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Safety question about 5mW red laser (eyes itching)

julien

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Hello, I am new to the forum and have an important safety question. I have read many laser safety manuals and guides online prior to ordering my laser, so I know the basics and some of the advanced, please no pointing out obvious things like "don't shine the laser directly into your eye". Also please read my entire question before replying, thanks.

Two days ago I received a 5mW red laser pointer that I had bought on ebay two weeks prior. It was labled as a 5mW laser on ebay, shipped from hong kong, and only cost me approx $3. I bought this laser for presentations and also as a toy for my laser dot obsessed cat.

The item page is Red Powerful Laser Pointer Pen Beam Light 5mW New - eBay (item 350145195200 end time Sep-16-10 17:14:23 PDT)

I have been playing around with the pointer today, mostly just shining it at the wall for my cat to jump at, and I have noticed that after looking at the dot for a while my eyes begin to itch.

Now I'm starting to worry about the safty of this laser. Is it normal for low powered lasers to make your eyes itch from looking at the dot? More importantly, can looking at the dot of a 5mW laser do any damage. (assuming the dot is AT LEAST 1 foot away)


The following is to give a better idea of the lasers' brightness.

Indoors with low lighting I have tried shining the dot at my hand and it is bright to the point where it is uncomfortable to look at. Shining the dot at a white or beige wall (or wooden floor) several meters away makes it tolerable, but still bright. Shining the dot outdoors on the ground or indoors on a patch of sun at noon the dot looks quite dim, only adding a small red colouring.

Laser Specs

advertised as 5mW
made in hong kong
standard red laser pen using two AAA batteries
one laser diode in small aluminum chamber
no focusing lense so dot is quite large at a distance (approx 2mm at 1ft, 2 cm at 7-8m, and several inches when shining at a tree or at the ground in my neighbours yard)


I had the same problem yesterday but put the problem down to dust and tiredness. Today the same thing happened after looking at the dot for a while (mostly from 2-9m away for 10-15 min while playing with cat). I've looked up details on the net but can only find articles refering to looking at >= 100mW laser dots.

My eyes will begin to itch mildly after looking at the pointer dot for several minutes (again I have to state that this is while playing with my cat. I keep moving the dot and constantly switch the pointer on and off when my cat's face gets too close.) , this effect mostly dissapates within 15-20 min but lingers very slightly for about an hour. It is darkish indoors so pupils are mostly dilated. (on a white wall across the room the dot is uncomfortable to look at directly for more than a few seconds, when I shine it at a patch of sunlight near my feet the dot looks much dimmer, and doesn't look too bright)

So final question, Does anyone know why looking at the pointer dot makes my eyes itch, is this normal, and is it dangerous and/or damaging in any way.

I have read that red lasers have a dedicated diode and produce no IR, so I have ruled that out. I might be wrong though.

Thank you for your time.
 

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I will point out one possibility: it may be overspec. Being overspec, or putting out more power than listed is common for green and violet, not so much for red but it is possible. If this is an overspec laser then it wouldn't be surprising that it's uncomfortable.

Seeing as pointers >5mW can't legally be imported to the US, I could easily see an eBay seller advertising them as being lower powered to sell in the US. Once again, this isn't common for red, but it could happen.

Other members that work with red more might be able to guess the power from your description; I don't work with it enough to be confident. Without using a propper power meter, there's no way to know for sure what the output really is.
 

RA_pierce

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I have one just like that.
It is a piece of junk. Build quality sucks. :D
It outputs about 10mW max with fresh batteries. Most cheap reds I've played with are around 5-10mW.

Your eyes will be fine.
The "itchiness" you describe is not likely caused by the laser.
Avoid direct exposure.
 
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julien

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I will point out one possibility: it may be overspec. Being overspec, or putting out more power than listed is common for green and violet, not so much for red but it is possible. If this is an overspec laser then it wouldn't be surprising that it's uncomfortable.

Seeing as pointers >5mW can't legally be imported to the US, I could easily see an eBay seller advertising them as being lower powered to sell in the US. Once again, this isn't common for red, but it could happen.

