Of course, the "Hot Spots" will be "hotter" than the rest of the circle.

So how exactly are Laser Diodes Rated? Do they take the highest Power which in most cases would be the "hot spots" or just the average power? I assume the highest power or "hot spots" for safety reasons. Safety reasons being figuring the OD Rating on safety glasses. -Also have not found much info on this.

Now I know "Hot Spots" are not the same as "Power Level Overlap" & I am not exactly sure how I would calculate that. -It just seems like there are too many variables that come into play, some of which I do not even know exist. Temperature? Humidity seems like it may play a part. Time Factor? ...and so on & so forth


Does anyone know what an average IR handheld laser will "focus" to? -I assume Infinite which is basically what I need in my case because my "targets" won't always be at the same distance.

You guys pretty damn smart lol. -I am just starting W/ my generals & I have brought these questions up to a few of my professors & lost them.... The only one who could comprehend anything was my high school chemistry teacher

 

[Cyparagon]

Brightness of the sun at sea level: 1020W/square meter
diameter of eye: 25mm2
1,000,000mm2 per m2

Therefor:

The power of sunlight at sea level to burn your eye is the equivalent of a 25.5mw laser.

You must mean area, but that means a pupil diameter of 6mm, which isn't realistic for being outside. Try it again with 3mm diameter. Area of 7mm² means a power of 7mW. However, if you've ever tried to burn things in the sun with a magnifying glass, you'll recall the dot isn't nearly as small as the focal point of a laser. This is because the sun isn't quite a point-source. Some of the sun's spectrum isn't transmitted by the cornea, which lowers your exposure even further. 7mW from the sun is safer than 7mW from a laser.

 

[ElektroFreak]

2 Or More Single Diodes: Hm, this is going to be a toss up between 1 "expensive" IR Laser VS Multiple "cheaper" IR Lasers. EX: (2) IR Laser Diodes @ 250mW for $50 OR (1) IR Laser Diode @ 500mW for $50. -I know I just threw out random #'s, but it'll give an idea.

You won't find 150mW or higher singlemode IR diodes because at those power levels your only option is to use a multimode diode. There are no singlemode IR diodes at those power levels, hence my suggestion to use multiple singlemode diodes. You don't want multimode diodes for your application because of the uneven power distribution. Hot spots are dangerous. Using multiple single-mode diodes gives you more even power distribution. I know that you say you'll "only be illuminating your target" but even so it would be unwise for anyone to recommend a dangerous course of action.

 

[Sigurthr]

2 Or More Single Diodes: Hm, this is going to be a toss up between 1 "expensive" IR Laser VS Multiple "cheaper" IR Lasers. EX: (2) IR Laser Diodes @ 250mW for $50 OR (1) IR Laser Diode @ 500mW for $50. -I know I just threw out random #'s, but it'll give an idea.

They meant Single MODE diodes. Because once you go to higher power levels single mode diodes are not available and you get multimode diodes which do not put out a round beam at all. Multimode beams are rectangular, thin and long, and the energy is unevenly distributed across the beam. With out corrective (expensive) optics the divergence is very very bad. Single mode beams are like the beams from low power reds and greens, a nice round spot with a (mostly) even power distribution.

Power Level Overlap: I do not understand the whole "hot spots." Let me elaborate: As noted earlier, "diodes" like a 445nm do NOT put out a perfect circular dot. Let's assume that 445nm Laser Diode has a Power Rating of 100mW. When that "beam" is shinned, it is going to put out somewhat of a circle. Now let's assume that "circle" has 100mW going across it. However, there are "Hot Spots" within that circle. Of course, the "Hot Spots" will be "hotter" than the rest of the circle.

So how exactly are Laser Diodes Rated? Do they take the highest Power which in most cases would be the "hot spots" or just the average power? I assume the highest power or "hot spots" for safety reasons. Safety reasons being figuring the OD Rating on safety glasses. -Also have not found much info on this.

Now I know "Hot Spots" are not the same as "Power Level Overlap" & I am not exactly sure how I would calculate that. -It just seems like there are too many variables that come into play, some of which I do not even know exist. Temperature? Humidity seems like it may play a part. Time Factor? ...and so on & so forth

Diodes (or any lasers) are not rated for power density (hot/cold spots, or how much energy over a certain area) but instead are rated for total output power. Total output power means you take all of the light emitted and focus it on to your measurement sensor. The difference between the hot spot and the cold spot is unknown, and the irradiance (energy per unit of area) is also unknown (but able to be calculated).

Does anyone know what an average IR handheld laser will "focus" to? -I assume Infinite which is basically what I need in my case because my "targets" won't always be at the same distance.

Single mode diodes will focus to infinity rather well, just like any other quality laser beam. It's all in the optics as far as range beyond that of human unaided sight.

You guys pretty damn smart lol. -I am just starting W/ my generals & I have brought these questions up to a few of my professors & lost them.... The only one who could comprehend anything was my high school chemistry teacher

Heh, thanks. We try to spend our free time learning, and try our best to not give answers we don't know. So, when we encounter a question we don't know, we go researching. TONS of info can be found if you try hard enough to find it, part of that is knowing where to look though and that takes experience/insight. The pay off for our hours of research and learning is we get to play with awesome lasers as much as we want!

