# IR - Danger is exaggerated?



## DenisD (May 14, 2007)

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 (May 14, 2007)

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 (May 14, 2007)

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 (May 14, 2007)

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 (May 14, 2007)

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 (May 14, 2007)

*


----------



## Daedal (May 14, 2007)

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 (May 14, 2007)

Daedal said:


> 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 (May 14, 2007)

> 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. 



VaThInK said:


> 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 (May 14, 2007)

2xTrinity said:


> 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 (May 14, 2007)

2xTrinity said:


> ...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 (May 14, 2007)

VaThInK said:


> 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 (May 14, 2007)

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 (May 14, 2007)

@ 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 (May 14, 2007)

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 15, 2007)

VaThInK said:


> 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 (May 15, 2007)

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 (May 15, 2007)

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 (May 15, 2007)

Ashton said:


> @ 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 (May 15, 2007)

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


----------



## Daedal (May 15, 2007)

flashlightpoor said:


> 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.
> ...



That is a very kind offer from your side, and thank you for that. The reason why IR is considered a false adverising tool is because collimated or not, leaked IR goes into the overall rating of the pointer. Say you bought a 30mW but it turns out it's a poorly filtered laser putting out only 3mW of green and 27mW of IR. The seller will tell you "it IS 30mW comming ot of that lense!" Hence the arguement.

Hope that helps;
DDL


----------



## flashlightpoor (May 15, 2007)

Daedal said:


> That is a very kind offer from your side, and thank you for that. The reason why IR is considered a false adverising tool is because collimated or not, leaked IR goes into the overall rating of the pointer. Say you bought a 30mW but it turns out it's a poorly filtered laser putting out only 3mW of green and 27mW of IR. The seller will tell you "it IS 30mW comming ot of that lense!" Hence the arguement.
> 
> Hope that helps;
> DDL



I am familiar with the argument. I just don't know how common it is-- and without proper test equipment I am not sure how everyone else knows. i bought a 30mW green laser from dx. I measured it and found 32-35mW of green light and zero IR. I think it would be helpful to the forum if people who bought the 50, 100, 150, 200 mW lasers could defnitively say what their laser is emitting. Hell, I am curious myself. I have micro joule to mega joule power meters and spectrometers I just thought if I could shed some light on this issue it would be helpful.


----------



## Daedal (May 15, 2007)

flashlightpoor said:


> I am familiar with the argument. I just don't know how common it is-- and without proper test equipment I am not sure how everyone else knows. i bought a 30mW green laser from dx. I measured it and found 32-35mW of green light and zero IR. I think it would be helpful to the forum if people who bought the 50, 100, 150, 200 mW lasers could defnitively say what their laser is emitting. Hell, I am curious myself. I have micro joule to mega joule power meters and spectrometers I just thought if I could shed some light on this issue it would be helpful.



The 30mW DX lasers have 0 IR. They are filtered. Their lasers are filtered all the way to 50mW. Past that there is no IR filtering. They are actually kind enough to state that on their website. 

It's good to know that you have all that test equipment handy. Makes me want to go test my pointers at the university here. They got a huge optics gollege, and they have a very nice set of lasers from what I hear. Cutting/slicing/dicing/burning/blinding in all colors and power levels! Too bad they have a magnetic key access on the doors. I shall make my way in there soon though. It will be fascinating! :devil: Hopefully I'll provide photos too 

Thanx;
DDL


----------



## Ashton (May 15, 2007)

Psudo and... I think senkat, but not sure... both posted graphs showing the readings on the lasers AFTER passing a industrial-grade IR filter. IIRC, the 100mw is really ~75mw green and teh 200 is ~170my green or so.

@ flashlightpoor: you dont have to be a university anymore to purchase a lasercheck, I believe there are no less than 5, possibly more, members on ehre that own such a device, and a similar or even larger number over at LC, and almost every single greenie on ebay uses the green+IR marketing strategy, and many other legit companies as well!


----------



## allthatwhichis (May 15, 2007)

Daedal said:


> The 30mW DX lasers have 0 IR. They are filtered. Their lasers are filtered all the way to 50mW. Past that there is no IR filtering. They are actually kind enough to state that on their website.


 
I think this bothers me more than anything... Why would you take the IR filter off the higher power lasers? :huh2: That's completly stupid, AND to advertise it... :scowl: I would think you would want to filter the higher power lasers... Actually, ALL DPSS LASERS SHOULD HAVE IR FILTERING!!! but hey, there is that perfect world I have been dreaming of... :lolsign: 

Has anyone taken a higher power DX and measured it with an IR filter? Maybe done a side by side with a 50mW DX? I want to assume they are probably the same laser...


----------



## VaThInK (May 15, 2007)

Daedal said:


> 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.
> 
> ...



If you put it this way. There's no need to point out that IR is dangerous. You should state that *all* lasers are dangerous, *period*, which is somewhat not the OP is all about. Besides, I guess we're all grown up here and no one under 18 years of age should be allowed to "play" with one. If they decided to have a go at it, it's their decision and responsibility. By the time the power of IR laser becoming a threat to our body, the visible beam is already way more dangerous than that. Unless your talking about a dud laser that puts out 190mW IR while only producing 10mW visible beam or a totally IR laser. Then you are right. A lot of care should be taken.

