Imagine I have a lamp (incoherent light - lets say it's a consumer projector), and a class 2m laser device, and both have identical divergence and identical waist width, and are kicking out the same radiant flux, all in the visible spectrum (say around 532nm).
My question: In this case, is the laser more dangerous than the projector? Why?
=====Background info=====
I often hear that the laser will be more dangerous because the light is coherent. But when I ask why, I often hear that coherence means you can focus the beam to a smaller point. But when we're already dealing with a beam that isn't focused to a point, I don't see why that would make any difference. I'm sure I'm missing something, I just don't know what!
=====Why I care=====
I care because I'm working on an invention that needs a very bright light source with a similar divergence and waist with as a consumer projector, but that needs to be a very narrow wavelength. Because of the narrow wavelength requirement, I've opted for a laser. I've done experiments with something like a laser genetics ND3, which works well, but isn't bright enough, and my concern is that if I go much brighter, it will exceed the limit for a 2m laser (which is not an option - the invention will be a consumer device). The ND3 is a 2m laser with a 40mw diode. Assuming that a 532nm diode creates ~600 lumens per watt, that equates to about 24 lumens, which isn't much. On the other hand, a laser projector (which as I understand it uses a diffuser to make the laser light incoherent) can be 10,000 lumens and still be in risk group 2, which approximately equates to class 2m for lasers (i.e. there's no risk of eye damage due to aversion responses). The ND3 has a similar size lens that the light escapes from as a projector, and a similar divergence. If you put your eye right up to the projector, or the ND3, it seems to me there wouldn't be much difference in terms of the % of the total beam entering your eye, and the divergence of that beam - only the projector is 10,000 lumens, and the ND3 is 24. Does that mean I could have a 10,000 lumen version of the ND3 and it still be class 2m?
Obviously if I opted for a more traditional light source, then I'd have to filter it down to a narrow wavelength, and throw most of the light away - but if I did this instead, would it be safer than the laser version? If so, why?
Finally, if there is some reason why laser light is inherently more dangerous than the same flux level of 'normal' light, is there some way to remove this without altering the wavelength?
Sorry about all the questions, and thanks - I'm a real beginner so any help would be amazing!
My question: In this case, is the laser more dangerous than the projector? Why?
=====Background info=====
I often hear that the laser will be more dangerous because the light is coherent. But when I ask why, I often hear that coherence means you can focus the beam to a smaller point. But when we're already dealing with a beam that isn't focused to a point, I don't see why that would make any difference. I'm sure I'm missing something, I just don't know what!
=====Why I care=====
I care because I'm working on an invention that needs a very bright light source with a similar divergence and waist with as a consumer projector, but that needs to be a very narrow wavelength. Because of the narrow wavelength requirement, I've opted for a laser. I've done experiments with something like a laser genetics ND3, which works well, but isn't bright enough, and my concern is that if I go much brighter, it will exceed the limit for a 2m laser (which is not an option - the invention will be a consumer device). The ND3 is a 2m laser with a 40mw diode. Assuming that a 532nm diode creates ~600 lumens per watt, that equates to about 24 lumens, which isn't much. On the other hand, a laser projector (which as I understand it uses a diffuser to make the laser light incoherent) can be 10,000 lumens and still be in risk group 2, which approximately equates to class 2m for lasers (i.e. there's no risk of eye damage due to aversion responses). The ND3 has a similar size lens that the light escapes from as a projector, and a similar divergence. If you put your eye right up to the projector, or the ND3, it seems to me there wouldn't be much difference in terms of the % of the total beam entering your eye, and the divergence of that beam - only the projector is 10,000 lumens, and the ND3 is 24. Does that mean I could have a 10,000 lumen version of the ND3 and it still be class 2m?
Obviously if I opted for a more traditional light source, then I'd have to filter it down to a narrow wavelength, and throw most of the light away - but if I did this instead, would it be safer than the laser version? If so, why?
Finally, if there is some reason why laser light is inherently more dangerous than the same flux level of 'normal' light, is there some way to remove this without altering the wavelength?
Sorry about all the questions, and thanks - I'm a real beginner so any help would be amazing!
