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aiello

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new member here... A couple of questions for the experts:

1) blue diodes seem to be frequently harvested from projectors; what about the other colours, is there strong red and green diodes available from the same source?

2) how come reflections from high-power invisible IR lasers do not blind everyone (or cameras for that matter) nearby, even when wearing goggles?


Thanks
 



Cyparagon

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1) blue diodes seem to be frequently harvested from projectors; what about the other colours, is there strong red and green diodes available from the same source?

No. Red light is sourced from an LED, and green is sourced from a phosphor wheel, driven by the blue array. Some projectors have a green array, but it isn't as common.

2) how come reflections from high-power invisible IR lasers do not blind everyone (or cameras for that matter) nearby, even when wearing goggles?

Because the goggles protect the wearer, and the camera has an infrared filter.
 

RedCowboy

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Energy from the diffuse reflections of a fiber laser engraver are only a fraction of the lasers output, most of the energy is absorbed by the material being engraved and the energy of any diffuse reflections decreases by the square with distance, however without laser safety goggles there can be enough to damage your retinas especially with prolonged and/or occupational use and as some materials can be highly reflective wearing the goggles is a must do, but the diffuse reflections are simply not strong enough to burn through the goggles or be felt on your skin with normal/proper use.

If you want red and green multi modes take a look here.
 

aiello

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Ok that answers both questions!

I thought that even a tiny fraction of say 50 watts (engraver) or 1000 watts (cleaner) should do damage, but maybe IR filters reduce that enough.

Looking at a focussed spot of a visible laser can do damage, even if it is much less than 1 watt.

There's styropyro's 'tattoo remover' megawatt pulse laser that went straight through filters and killed camera sensors, but that's stupidly dangerous power.
 

RedCowboy

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Your eyes can be damaged by anything over 5mw according to the FDA but that's 5mw straight into your eye based on our 1/4 second blink reflex, not a diffuse reflection and Drakes tattoo remover is especially dangerous because it's a flash lamp pumped YAG which produces a very high power but very short duration pulse, something on the order of a million watts but for only a few nano seconds, that's a few one billionths of a second, normally around 8ns for a cheap tattoo remover so 8 one billionths of a second, it's a very short pulse however because it's so intense even the diffuse reflection can do damage, but the total energy ( joules ) of a pulse that short in duration will be absorbed by laser safety goggles designed to attenuate that wavelength without burning through.

Looking at the focused spot of a 1 watt laser on even a white surface 5 feet away is not going to do any damage to your eyes, now I wouldn't sit and stare at it and I wouldn't stand any closer than 4-5 feet from the spot on a white surface, but looking at the diffuse reflection ( scattered ) isn't going to do any damage to our eyes.........now a million watt spot, even for a very short duration, is a different story.

Now a spectacular reflection would be very dangerous so make sure the surface you shine your laser onto isn't reflective, like a chrome car bumper or a silver foil candy bar wrapper, when in doubt wear the laser safety glasses but don't fear a laser show where a multi watt spot is on the wall overhead and don't panic if someone shines a multi watt laser on the sidewalk, that diffuse reflection is not going to damage your eyes.
 

Encap

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gazer101

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IR lasers are dangerous, but so long as you wear goggles you should be fine.
This youtuber did a test on a pig eye and saw that it damaged the cornea before it burned the retina, so there's also that:
 
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RedCowboy

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If it's in an enclosure then great but many of the Chinese engraving lasers are fiber laser engravers and are bench-top open air units and the enclosure is optional, many are 1064nm but fiber lasers are available across a wide range of wavelengths such as 1030nm, 1064nm, 1080nm and 1550nm and there are more recent all diode laser engraver sources in the 445-488nm range, 1550nm is " eye-safe " meaning that wavelength doesn't pass through our cornea so diffuse reflections are not a great concern. Lasers with an emission wavelength longer than 1400nm ( 1.4um ) are considered " eye-safe "

Also the scanning fiber lasers have a pretty narrow focal length, that is the working distance from your laser heads scanning lens, usually an F-theta several inches across to your work piece has to be adjusted for each work piece, so anything that did reflect from your work piece would be well spread out by the time it reaches your eye, this is why you see people getting away without wearing safety glasses but why take a chance, that said you never put your face near the work piece and it's forbidden to look at the laser as it's engraving through a magnifying glass or optic held to your eyes.

co2_f-theta_tab1_01.jpg


 
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