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A quick laser question.

SquishyDave

Graduate Poster
S
Joined
May 27, 2003
Messages
1,643
Just say I had an 820nm 200mW laser. What colour would it be and would it do to my skin? And my eyes if I shined it there?

Thanks muchly.
 
820nm is in the near infrared. It wouldn't do much to your skin, but it could do severe damage to the light sensitive cells in your eye.

General warning to all, Never, Ever, shine a laser in your, or anyone else's, eye. It can cause permanent blindness.
 
wollery said:
820nm is in the near infrared. It wouldn't do much to your skin, but it could do severe damage to the light sensitive cells in your eye.

General warning to all, Never, Ever, shine a laser in your, or anyone else's, eye. It can cause permanent blindness.
Click to expand...
Thanks woollery one. Perhaps I should stick in the reason I asked. Visit here if you feel like being faintly annoyed.

http://www.laserquit.com.au

It's a quit smoking using laser acupuncture mob.

I emailed them and asked the power and wavelength of their lasers, they replied (eventually) that they were "very strange questions from a person who simply wants to give up smoking" but answered anyway. I replied I didn't find it strange to want to be informed about a possible treatment. Just shows the type of people who go there I guess, they just don't ask questions.
 
820 nm places the light in the infrared part of the spectrum. At 200 mW, it would be classified as a class III laser- shouldn't burn your skin but I wouldn't shine it in anyone's eyes.

http://www.fda.gov/cdrh/radhlth/pdf/lastblel.pdf

On page 36 you'll find the entry for 820 nm lasers for long exposures, showing the power/energy limits for class I, II, and III lasers.

Here is a link to the FDA laser product FAQ showing what those classifications mean:

http://www.fda.gov/cdrh/radhlth/laserfaq.html

ETA: Rats! beaten to the punch!
 
Flatworm said:
820 nm places the light in the infrared part of the spectrum. At 200 mW, it would be classified as a class III laser- shouldn't burn your skin but I wouldn't shine it in anyone's eyes.

http://www.fda.gov/cdrh/radhlth/pdf/lastblel.pdf

On page 36 you'll find the entry for 820 nm lasers for long exposures, showing the power/energy limits for class I, II, and III lasers.

Here is a link to the FDA laser product FAQ showing what those classifications mean:

http://www.fda.gov/cdrh/radhlth/laserfaq.html

ETA: Rats! beaten to the punch!
Click to expand...
Thanks for that. Your pdf was baffling. I'm sure I can use it to prove anything I want.
 
SquishyDave said:
Thanks for that. Your pdf was baffling. I'm sure I can use it to prove anything I want.
Click to expand...


Sorry about that. The tables show maximum intensity allowed by the FDA for class I,II, and III lasers, depending on wavelength and exposure time. If you go down to page 36 of the document (shows up as 42 of 49 in Acrobat Reader because of the introductory material), you'll find the table you need. Wavelengths are along the left, and exposure times are along the top. 820nm is the second entry from the top, and we'll probably want to use continuous exposure as a reference, so go to the far right column. You'll find 3 entries:

6.67D-5 W
NA
5.00D-1 W

The first line is the power limit for class I (6.67e-5 W = 66.7 uW). The second line says that class II limits do not apply for this wavelength for this sampling interval. The third line shows the limit for a class III laser is 500 mW.
 
Flatworm said:
Sorry about that. The tables show maximum intensity allowed by the FDA for class I,II, and III lasers, depending on wavelength and exposure time. If you go down to page 36 of the document (shows up as 42 of 49 in Acrobat Reader because of the introductory material), you'll find the table you need. Wavelengths are along the left, and exposure times are along the top. 820nm is the second entry from the top, and we'll probably want to use continuous exposure as a reference, so go to the far right column. You'll find 3 entries:

6.67D-5 W
NA
5.00D-1 W

The first line is the power limit for class I (6.67e-5 W = 66.7 uW). The second line says that class II limits do not apply for this wavelength for this sampling interval. The third line shows the limit for a class III laser is 500 mW.
Click to expand...
Thanks for that, I did find the right page, despite the page numbers differing, but just found that delightful array of numbers.

I'm going to have guess though, that this laser would have a hard time releasing endorphins. At least regular acupuncture does that.
 
I know that you can cause mental illness in cats with a laser pointer, they will chase the red spot till they drop, run up walls, trying to catch it, funny as all crap.
 
SquishyDave said:
Thanks woollery one. Perhaps I should stick in the reason I asked. Visit here if you feel like being faintly annoyed.

http://www.laserquit.com.au

It's a quit smoking using laser acupuncture mob.

I emailed them and asked the power and wavelength of their lasers, they replied (eventually) that they were "very strange questions from a person who simply wants to give up smoking" but answered anyway. I replied I didn't find it strange to want to be informed about a possible treatment. Just shows the type of people who go there I guess, they just don't ask questions.
Click to expand...

I read their website, but it isn't clear how they use the laser. I have seen several uses of lasers for stop-smoking services, but none actually point the laser into somebody's eye.

Some use them as a substitute for accupuncture needles, shining them onto the skin at specific locations, which is probably harmless with this laser.

Another strategy is to do a sort of Pink Floyd planetarium thing with spinning mirrors and a laser, as an hypnosis tool. It's like watching a living Spirograph. This laser does not shine at the patient - just at the ceiling or wall.
 
blutoski said:
I read their website, but it isn't clear how they use the laser. I have seen several uses of lasers for stop-smoking services, but none actually point the laser into somebody's eye.

Some use them as a substitute for accupuncture needles, shining them onto the skin at specific locations, which is probably harmless with this laser.

