Laser, Outside, and Daytime: Safe?

[Wolfman29]

Hey there everyone.

So I recently finished my 900mA (1W or so?) 445 build, and I was shining it on the ground outside during the day.

Now, I live in central Arizona (Scottsdale), also known as the brightest ****ing place in the country. Really - it's hard to be in a room with open windows without shades, let alone be outside around noon-time.

Anyway, I was curious because the dot on my laser, while visible, was not very bright. It's still 1W, however, no matter the brightness of the ambient environment... so is the diffuse reflection from the dot, or the partial reflection of the dot, more dangerous, because we are less likely to notice and therefore blink from it? Or is it less dangerous, because our pupils are already less dilated, so less light gets into the retina?

I would think the latter, but I cannot be certain. Anyone know?

 

[GBD]

Id have to say from the ambient dot itself, it will still cause some damage if you look at it from VERY closly outside (and I mean close and for long, like a foot away, my 445nm personally doesn't bother me at all in daytime, even when its a few feet away from me), but as you said, your eye are already far less dialated to deal with the ambient sunlight, so from a distance I suppose it will be perfectly fine.

however, never forget that laser light is coherent amplified light, and if focused to "infinity" it will still have a great power density in its beam, so a direct hit to the eye will cause severe damage, daylight or not.

 

[Wolfman29]

Of course. Was referring to reflections and diffusions.

 

[millirad]

Yeah, spectral reflections from your laser are hazardous regardless of having a reduced sized pupil(constricted) due to sunlight. A strong hit from your laser will indeed cause damage. So you are right in thinking that bright sunshine may fool you into making a mistake. Be safe and keep your laser eyewear on.

 

[123splat]

The dot is just as bright in the sunlight as it is in a dark room at nidnight. It is what your brain does with relative contrasts between the ambient and the dot, as detected by your eyes, that lets you percieve the brightness. Same with beam and any reflections/backsplatter.

 

[Wolfman29]

@millirad
Well, yes - direct reflections are just as dangerous. However, I am thinking that diffusions from a 1W laser, while normally much more dangerous up close, are possibly less so because the pupils are less dilated. Therefore, there is less surface area for the light to enter the eye.

@123splat
As I have been mentioning, I think it is also related to the size of the pupil. While yes, there is an effect from relative contrasts, our eyes are also seeing less of the dot because our pupils are more constricted.

 

[123splat]

Pupils are constricted because of ambient light levels, but you are less likely to perceive the hazard (and thus blink or shy away from), because your brain does not 'notice' the hazard as such. The human eyes and the associated nervous system are wonderous creations, but from a comparrisons view (with electronics, for example), make for really lousy detection and response systems.

It is a good question to get the neurons boiling, though.

 

[Wolfman29]

Aye, 'tis!