IR - Danger is exaggerated?

[DenisD]

1 IR is not well collimated.
2 if it's a diffuse reflection, the power decreases proportional to square of distance.


IF it's safe to look on 3W led flashlight spot from the 3 feet, why it's unsafe to look on 0.2W IR spot?

I think the only danger is to look on near reflections, and stare IN to the switched on laser pointer that has broken KTP crystal.

Am i right?

 

[David_Web]

The point is that you can not see IR and thus you don't know how intense it is or the size of it. You also don't feel it when it hits the eye so you could burn a hole in the eye before you realised it. You also don't have any reflexes to prevent it from happening.

And just because it's diffuse doesn't mean it follows that behaviour. In fact nearly no surface in existence does this. Besides it's the mW per m2 that counts so it does not matter how long away you are from the surface unless particles or other things block or scatter the photons.

And collimated or not, it will be in your eye.

 

[VaThInK]

Based on my personal experience it is a little over exaggerated. However it is better safe than sorry.

David_Web: I agree with you but not entirely. Your last comment seem to contradict with the one before. You're right it's the power per area that counts. Collimated beam is the one that does real damage, unless we're talking about 100W+ beam. The latter got enough power to burn even when not collimated. In the end it's all about power per area. Correct me if I'm wrong.

Cheers.

 

[Daedal]

A 5mW greenie would need a 200mW IR diode, typically. If you think it's ok to point 5mW into someone's eye for the sake of a very dangerous joke and end up pointing a 200mW by mistake because you don't know of or see the IR, then the risk is greatly underrated in my opinion. The typical consumer and user of these lasers is completely oblivious to IR, and if they can't see it, they don't know how bad it is. IR is very dangerous, maybe not to you, but to many others it poses a huge threat. Consider the teacher that uses a high-power greenie in class thinking it is ok to point with a green laser, when in fact the projections screen is glowing bright with IR! Now this oblivious teacher is not knowingly hurting the students, and the students wouldn't know it either.

Also, on a side note, if you have a flashlight that puts out the equivalent of a 200mW light and you shine it at 3ft away in a dark room, you will need to close you eye lids a bit until your eyes adjust. With IR, on the other hand, you have 200mW of unfiltered light passing through a completely open iris, that in itself is harmful!

Pointing a laser from a very upclose distance at the concave part of the spoon will reflect green light while expanding it, while essentially collimating the IR.

There are many situations where IR can pose an unforeseen or imaginable threat. IR is not over exaggerated or overrated.

Hope everyone stays safe;
DDL

 

[VaThInK]

Hum, I must disagree. When we're talking about well collimated IR beam like in a laser pointer or module then yes you're right, it is very dangerous. Heck any beam that is well collimated is harmful. Especially when the beam diameter is very small (eg: 1mm).

However, to put things into perspective. Did you know that a light bulb (filament type) based heater puts out IR as well? Imagine a 300W bulb generating lots of heat. Do you think that it's dangerous? I don't think it is. Unless you can think of a way to collimate the beam into a tiny spot, then it will burn metal like crazy. Let alone your eyes. Otherwise, just like the OP said, it's just like looking at a 3W LED flashlight from a distance, which is quite safe.

Another example is that if I remember correctly, we get about 1000W/m2 (I may be way off, can't remember exactly) of light on the surface of the earth. Is it dangerous? Does it burn things? Not really. Get a magnifying glass and focus it to a tiny spot on a black paper and hey, fire.

Well, in the end, this is what I think. Any light source that are not collimated is less dangerous than the collimated one. It depends on the optical power output as well of course. Hence, power per area that's matter.

EDIT: In regards to the sun light optical power, I have found a reference to it. It's at http://en.wikipedia.org/wiki/Sun under Overview section.

EDIT2: I suggest everyone to have a read at it if you haven't already. Pretty good information I reckon. Especially if you want to know more in this area. They also state that "Looking directly at the Sun causes phosphene visual artifacts and temporary partial blindness. It also delivers about 4 milliwatts of sunlight to the retina, slightly heating it and potentially (though not normally) damaging it.". Out of 1000W/m2 you're only getting about 4mW if it's not collimated. Interesting.

