Laser dot question

[hozone]

Hello,
I've read a few post about watching the laser dot, but i can not find the answer to my question.

I'm building an engraving machine, using a DVD-rom writer red laser. I suppose it's a 100/150mW laser almost.
Laser it is mounted on a 12x30mm 5.6mm TO-18 AixiZ housing.

Question is: is it safe to use it without safety glasses, i mean, watching the red laser dot engraving wood, or paper at almost 40cm?

I've also a less power IR CD-rom writer laser around here.

All the test was made using safety glasses, or watching laser through a webcam.

Thank you for help.

 

[busman2]

I would say that the reflective light would not be safe. Safety glasses are inexpensive especially when comparing it to what your eyesight is worth. Even if the damage was not instant you would certainly wish that you wore some later down the track when Retina damage showed up! EaglePair for the Red wavelength would do the trick!

 

[Benm]

Realistically the answer depends on how whatever you are cutting/engraving reflects the light. If it scatters it uniformly (such as white paper that is not being burned or cut does), looking at the dot would be perfectly safe at 40 cm distance, although it could become uncomfortable.

If the material reflects the light non-uniformly things can get a bit hairy though. Especially materials like plastics will melt and that can result in a smooth, reflecting (liquid) surface that reflects the light in a more or less specific direction. It is hard to predict how focussed this could be (and even what direction it goes), so it would be best to err on the safe side and observe the dot using goggles.

Be especially cautions with IR diodes like the CD rom one. Though it has less power, the light is also much less visible, and something that looks very dim could actually be quite energetic and pose a hazard you literally cannot see coming at you.

 

[OzLasers]

Yeah... it almost certainly wouldn't be safe without a shielded laser or safety equipment. I certainly wouldn't be comfortable being in a room while something like that was in operation.

You can get decent goggles cheap. Why take the risk?

 

[hozone]

Thank you,
Yes, i've glasses but i would like to give this laser engraver to a friend, i just will give my glasses too

Another silly question.
If the dot of a 100mW laser is out of focus, let's say a 2cm dot, this will not cause problem, or better, serious problem, right?

 

[busman2]

Thank you,
Yes, i've glasses but i would like to give this laser engraver to a friend, i just will give my glasses too

Another silly question.
If the dot of a 100mW laser is out of focus, let's say a 2cm dot, this will not cause problem, or better, serious problem, right?

If I took a 2Lb hammer and hit you hard on the finger with it would hurt and cause damage, but if i turned it on the side and hit you hard on the finger would it still hurt and cause damage, would you even want to try???

It is good that you are looking after your friend by giving him the glasses too!

 

[hozone]

If I took a 2Lb hammer and hit you hard on the finger with it would hurt and cause damage, but if i turned it on the side and hit you hard on the finger would it still hurt and cause damage, would you even want to try???

It is good that you are looking after your friend by giving him the glasses too!

Understaind

Thank you!

 

[Benm]

If I took a 2Lb hammer and hit you hard on the finger with it would hurt and cause damage, but if i turned it on the side and hit you hard on the finger would it still hurt and cause damage, would you even want to try???

This is power distribution of area, and with such examples things start to sound scary really quickly. The comparison between looking directly into the laser and at the diffuse dot would be something entirely different: Perhaps something like hitting you on the fingers with a ruler, versus hitting the top of a hill a nuclear bomb shelter you reside in was constructed under.

But to give it a bit of real life perspective: Say you took an 21 watt brake light from a car and powered that up - just the bulb, no reflectors or anything. You'd probably agree this would be safe to look at from half a meter distance. The filament of this bulb is roughly as big (or small) and as bright as the dot produced by a 0.5 watt visible laser on a piece of paper... and that is couting visible light -only-, not the shitload of IR that lightbulb is kicking out which you might be able to feel on your skin (or retina).

 

[busman2]

OK Benm, you have been doing this a lot longer than me. I did not feel that it would be a safe thing to do but if you feel it is ok to tell him it is safe go for it!

 

[Benm]

Safety and comfort are different things though.

While it is from any perspective perfectly eye-safe to look at, say, the dot from a 100 mW green laser on a piece of matte white paper a meter away from you, this does mean that this will be comfortable.

If you do so for a bit you might notice a bit of a negative after-image, not unlike you would after looking at sunset and then looking around you. This is purely due to the depletion of light sensitive molecules in your eyes though, and NOT a result of any permanent damage. Typically vision will recover from such things fully in 15 minutes or so.

 

[hozone]

Thank you for answers!

 

[Marco Polo]

I strongly urge the use of safety glasses whenever dealing with highly-focused laser light. I was burning cardboard with a 500mW 405nm laser at fine focus (more than a year ago), and it left a very faint bleached spot in my vision that stayed there a few days. The spot eventually faded away, luckily, and a subsequent routine eye exam revealed nothing untoward.

Viewing the infinity-focused beam is usually fine, however viewing a finely focused point is not. Put your glasses on.

 

[hozone]

Thank you for sharing your experience!