So whats the fuss bout IR??? i mean i though it was absorbed by most materials making reflections unlikely. also wouldn't it only be really harmful if it was focused at the eye, i heard IR does not focus like the visible light or something so i suppose it could get in your eyes if the laser was sort of pointed towards your eye but not directly. im rambling but just wondering under what circumstances can IR get into your eye at levels that can damage it? tho if the IR wasn't concentrated and spread over an area wouldn't it have very little energy??
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FrozenGate by Avery
whats the fuss about IR?
- Thread starter Thories
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SenKat
Guest
The MAIN danger about IR is that most of the time, we are talking about green lasers, right ? well, if the IR is mixed with the beam, and LOTS of folks do not use goggles, even for close up experiments - the IR can bounce off of lots of different materials, so when you are leaning in with an inexpensive ebayser, trying to get that stubborn match to light....you squint, because the green is so bright - your pupils dialate because you squint, and BAM ! IR light infiltrates into your eyebal, causing blind spots. Granted that is an extreme example, and I have dealt with a few IR spewing lasers in my time - no blind spots yet (thankfully !). The best bet is to be cautious....you just never really know what material MAY actually reflect it, so that is the reason why most green blocking goggles have a high VLT (Visible light transmission) - so your pupils do not get overly dialated, and allow the IR in....
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Along the same lines and SenKat said, a lot of people do experiments in dark or dimmed lighting conditions, where your pupils dilate to allow in more light. Since our eyes don't react to IR, IR could be streaming in there and the pupil would stay wide open, allowing it lots of light.
Not everything absorbs IR- if it did, we'd have no need for IR filters in the optical path of the lasers, would we? I saw a great experiment recently, where a £5 webcam was given a filter to eliminate human-visible frequencies (made out of a piece of over-exposed film negative as it happens). Thus you had a cheap IR camera. And quite a few things were discovered to be IR transparent, such as a bottle of cola.
One thing that will absorb IR nicely is your retina.
And don't, unless you get a proper visual field test, assume that you are without "battle damage". You brain is superb at hiding defects in your visual field from you, until it gets very far gone. By and large, we're blind to our own blind spots!
And everything I have said about IR goes for UV too.
Not everything absorbs IR- if it did, we'd have no need for IR filters in the optical path of the lasers, would we? I saw a great experiment recently, where a £5 webcam was given a filter to eliminate human-visible frequencies (made out of a piece of over-exposed film negative as it happens). Thus you had a cheap IR camera. And quite a few things were discovered to be IR transparent, such as a bottle of cola.
One thing that will absorb IR nicely is your retina.
And don't, unless you get a proper visual field test, assume that you are without "battle damage". You brain is superb at hiding defects in your visual field from you, until it gets very far gone. By and large, we're blind to our own blind spots!
And everything I have said about IR goes for UV too.
D
dr_pressure
Guest
From "Laser safety" on wikipedia
Say I am outside at night pointing a green laser (>50mW) into the sky. I have someone next to me and I am pointing to something (hoping there are no mirrors on the moon or random stars.)
That is safe, correct? I just decided to buy a laser this morning after seeing a video on youtube. I think I have got most of the safety issues covered. This is the last one I need to be reassured on.
Thanks
That is safe, correct? I just decided to buy a laser this morning after seeing a video on youtube. I think I have got most of the safety issues covered. This is the last one I need to be reassured on.
Thanks
Gazoo
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Just use common sense 
...Yes you can point the laser at the sky or anything else that will not reflect the beam back to your eyes. Don't point it towards other people, animals, cars, planes and so on.
For example I point my X105 at the wall n my home but it is painted with flat white paint. The dot is extremely bright and I would not stare at it. If my walls were painted with glossy paint, then I would wear goggles.
If you plan to burn anything up close you will need goggles.
...Yes you can point the laser at the sky or anything else that will not reflect the beam back to your eyes. Don't point it towards other people, animals, cars, planes and so on.For example I point my X105 at the wall n my home but it is painted with flat white paint. The dot is extremely bright and I would not stare at it. If my walls were painted with glossy paint, then I would wear goggles.
If you plan to burn anything up close you will need goggles.
Shiftline: a scanned beam will always be safer than a stationary beam, as it is in many places at once, so will not impart the same energy as a fixed beam. However that is not safe to say that any scanned beam will be a safe beam, as that will depend on initial beam power and how fast it can be scanned.
But custom built low powered scanners like yours, will be safe to view in a medium sized room as long as the mirrors keep moving and the scanner keeps scanning.
Jase
But custom built low powered scanners like yours, will be safe to view in a medium sized room as long as the mirrors keep moving and the scanner keeps scanning.
Jase
As far as diffuse reflections/sources are concerned I doubt the danger level given to NIR/IR. Some of it just doesn't add up.
***It should be noted that given the same intensity and exposure all light with the exception of UV is equally as dangerous no matter the wavelength. Exposure is reduced for visible wavelengths compared to invisible ones because of pupillary responce. ALL DIRECT (OR SPECULAR) OCCULAR BEAM EXPOSURE IS HIGHLY HAZARDOUS ABOVE 5mW/cm*2***
Eye Damage:
Eye damage happens in two ways: Intraoccular Heat-Related Tissue Destruction (burning the inside of your eyes) and Receptor Cell Overstimulation (flash blinds).
IR:
As true IR is invisible it can not cause Receptor Cell Overstimulation, so the only damage it could cause would be heat damage. Normal irradiance calculations would apply. The ONLY reason IR would be more dangerous than NIR is because there would be no pupillary response so there is greater risk in accidental direct exposure.