 

[macforsale]

*

 

[Daedal]

It is sometimes better to be safe than to be sorry, and that may be just me. I personally value my vision greatly and would never induce blindness to myself or anyone around me, if it's something you can afford to give up, more power to you.

--DDL

 

[VaThInK]

It is sometimes better to be safe than to be sorry, and that may be just me. I personally value my vision greatly and would never induce blindness to myself or anyone around me, if it's something you can afford to give up, more power to you.

--DDL

As I said before, you're right. I'm not disagreeing with you totally. I'm just trying to share what I think to the OP that IR sometimes is a little exaggerated. He stated that " IF it's safe to look on 3W led flashlight spot from the 3 feet, why it's unsafe to look on 0.2W IR spot?". If the 3W LED flashlight is well collimated, the situation would be different. Indeed safety always comes first.

macforsale: I think both counts. Coherent and collimated.

A little off topic. I'm not sure how do they produce coherent beam from a flash tube pumped YAG laser. Is it the crystal that's doing the job? Anyone knows?

 

[2xTrinity]

I thought that with lasers it is the coherent (in-step wave front) that adds to the danger and not so much the collimated aspect.

I'm not sure how that affects things. If the eye-damage is cauesd by heating of the retina, the wavefront shoudln't make a difference. If it's caused by the photons themselves interacting with the cells (I'd worry about those Near-UV "blu ray" lasers), it might.

One thing about lasers though is that their light is emitted from a very small point -- much smaller than the die surface of a 3W IR LED, or even a 500W heat lamp filament. Even though all of those are emitting IR light in a non-collimated manner, I'd expect the laser light to be the most dangerous as it has the highest surface-brightness, that is, your eye will focus it to the smallest point on the retina. It's somewhat like the difference between looking at a bare filament bulb, and a frosted incandescent bulb, where both are producing the same amount of power. I believe that is the true danger of the lasers -- the fact that even at low intensity (power/area), the light is concentrated onto a very, very small spot.

macforsale: I think both counts. Coherent and collimated.

A little off topic. I'm not sure how do they produce coherent beam from a flash tube pumped YAG laser. Is it the crystal that's doing the job? Anyone knows?

The YAG crystal itself is where the lasing happens. The flashtube simply excites the molecules in the crystal, which remain excited until they are hit with a photon, and spontaneously emit a coherent "copy" of that photon. This leads to a chain reaction and a pulse of coherent light.

In the case of a green laser, the YAG is being continuously pumped to produce coherent IR.

In general I would say IR isn't much of a worry, especially for what I use green lasers for -- pointing at stars outside (not many close by mirror-like surfaces to worry about). However, one thing I have seen that has looked pretty dicey is a physics professor shining a green laser pointer (~5mW) through a diffraction grating toward the ceiling, from waist high. He could easily have been hitting himself with diffracted IR beings from fairly close range.

 

[VaThInK]

I'm not sure how that affects things. If the eye-damage is cauesd by heating of the retina, the wavefront shoudln't make a difference. If it's caused by the photons themselves interacting with the cells (I'd worry about those Near-UV "blu ray" lasers), it might.

May I ask why near-UV in particular? I thought the dangerous one is IR and above as the wave gets longer. Hint: CO2 laser at 10.6um can be categorised as microwave as well and see any material as opqaue even clear glass.

 

[VaThInK]

...the fact that even at low intensity (power/area), the light is concentrated onto a very, very small spot.

If I understand your post correctly, yes this is partly what I'm trying to say. If IR light is not well collimated, it's just an ordinary flashlight with the exception of being invisible to human eye, which is harmless.

To make things clearer, as I mentioned before, on the surface of the earth we get about 1000W/m2 but only get around 4mW on our retina. So if a laser is producing 100mW of light at about 1mm diameter, the W/m2 would be hell of a lot greater than 1000W/m2. Roughly about 25000W/m2 to be exact! (I hope my maths is not playing up on me ;P). Hence, a lot stronger than the sun light and is highly hazardous. Keep in mind that it is very closely related to W/m2.