 

[Trevor]

I'm pretty sure a 1W laser is "only" 45 times as bright as the sun. (1000 / 25).

Of all the things you could be spreading misinformation about, safety is the absolute worst.

Don't let YOUR inexperience hurt someone else.

Trevor

 

[Ablaze]

You must mean area, but that means a pupil diameter of 6mm, which isn't realistic for being outside. Try it again with 3mm diameter. Area of 7mm² means a power of 7mW. However, if you've ever tried to burn things in the sun with a magnifying glass, you'll recall the dot isn't nearly as small as the focal point of a laser. This is because the sun isn't quite a point-source. Some of the sun's spectrum isn't transmitted by the cornea, which lowers your exposure even further. 7mW from the sun is safer than 7mW from a laser.

Actually, we are talking about the maximum potential for eye damage that could be caused by the sun. In every-day life there are times in which a person will walk from a dark area into bright sunlight. In that situation 6mm diameter is conservative. Some people's pupils can be 8mm in diameter. At 8mm diameter the area would be over 50 square mm.

None of this is saying that a 25mw laser would be safe, it's just a little perspective. Our eyes have evolved with the possibility of encountering bursts of light of an equivalent strength to a 25mw laser. That is not saying that 25mw won't cause damage.. we also evolved with the possibility of 6 foot falls, but lots of people still break their arms from falling 6 feet.

An IR laser at night would have significantly more capacity to damage the eye than a visible laser, since it would not trigger a blink reflex or pupal contraction.

Anyway, the true danger from lasers is not the raw capacity for them to burn. The true danger is how many things can appear safe but can in fact be causing permanent damage. Most laser burns will heal 95%, but that 5% that does not heal will really impair your vision if you use lasers carelessly over a period of time. If a novice user gets burned by a laser and then notices the spots in their vision go away after a few weeks they may conclude that they never really needed protection in the first place, and then act in such a way that exposes them to several other laser burns over the next few months. They can then end up nearly blind, all the while thinking they were being safe enough.

Your eyes can only take.. maybe 10 or 20 blasts of light from any bright source in your life before you start noticing impaired vision. That could be from sunlight, or lasers, or maybe even headlights. Using lasers carelessly will use up that quota in no time.

 

[Cyparagon]

Actually, we are talking about the maximum potential for eye damage that could be caused by the sun. In every-day life there are times in which a person will walk from a dark area into bright sunlight. In that situation 6mm diameter is conservative. Some people's pupils can be 8mm in diameter.

Pupils constrict in less than a second. So your proposed scenario is to keep someone in a light proof box outside for 10 minutes to give the pupils a chance to dilate fully, have them stare at a point on a shutter which will open suddenly to reveal the sun behind it? Seems a little unrealistic to me.

Our eyes have evolved with the possibility of encountering bursts of light of an equivalent strength to a 25mw laser.

I've already explained that even if you got 25mW of sunlight in your eye, it isn't the same as a laser because it cannot be focused to a spot as small. At the end of the day, power density is the main deciding factor.

Most laser burns will heal 95%

Sounds like you're just making things up now.

Your eyes can only take.. maybe 10 or 20 blasts of light from any bright source in your life before you start noticing impaired vision. That could be from sunlight, or lasers, or maybe even headlights.

Okay, now I'm SURE you're making things up. Especially considering you just said:

Our eyes have evolved with the possibility of encountering bursts of light of an equivalent strength to a 25mw laser.

 

[Ablaze]

You're being obtuse. 1/2 degree of arc is well within the margin for error, especially considering that I rounded down for all my calculations for intensity of the sun.

All it takes is for you to step out of your cave on a sunny day, cyper. Less than one second is long enough to burn.

 

[Cyparagon]

Less than one second is long enough to burn.

As soon as you even looked outside (let alone stepped outside), your pupils would constrict. It is simply too ridiculous to consider a scenario where you go from complete darkness to staring into the sun in that time span.

You can argue "worst case scenario" all you want, but "worst" is generally taken to mean "worst under normal circumstances." I wouldn't factor in the possibility of a neighbor throwing a massive lens over your head the moment you glance upwards or that an army of furbies is also aiming mirrors at your face - it's just ridiculous.

All it takes is for you to step out of your cave

NEVER gonna happen :shhh:

 

[justinjja]

As soon as you even looked outside (let alone stepped outside), your pupils would constrict. It is simply too ridiculous to consider a scenario where you go from complete darkness to staring into the sun in that time span.

You can argue "worst case scenario" all you want, but "worst" is generally taken to mean "worst under normal circumstances." I wouldn't factor in the possibility of a neighbor throwing a massive lens over your head the moment you glance upwards or that an army of furbies is also aiming mirrors at your face - it's just ridiculous.



NEVER gonna happen :shhh:

How about this, you watch a movie in a dark movie theatre.
then the even darker credits come on,
and then you walk out the exit directly out side and the sun is in your face

doesnt sound that rediculous to me...