Other members that work with red more might be able to guess the power from your description; I don't work with it enough to be confident. Without using a propper power meter, there's no way to know for sure what the output really is.
Thanks. I don't think it is way overspec; if it is though as I said, if I point it at a patch of sun they seem to have similar brightness (the dot doesn't stand out from the surrounding light by a large amount). Would uploading a photo help?
 

julien

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I have one just like that.
It is a piece of junk. Build quality sucks. :D
It outputs about 10mW max with fresh batteries. Most cheap reds I've played with are around 5-10mW.

Your eyes will be fine.
The "itchiness" you describe is not likely caused by the laser.
Avoid direct exposure.
Thanks, am definetely trying to aviod direct exposure, for me, my family, and my cat. (although I'm starting to think I should get a separate <1mW laser for kitty though). 5mW or 100; the damn thing doesn't even have a focusing lense! at 40m the dot is over 2ft in diameter! XD

BTW probably normal, but the bright dot makes it take a few min extra for my eyes to adjust to darkness afterwards.

Its probably a psychological issue.
Hah Hah! maybe, but I doubt it. It probably has nothing to do with the problem but I should mention that I have above average eyesight and mild photosensitivity. (I still shouldn't be getting itchy eyes from a 5mW red laser dot though)
 
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julien

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Well since people keep suggesting it might be over spec then I shall have to stop letting my cat play with it. :(

Here are some quick photos I took. The first one is on a white wall, second ones are on a light blue wall with the laser dot projected next to a 60w eqv CFL inside a fixture, last images are with the lighs off. all images except for the darkness ones were taken with a single bulb turned on for lighting. last darkness picture was taken with camera approx 2 ft from the dot. Nasty glare right? If photos of the dot in any particular lighting situations would help anyone identify the output please drop a comment and I will try to teke the pic.

BTW I live in Canada so high powered lasers are less restricted here. (Not that i'd get one anyway if even a 5-10mW red laser dot irritates my eyes)
 

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qumefox

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It's probably just in your head... so to speak. About the only way 10mw would hurt your eyes is if you caught a direct beam in the eye. I know a lot of people complain about eye problems/headaches after looking at 405 for extended periods, but that's just because it's just hard to see and and your eyes are working hard trying to focus on the dot. I'm not sure i've ever heard of anyone having similar problems with reds.

One possibility could be that your involuntarily concentrating on the dot, and just not blinking as much as you do normally, and your eyes are drying out.
 

julien

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It's probably just in your head... so to speak. About the only way 10mw would hurt your eyes is if you caught a direct beam in the eye. I know a lot of people complain about eye problems/headaches after looking at 405 for extended periods, but that's just because it's just hard to see and and your eyes are working hard trying to focus on the dot. I'm not sure i've ever heard of anyone having similar problems with reds.

One possibility could be that your involuntarily concentrating on the dot, and just not blinking as much as you do normally, and your eyes are drying out.
That's probably it actually. Thanks. When I was playing with my cat I was trying to keep my eyes open as much as possible to avoid accidentally hitting my cat in the face with the laser dot.

On a side note, does anyone know if it is possible to fit a cheap laser pointer like this with some kind of improvised focusing lense? At 30-40 meters the dot is as big as a watermelon!:thinking:
 

qumefox

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It will have some sort of lens already. You wouldn't have a dot at all otherwise. You just need to see if you can figure out how to adjust it.
 

julien

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It will have some sort of lens already. You wouldn't have a dot at all otherwise. You just need to see if you can figure out how to adjust it.
I'm not sure, it looks like a small diode inside a small aluminum reflecting chamber. It's a bit dark and the hole is small so I might just not be seeing the lense. I any case I can't find a way to remove the cap, the manufacturer must have glued it on or something. :shhh:
 

julien

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Thanks to all of you for your time. I've also found a small trick/solution to playing with cats and lasers. If you shine the laser through your t-shirt a beam is still produced, but it only has 1/4 the intensity of the normal beam. holding the laser a cm from the fabric or applying two layers of cloth reduces the beam even more.
:lasergun:
 

mfo

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Maybe the increased activity of your cat going after the laser is making more cat dander in the ear, thus making your eyes itch.

Your eyes are fine.
 




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