Reference: http://en.wikipedia.org/wiki/Sun under "Sun observation and eye damage" section.

Sorry for the double post though.

 

[DenisD]

So if a laser is producing 100mW of light at about 1mm diameter, the W/m2 would be hell of a lot greater than 1000W/m2. Roughly about 25000W/m2 to be exact!

In this case visible laser dot is more dangerous cause it size smaller then the IR.
And IR power part in laser radiation <50% even in bad nonIRfiltered pointers.

Can anybody calculate power from the omnidirectional point light source?
I just want to know, What distance is safe for 30mw laser to look on to the light spot on well diffusion(non glare(wall, brick, wood etc.)) surface?

btw, how powerfull IR illumination led in camcorders?

 

[Tritium]

I have wondered for a while: How much IR are you getting while gazing at a roaring campfire for several hours? Its obviously putting out a LOT O WATTS.

Thurmond

 

[Ashton]

@ vathink:
with UV, the chemical reactions take a backseat to the photogenic reactions. This is called Skin Cancer, while IR and radio cause RF burns, which are not nearly as dangerous. IR is safe and fun compared to UV!

I just wanted to point out that a major reason people complain about the IR in green lasers is because it's used as a falcifying marketing tool. the laser is "100mw" but this is 30mw of green and 70mw of IR! (which is also cheep, a 1W IR diode is like $20, $10 or less in bulk! while ture green laserlight is curently very expensive per mw (though this will change when green diodes are avalible))

Most of us know the dangers of IR, we're jsut mad about the marketing scam, think of it like going to a burger store and ordering the LARGE fries, only to find out that the box is taller --- but only half as deep, so you're getting as many or LESS than the smaller fries for the same $$$!

Granted IR is not a toy, but keep in mind the bitching is about $$$ mainly, and also IR is still laser energy, and should be treated as such.

 

[Daedal]

Ashton, good point about the UV. Thank you for clearing that out.

As about the IR, I still stand by my statement. Invisible light energy poses a very true and very dangerous threat. We are not blind to IR, but we are very insensitive to it. It is harmful, and it is produced by huge amounts in green laser pointers, and they should not be treated as a toy by anyone. At least until green LD's are available, as Ashton pointed out.

GL;
DDL

 

[2xTrinity]

May I ask why near-UV in particular? I thought the dangerous one is IR and above as the wave gets longer. Hint: CO2 laser at 10.6um can be categorised as microwave as well and see any material as opqaue even clear glass.

The shorter the wavelength, the more dangerous. The reason is because energy in the form of light is transmitted as photons. Let's say there are two light sources of identical properties (power etc) except one is IR, the other UV. Both will be sending the same amount of total energy in a given time, however, the IR will be sent as a whole bunch of low-energy photons, and the UV will be sent as fewer higher-energy photons. In the case of the UV, any one of those photons is energetic enough that a collision with a skin cell, or eye cell, can kill the cell or cause a mutation -- that is why UV light causes sunburn (in the case of killing cells), and cancer (in the event of causing a cell mutation). No matter how much power there is in the IR there is though, no single photon collision will ever be rnough to cause a cell mutation.

The other way that light can cause damage is through heating -- essentially, all the energy from the photons is absorbed. Wavelength is irrelevant when talking about heating up things like black tape, match heads, etc. In the case of heating damage on the retina, green is going to be the worst -- as that is the wavelength that the eye focuses most sharply.

If I understand your post correctly, yes this is partly what I'm trying to say. If IR light is not well collimated, it's just an ordinary flashlight with the exception of being invisible to human eye, which is harmless.

While I don't think the IR from a typical pointer is nearly as dangerous as the actual green light coming from the laser, it is more dangerous than an IR flashlight as the light is coming from a smaller point-source.

Consider which is more irritating to your eyes -- looking at a 50W frosted incandescent lamp, or a 50W CLEAR incandescent lamp. Both have similar spectrum and your eye is absorbing a similar amount of power in both cases, but staring at the clear lamp would be worse for you since all the lgiht is concentrated into a small image of a filament on your retina, instead of a large image of a frosted bulb.

