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What am I seeing?

thestug

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I've noticed that if I look at an unfocused beam on any surface, that I see little specks or fuzzies on the light cast onto that surface. I should note that I'm not talking about specks in the beam (which I think are just caused by dust and impurities in the air), but the dot on the wall looks almost like the static on a TV. I only ask, because I was showing a friend a laser and he asked me why the unfocused dot looked "fuzzy". Up until that point, I though it was just my eyes playing tricks on me.

I tested my vision on a flashlight with no hotspot in the center, but none of these fuzzies occur. So what am I seeing and why?
 

Laser Chick

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When the beam is flared wide, one thing could be impurities in the lens. You are taking a very small part of the lens and then casting it onto a surface at hundreds if not thousands of times wider so it shows any imperfection. Sort of like the laser through a drop of pond water experiment.
Another aspect is purple (405nm) messes with many peoples eyes as it is so close to the end of the visible spectrum.
 

thestug

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When the beam is flared wide, one thing could be impurities in the lens. You are taking a very small part of the lens and then casting it onto a surface at hundreds if not thousands of times wider so it shows any imperfection. Sort of like the laser through a drop of pond water experiment.
Another aspect is purple (405nm) messes with many peoples eyes as it is so close to the end of the visible spectrum.
I don't think it's the lens since the lens was removed from the laser. Unless there's also a lens on the can of the diode? Typically if my lens is dirty I see splotches, but they generally move if turn the laser and are generally a lot larger than the "static" that I'm seeing.

Now that you mention it, my 405nm laser does show this effect the best. However, even 532nm still has the same effect just not as bad.
 

Laser Chick

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Not many parallel light sources give a pure smooth output unless the price point is up there or lenses correct it. That is correct, I am not talking about dirt/oil on the lenses but in the lens material itself. Not sure if all cans have a lens/glass on the face/front of them.
 
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My 405 does weird stuff and haven't found a reason why. My 405 looks like 4 dots in a square shape but hen I put my safety glasses on it appears a a single spot. So Its not a TEM thing. I don't know why it does this.
 
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Laser Chick

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Plus with 405nm it seems to change when you point it at different colored surfaces. When I go from a dark brown couch, to a maple colored floor to a white ceiling it goes from having a halo, to looking like a spider/star to a fuzzy dot.
 

Eudaimonium

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I've noticed that if I look at an unfocused beam on any surface, that I see little specks or fuzzies on the light cast onto that surface. I should note that I'm not talking about specks in the beam (which I think are just caused by dust and impurities in the air), but the dot on the wall looks almost like the static on a TV. I only ask, because I was showing a friend a laser and he asked me why the unfocused dot looked "fuzzy". Up until that point, I though it was just my eyes playing tricks on me.

I tested my vision on a flashlight with no hotspot in the center, but none of these fuzzies occur. So what am I seeing and why?
I'm thoroughly amazed and disappointed over the replies given so far. It's like we're on the wrong forum.

It's not lens impurities or whatever.

It's called "destructive interference" caused by surface irregularities, when shined with very narrow spectrum light such as a laser. Phenomenon has been called "fuzzyness, speckles, noisy..." and it's easily googlable. In fact first few results on google are from LPF of people asking the same question with disturbing regularity.

https://en.wikipedia.org/wiki/Speckle_pattern

Class dismissed for today. Tomorrow I want your assignments on "Why lasers are awesome" on my desk.

My 405 does weird stuff and haven't found a reason why. My 405 looks like 4 dots in a square shape but hen I put my safety glasses on it appears a a single spot. So Its not a TEM thing. I don't know why it does this.
I would see a doctor about that. This can't be normal. To me, the 405nm dot simply appears much larger than it normally is, which neatly corresponds with refraction of short wavelengths on eye's lens.

If you are having any sort of image duplication in your vision, it could be a sign of something worse down the line.
 