NIR:
I am curious to find out if it is really as dangerous as hype suggests it to be, NIR is emitted in large quantities by many many everyday items. In the case of pointer lasers it is often 808nm, which is rather visible. I have been VERY cautious with my new 150-200mW 808nm burner as I'd say it looks as bright as 1mW 670nm. I realize that specular reflections and direct beam exposure is a tremendous hazard, but what about diffuse reflections from >2ft. The beam has a HUGE divergence (something like 75mRad), so diffuse reflections of a spot 10cm+ in diameter shouldn't be harmful, right? 10cm*2 of 150mW = 15mw/cm*2. Sunlight on a white diffuse surface observed at point blank is 7mW/cm*2.
Lets calculate how much light enters the eye at 2ft distance:
Diffuse Reflection = 5% reflectivity, the inverse square law says that double the distance = half the intensity, 0.5(0.05*15mW) = ~0.375mW/cm*2 entering the eye. This kind of irradiance is definitely not hazardous. Apply that formula to direct sunlight diffusely reflected results in 3.5mW/cm*2, nearly 10x as powerful. Now, when this happens with sunlight your eyes react because they are far more sensitive to the full spectrum than to single band NIR radiation. However, red hot metal (and fire) actually emits NIR radiation 700-890nm, which is visible but does not cause dilation of the pupils. As a welder I've stared for hours at red hot steel pouring off so much NIR that a 3 square foot area is bathed in light. The heat can be felt on the eyes and skin from feet away enough to be physically uncomfortable form tissue heating. imagine being very very close to a camp fire, your skin gets hot and your eyes dry but the fire isn't nearly too bright to look at. I'd say the intensity is double to perhaps quadruple that of direct sunlight, so figure 450mW/cm*2. Apply the same 2ft distance with equally as tremendous divergence a similar formula may be used. However, keep in mind that in the case of fire and hot metal you are staring DIRECTLY at it, so no 5% from diffuse reflection. The light is diffuse, but not reflected. This results in 225mW/cm*2. This is 600 times as intense as the light coming out of my 808nm NIR Laser. If the diffuse reflection from my laser can hurt your eyes, than I don't see how I'm not blind from work. There is a lot of IR mixed in with the NIR from work, but its still getting in just like the NIR. The point is that thousands of workers are exposed to intensities of NIR and IR in diffuse form hundreds of times more intense than the IR coming out of Laser Pointers.
***It should be noted that given the same intensity and exposure all light with the exception of UV is equally as dangerous no matter the wavelength. Exposure is reduced for visible wavelengths compared to invisible ones because of pupillary responce. ALL DIRECT (OR SPECULAR) OCCULAR BEAM EXPOSURE IS HIGHLY HAZARDOUS ABOVE 5mW/cm*2***
Eye Damage:
Eye damage happens in two ways: Intraoccular Heat-Related Tissue Destruction (burning the inside of your eyes) and Receptor Cell Overstimulation (flash blinds).
IR:
As true IR is invisible it can not cause Receptor Cell Overstimulation, so the only damage it could cause would be heat damage. Normal irradiance calculations would apply. The ONLY reason IR would be more dangerous than NIR is because there would be no pupillary response so there is greater risk in accidental direct exposure.
NIR:
I am curious to find out if it is really as dangerous as hype suggests it to be, NIR is emitted in large quantities by many many everyday items. In the case of pointer lasers it is often 808nm, which is rather visible. I have been VERY cautious with my new 150-200mW 808nm burner as I'd say it looks as bright as 1mW 670nm. I realize that specular reflections and direct beam exposure is a tremendous hazard, but what about diffuse reflections from >2ft. The beam has a HUGE divergence (something like 75mRad), so diffuse reflections of a spot 10cm+ in diameter shouldn't be harmful, right? 10cm*2 of 150mW = 15mw/cm*2. Sunlight on a white diffuse surface observed at point blank is 7mW/cm*2.
Lets calculate how much light enters the eye at 2ft distance:
Diffuse Reflection = 5% reflectivity, the inverse square law says that double the distance = half the intensity, 0.5(0.05*15mW) = ~0.375mW/cm*2 entering the eye. This kind of irradiance is definitely not hazardous. Apply that formula to direct sunlight diffusely reflected results in 3.5mW/cm*2, nearly 10x as powerful. Now, when this happens with sunlight your eyes react because they are far more sensitive to the full spectrum than to single band NIR radiation. However, red hot metal (and fire) actually emits NIR radiation 700-890nm, which is visible but does not cause dilation of the pupils. As a welder I've stared for hours at red hot steel pouring off so much NIR that a 3 square foot area is bathed in light. The heat can be felt on the eyes and skin from feet away enough to be physically uncomfortable form tissue heating. imagine being very very close to a camp fire, your skin gets hot and your eyes dry but the fire isn't nearly too bright to look at. I'd say the intensity is double to perhaps quadruple that of direct sunlight, so figure 450mW/cm*2. Apply the same 2ft distance with equally as tremendous divergence a similar formula may be used. However, keep in mind that in the case of fire and hot metal you are staring DIRECTLY at it, so no 5% from diffuse reflection. The light is diffuse, but not reflected. This results in 225mW/cm*2. This is 600 times as intense as the light coming out of my 808nm NIR Laser. If the diffuse reflection from my laser can hurt your eyes, than I don't see how I'm not blind from work. There is a lot of IR mixed in with the NIR from work, but its still getting in just like the NIR. The point is that thousands of workers are exposed to intensities of NIR and IR in diffuse form hundreds of times more intense than the IR coming out of Laser Pointers.