The way you think about IR beam is just like saying "Be careful, this dynamite fuse is hot when ignited", while you should be worrying much more about the aftermath when it explodes. Bottom line, no one should toy around with dynamites. If someone wish to do so, it's the individual decision and be responsible about it. Same thing goes with all lasers. It's not a toy and IR is not more dangerous than visible beam except when only IR beam is being produced or in a dud laser situation as I mentioned before. Because our eyes is not very sensitive to IR as you said. I hope you understand what I'm trying to say. No offense intended.

Peace.


----------



## SenKat (May 15, 2007)

I REALLY have to chime in here - (Mike - you KNEW I would, didn't you ?)

I had a Coherent 1 WATT 808nm fibre coupled diode - I did many experiments with it, and one that surpassed the rest was measuring it's out put at varying distances. at less than an inch, it burned things very well - so well, in fact I was very concerned I would suffer flash blindness by the match igniting ! I measured the output with the Coherent lasercheck, and that device registers ALL the energy - not really at specific wavelengths too well. I set it on 808nm, and did measurements based on distances - at less than an inch, it was putting out 1.2Watts of energy. Incresing the distance, I continued the measurements - now it is important to point out that just because it is fibre coupled does NOT mean it is well collimated - because it certainy is not ! At just over a foot, I ceased to obtain ANY readings from the power meter - why, you ask ? It is because at certain distances, the IR foods out, and you will not receive any negligble readings. Now, this was all measured with a non-collimated IR beam - not a pointer ! So, I decided to test a few other things along the way, and a touted 120mw pointer (greenie) was putting out only 110mw of green light AFTER an IR filter (again, less than an inch measured) but 360mw BEFORE an IR filter ! OMG !!!! I was petrified ! Imagine that much power from an el cheapo Fleabayser !!! WOW ! So - I increased the distance - guess what ? After about a foot, the readings dropped to 110mw PERIOD. So - this lead me to believe - and everyone who has NOT done any kind of readings to support their claims, are just spreading rumors IMO - without cold, hard, facts, you are just talking from what you have heard - I was lead to believe that IR was pretty much useless after about a foot ! Okay - that is NOT a precise measurement - but I have measured the output of MANY lasers - red, green, IR, mixed, and received the same results every stinking time I have done the measurements ! 

I have yet to have heard of anyone receiveing a laser from DX that was not filtered - the thing is - what is the quality of the filter ? They state that NONE of their lasers have IR filters on their website - so it must be true, right ? NO ! They put that there, in case some idiot shines the laser in their eyes and suffers damage, so they do not get sued ! All of the DX lasers 50mw and below have HIGH QUALITY filters. Period. They all do. I am basing this on my measurements of close to 15 50mw ones, and everyone elses (so I guess it is rumor) measurements of their 20 or 30 mw DX lasers. Psuedo tested a 100mw DX laser, and it came out that is was horribly filtered - there WAS a filter in it - it was just not too darned good at its' job ! So, in summary - if you are working with ANY laser close up - wear eye protection. The amount of IR that is going to reflect is going to be neglible after about a foot - unless you have a pure IR source - focused down perfectly (The Laserglow Hades series springs to mind here) and you do experiments that could cause reflections. Without that pure, focused, collimated laser source, you are NOT going to get any kind of dangerous amounts of IR reflected back at you, period. Now - because EVERY laser is different - you should still wear goggles if you are working with power levels in excess of 5mw - you SHOULD - so if your eyes turn into smoking cinders because you were reckless - don't come tapping your cane on my doorstep, looking for pity - just don't. The thing is - be SAFE - take care of your eyes - and respect laser sources for the amazing scientific, and fun item that they are - be responsible, and you will be able to read this post many many times over - and laugh at it, point fingers, giggle, whatever -but the dangers of IR light from uncollimated sources is neglible in my experience - where my experience is not complete by any stretch of the imagination - it also is rather vast, and I have done the tests, and measurements to support my claims. Whew. Okay, done. Now, this erply is NOT pointed at anyone - so if you are offended, it is because of my typing skills, lack of spell checker, or my personality - but you cannot argur with cold, hard facts as they have been presented. Thanks for reading - off to work now !


----------



## VaThInK (May 15, 2007)

Wow, thanks SenKat for sharing your experience. Very interesting observation. I don't have any proper equipment to get exact measurements like you. All of my statements are all based on my personal experiment results in the past. Good to know that your finding is backing up my results. :thumbsup: However, I didn't know that IR radiation is actually fanning out that fast. Now I do.

I wasn't surprised though when you said without IR filter your Fleabayser is producing 360mW of green and IR as some of the IR from the pump diode that is lost during the conversion has to go somewhere. The conversion efficiency from IR to green that I've heard is at 20% maximum these days. So the other 80% is either absorbed by the crystal or escaping outside along with the green.

PS: You've made me jealous SenKat. I want a meter too. :mecry:


----------



## SenKat (May 15, 2007)

VaThink - get one from Tony and Holo !!! Check out the sales area, there is a thread there called LPM-1 ....it is an excellent meter, and has better features than my laser meter from Coherent. A GREAT choice is what it is !


----------



## VaThInK (May 15, 2007)

Argh, comes to $240 with the attenuator not including postage. Still a bit expensive for me. Why does laser meter has to be so expensive (I know LPM-1 is cheaper compared to Coherent LaserCheck, but still). Sigh. By the way, has the price comes down yet by any chance? Might ask Tony and Holo about this. Thanks SenKat for letting me know. =)

EDIT: Nop, the price is still $199 for the standard unit. Anyone interested in starting a group buy?  Count me in. :naughty:


----------