I just wanted to point out that a major reason people complain about the IR in green lasers is because it's used as a falcifying marketing tool. the laser is "100mw" but this is 30mw of green and 70mw of IR! (which is also cheep, a 1W IR diode is like $20, $10 or less in bulk! while ture green laserlight is curently very expensive per mw (though this will change when green diodes are avalible))

Most of us know the dangers of IR, we're jsut mad about the marketing scam, think of it like going to a burger store and ordering the LARGE fries, only to find out that the box is taller --- but only half as deep, so you're getting as many or LESS than the smaller fries for the same $$$!

In most cases, if someone's going to be dishonest about the power ratings, they'll usually just pull a number out of thin air, rather than systematically measuring the IR and using that. However, I've read lots of complaints about for example the 20mW lasers from DX which apparently do emit 20mW of green, plus some amount of IR, due to potential safety concerns.

I have wondered for a while: How much IR are you getting while gazing at a roaring campfire for several hours? Its obviously putting out a LOT O WATTS.

Again, it's not so much the wattage that's relevant, but how concentrated that wattage is on your retina. A fire, or a hot road surface on a summer day for example are diffused light sources. A IR LED, or IR laser are not.

 

[chuck]

Good points...but let me play Devil's advocate for a moment.

It has been said that *any* IR exposure is bad, and that walking through a scanned beam (like entering a tunnel effect) is enough to cause significant damage in the "wink of an eye."

At what power level is this actually true?

Don't get me wrong...I have a healthy respect for IR. But, let's say a 20mw IR beam, scanned across the field of vision at high speed... Would it ACTUALLY cause any measurable damage? Not cumulative damage...not long-term staring directly into 600+mw beams...but something the average user has easy access to on this board.

I tend to believe that the claims of immediate and catastrophic IR damage from something like a common 5-30mw greenie ARE a bit exaggerated.

Perhaps someone could set me straight?

-- Chuck Knight

 

[Ashton]

20mw of laserlight IS enough to cause permanent irreversable eye damage. 15 is enough to cause it. Scanning at high speed does not decrease the risk (atleast not the speed you'd be using) I dont have it handy, but there's a wonderful site where a guy wrote up his experiances with a low-powered laser and permanent eye damage, including visual representations!

 

[flashlightpoor]

@ vathink:


I just wanted to point out that a major reason people complain about the IR in green lasers is because it's used as a falcifying marketing tool. the laser is "100mw" but this is 30mw of green and 70mw of IR! ............

I read this all the time on this forum but has anyone measured this?
I mean measured with a laser power meter and not the distance to pop a balloon or light a match? -- because decreased match lighting distance doesn't mean more or less green or IR light. it might mean your crystal is bad or your optics are misaligned or you pot is bad, etc.

I guess what I am saying is if you don't know how much light of whichever freq, at what power, and if it is or isn't collimated you really don't know what the danger is.


I lwork at UCLA in a laser lab. if anyone wants their lasers measured I would be happy to do it. And if you live in the area you are welcome to come buy (after hours or weekends) and I will help you measure it yourself.
oh yeah and pm me if you want to send me your laser or visit.

 

[Daedal]

Let's consider the consequences here... a 14-year-old kid is surfing the net and stumbles across your post saying that a 30mW greenie is not very harmful to the eye when scanned at high speed, at $30, he goes and buys one. Then, he gets all fired up and excited about the laser and after that goes and buys a 100mW greenie for $100. Still, not a lot of damage, but quite the considerable excitement is getting to this kid. One day, he's playing around with his friends and, as a practical joke, moves the laser very quickly infront of his friend's eyes. You finish the rest..

The right thing to know is IR IS DANGEROUS! If it's just pure green pointing with .2W on a pin point, you would respect that power and not look into it! IF you do, you'll be blind for atleast a minute, and God only knows what kind of permanent damage you'd cause in that small time frame, regardless of how small a time frame. consider now the fact that you cannot see or tell how bright the IR is. Also, I take it as a rule of thumb, a 200mW spot means instant blindness. This is me, and I really want to continue to see well into my 70's. As for those opposing to this statement, I don't know what to tell you.

To each his/her own I guess;
DDL