Another strategy is to do a sort of Pink Floyd planetarium thing with spinning mirrors and a laser, as an hypnosis tool. It's like watching a living Spirograph. This laser does not shine at the patient - just at the ceiling or wall.
Click to expand...
They shoot the laser at your acupuncture points. As opposed to using needles. Harmless I have no doubt, effective? Not so sure.
 
wollery said:
820nm is in the near infrared. It wouldn't do much to your skin, but it could do severe damage to the light sensitive cells in your eye.
Click to expand...

The ANSI Standard (ANSI Z136.1, American National Standard for the Safe Use of Lasers) is an accepted standard worldwise in the laser community for laser safety.

Per the standard, for this wavelength, the ocular MPE (maximum permissible exposure) is 1.7 mW / cm^2

This means that a direct beam in the eye is 100 times over the limit known to do no damage.

But, there is also an MPE for skin. The MPE for skin exposure is 350 mW / cm^2. Now this doesn't mean that a value above this will burn skin ... it means that this is a level known to produce no physiological effects.

A 200mW beam focused to a 1mm spot would produce a power density of about 25 W / cm^2

Skin exposure to laser light above the MPE level may cause thermal effects, dry skin, excema, dermatitis. I am particularly disturbed by the fact that the web site says that a patient may feel tingling during the procedure. This means that physiological effects are taking place.

-------------

Now, these values are generally used for unintentional or accidental exposure. Medical laser use, where a known benefit outweighs the possible dangers have different standards.

I don't know what the standards are for bunk.

- Timothy
 
physiological effects from infrared include heating. That's pretty much it. Heating, however, can mean a lot of things- like burning, scorching, that kind of thing, not limited to the exterior of your body I might add- a laser at 200mW can really do some damage when the spot is focused.
 
Flatworm said:
6.67D-5 W
NA
5.00D-1 W

The first line is the power limit for class I (6.67e-5 W = 66.7 uW).
Click to expand...
So D=e? If it's base ten, you should use E, since e implies that the base is... e.

Timothy said:
Skin exposure to laser light above the MPE level may cause thermal effects, dry skin, excema, dermatitis. I am particularly disturbed by the fact that the web site says that a patient may feel tingling during the procedure. This means that physiological effects are taking place.
Click to expand...
Or placebo.
 
Art Vandelay said:
So D=e?
Click to expand...
In the FORTRAN programming language, "D" is used for double-precision constants, and "E" for single-precision constants.

Art Vandelay said:
If it's base ten, you should use E, since e implies that the base is... e.
Click to expand...
Have you seen that usage anywhere? (That is, something like "2e3", with a lowercase "e", not meaning 2000?) I haven't.

I know that, for example, in the C programming language, the "e" can be either lowercase or uppercase. (Case generally matters in C. In FORTRAN, it never does, so naturally in FORTRAN the "e" can also be written in either case.)

Of course, the mathematical notation "2e3" means twice the cube of e, where e = 2.71828... . But there the "3" is written as a superscript, and the "e" is generally written in italics.
 
kedo1981 said:
I know that you can cause mental illness in cats with a laser pointer, they will chase the red spot till they drop, run up walls, trying to catch it, funny as all crap.
Click to expand...

Yeah one of those brought out the wildcat in a very nice (and stupid) persian at Trena's Mom's place. He wouldn't let us approach him for days.
 
I have a 200mW Green laser (it has an initial peak that is a bit higher). It feels hot on the skin after about 2 seconds when pressed to the skin. The reflection is too bright to hold it away from the skin. The emitted wavelength is 532nm at 200mW, but the actual diode is 808nm 1W continuous wave. As far as what it would do to your eyes, when I accidentally shine it on an object that is too close (less than 20 feet), the reflection is rather uncomfortable. This may be because the human eye is more sensitive to green light, but I can not imagine pointing this directly at someone’s eye.
 
I had laser-weld repair of the retina in one of my eyes. I didn't like it at all. It wasn't that it was really painful, just extremely uncomfortable. I couldn't stand for the doc to do it all at once, and I had a small tear.

The doofus doc points a laser in my eye then yells at me for blinking. I couldn't help it, my eye just blinked, seems like he would have known that was going to happen. After that he held my eye open.
 
AK-Dave said:
I have a 200mW Green laser (it has an initial peak that is a bit higher). It feels hot on the skin after about 2 seconds when pressed to the skin. The reflection is too bright to hold it away from the skin. The emitted wavelength is 532nm at 200mW, but the actual diode is 808nm 1W continuous wave. As far as what it would do to your eyes, when I accidentally shine it on an object that is too close (less than 20 feet), the reflection is rather uncomfortable. This may be because the human eye is more sensitive to green light, but I can not imagine pointing this directly at someone’s eye.
Click to expand...
Dave, If you don't mind, I'll run your laser info through a software program I have (may have to PM you for more data though) and see what it comes up with. I haven't used it yet, but it gives Maximum Permissible Exposure(MPE), Safe Eye Exposure Distance (SEED), Optical Density (OD) for protective eyewear, etc. IIRC.

I need a practice case, if you're game.
 
Mr. Skinny said:
Dave, If you don't mind, I'll run your laser info through a software program I have (may have to PM you for more data though) and see what it comes up with. I haven't used it yet, but it gives Maximum Permissible Exposure(MPE), Safe Eye Exposure Distance (SEED), Optical Density (OD) for protective eyewear, etc. IIRC.

I need a practice case, if you're game.
Click to expand...
I don't own a laser... Oh I see. You were talking to the imposter Dave. That's fine. You'll both rue this day.
 
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