Laser Chick

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:worthy: :worthy: :worthy: :worthy: :worthy: :worthy:

Okay Eudaimonium, I used the word "in" instead of "on"
The surface of the glass is still part of the glass the last time I checked so yes the information given is correct as I meant for it to encompass all of the glass.

imperfection/irregularities = pretty much the same beast.

When Mama calls you tonight and says "Dinner" is ready. You prefer it called "Supper"
So no "Supper" for you tonight young man, off to your room!!! :p :na: :na: :na: JK :D :D
 

diachi

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:worthy: :worthy: :worthy: :worthy: :worthy: :worthy:

Okay Eudaimonium, I used the word "in" instead of "on"
The surface of the glass is still part of the glass the last time I checked so yes the information given is correct as I meant for it to encompass all of the glass.

imperfection/irregularities = pretty much the same beast.

When Mama calls you tonight and says "Dinner" is ready. You prefer it called "Supper"
So no "Supper" for you tonight young man, off to your room!!! :p :na: :na: :na: JK :D :D
Not necessarily just surface irregularities on your optics though - surface irregularities on any surface you point the laser on will have the same effect. Such as reflections from a matte wall or piece of matte plastic. I think that may be what Eudaimonium was getting at. :)
 

Gabe

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I know exactly what OP is talking about, and I was baffled too. Thanks Eudamonium!
 

bobhaha

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New kids on the block need some learning to do :na:

I'm thoroughly amazed and disappointed over the replies given so far. It's like we're on the wrong forum.

It's not lens impurities or whatever.

It's called "destructive interference" caused by surface irregularities, when shined with very narrow spectrum light such as a laser. Phenomenon has been called "fuzzyness, speckles, noisy..." and it's easily googlable. In fact first few results on google are from LPF of people asking the same question with disturbing regularity.

https://en.wikipedia.org/wiki/Speckle_pattern

Class dismissed for today. Tomorrow I want your assignments on "Why lasers are awesome" on my desk.



I would see a doctor about that. This can't be normal. To me, the 405nm dot simply appears much larger than it normally is, which neatly corresponds with refraction of short wavelengths on eye's lens.

If you are having any sort of image duplication in your vision, it could be a sign of something worse down the line.
 

thestug

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I'm thoroughly amazed and disappointed over the replies given so far. It's like we're on the wrong forum.

It's not lens impurities or whatever.

It's called "destructive interference" caused by surface irregularities, when shined with very narrow spectrum light such as a laser. Phenomenon has been called "fuzzyness, speckles, noisy..." and it's easily googlable. In fact first few results on google are from LPF of people asking the same question with disturbing regularity.

https://en.wikipedia.org/wiki/Speckle_pattern

Class dismissed for today. Tomorrow I want your assignments on "Why lasers are awesome" on my desk.
Thanks for the explanation. Atleast I know, that my eyes aren't playing tricks on me now.
 
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Possibly my eyes may be off. My eyes take a beating everyday at work staring at very complex shapes and lines under technical lighting for up to 6 hours at a time 5 days a week for 21 years now. At the end of my work day my eyes have trouble focusing on anything further than an arms reach. But, I don't understand why this only happens with my 405. No other lasers I have look this way. It's not even faint it's pretty distinctively 4 dots and my wife also sees the same thing so it will remain a mystery I guess.
 

Eudaimonium

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Not necessarily just surface irregularities on your optics though - surface irregularities on any surface you point the laser on will have the same effect. Such as reflections from a matte wall or piece of matte plastic. I think that may be what Eudaimonium was getting at. :)
Yes, that. The surface illuminated by the laser (optics are irrelevant in respect of this phenomenon) is what I meant.

The surface which diffuses the light creates multiple "wavefronts" as described within Wiki article. It just so randomly happens that some wavefronts exhibit destructive interference between themselves when they finally reach your eyes.

@LaserChick, FYI I don't eat supper, and am not at home with my parents, AND with what's said above, your analogy is a bit off :p
 




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