200 mw green laser

200 mw green laser - safe?

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200 mw green laser - safe?
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Rich Grise
Guest

Posted: Tue Feb 08, 2005 8:40 am Post subject: Re: 200 mw green laser - safe?

On Sun, 06 Feb 2005 17:29:07 -0800, Chris Carlen wrote:

Quote:

Oddly, a few days later I discovered that the spot in my eye simply
vanished. I cannot find that black dot anymore. I really don't know if
it means that the damage was not permanent and the retinal receptors
recovered, or if there was permanent damage and the brain simply marked
that data as "bax pixels" and now interpolates over those receptors to
give the perception of an uninterrupted image.

I wouldn't be a bit surprised - probably a lot like the blind spot where
your optic nerve joins your retina:
http://faculty.washington.edu/chudler/chvision.html

Quote:

The brain's signal processing is extremely sophisticated!

Yup!

Cheers!
Rich

Sam Goldwasser
Guest

Posted: Tue Feb 08, 2005 8:40 am Post subject: Re: Eyeball Damage - 200 mw green laser - safe?

Mark Jones <abuse@127.0.0.1> writes:

Quote:

Sam Goldwasser wrote:
Mark Jones <abuse@127.0.0.1> writes:

Perhaps the inversion caused by the iris allows the laser light to "burn" part
of the macula in the center of the eye, producing a blackend line, which the
body slowly heals or it moves out of view?

Sorry, what are you trying to say? The damage from a visible collimated laser is
to the retina or its associated structures.

Well the eye is not hollow, it has some kind of goo in the center, which is not
just a clear liquid. Look at an eyeball in long-wave UV light - the inside will
glow. A family member has a macular hole in this substance, severely affecting
vision. Anyways, perhaps the iris focuses this "not too terribly bright" light
enough to BURN the goo inside the eye, leaving a thin black line going from iris
to retina. Slowly, over time, the damage is repaired.

I'm not sure if this is possible or not, just throwing out ideas. We do
understand that the lens doesn't focus all the light energy directly onto the
retina, right? There is some image-flipping going on there about 2/3rds the way
to the retina. That tightly-focussed area is where I'm talking about. The light
intensity-per-mil would be many times greater than "5mw."

That "goo" is called the "vitreous humor". Depending on age (and other
factors), may be a gel to a liquid. But, except for floaters, which
are very common, it is very clear and shouldn't absorb visible laser
light significantly at any power level we're discussing.

Even if damage to the vitreous were present, unless it was very close to
the retina, the defect would be out of focus. Even with gel, it would
move around somewhat, as do the floaters.

The light rays don't cross inside the eye for a collimated laser beam
and normally focused eye. The smallest spot and highest power density
is at the retina.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

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Rich Grise
Guest

Posted: Tue Feb 08, 2005 8:40 am Post subject: Re: Eyeball Damage - 200 mw green laser - safe?

On Mon, 07 Feb 2005 21:42:27 -0500, Mark Jones wrote:
....

Quote:

-- "If a cluttered desk is the sign of a cluttered mind, what is the
significance of a clean desk?" -- Laurence Peter

Or an empty one? ;-)

Cheers!
Rich

James Sweet
Guest

Posted: Tue Feb 08, 2005 8:40 am Post subject: Re: 200 mw green laser - safe?

"Frank Bemelman" <f.bemelmanq@xs4all.invalid.nl> wrote in message
news:4207293d$0$28993$e4fe514c@news.xs4all.nl...

Quote:

"Chris Carlen" <crobc@BOGUSFIELD.sbcglobal.net> schreef in bericht
news:cu6g940f57@news2.newsguy.com...
Greysky wrote:
I have the opportunity to purchase a green laser with an output power
of
150 - 200 milliwatts. How safe are lasers at this power level? Do I
need
to
get goggles to avoid burning out my retinas at this level, or are
accidental
flashes still harmless?

Such a laser is a menace to humanity and will definitely blow a hole
clear through your retina.

I know nothing about lasers, but would think that 200mW also
hurts/stings on normal skin, when hold still.

120mw of green does, at least at fairly close range. I'd be very hesitant to
play around with 200mW and I've been messing with lasers for years.

Rene Tschaggelar
Guest

Posted: Tue Feb 08, 2005 6:07 pm Post subject: Re: 200 mw green laser - safe?

Greysky wrote:

Quote:

I have the opportunity to purchase a green laser with an output power of
150 - 200 milliwatts. How safe are lasers at this power level? Do I need to
get goggles to avoid burning out my retinas at this level, or are accidental
flashes still harmless?

IMO, everything above 5mW is a class 1 laser, and involves
training the people, safety interlocks, removing people
from the site and such.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Pat Ford
Guest

Posted: Tue Feb 08, 2005 6:45 pm Post subject: Re: Eyeball Damage - 200 mw green laser - safe?

"Rich Grise" <richgrise@example.net> wrote in message
news:pan.2005.02.08.05.14.27.753547@example.net...

Quote:

On Mon, 07 Feb 2005 21:42:27 -0500, Mark Jones wrote:
...
-- "If a cluttered desk is the sign of a cluttered mind, what is the
significance of a clean desk?" -- Laurence Peter

Or an empty one? ;-)

Cheers!
Rich

so when I'm not at work or leave my desk, I have a vacant mind?
Pat

Sam Goldwasser
Guest

Posted: Tue Feb 08, 2005 8:37 pm Post subject: Re: 200 mw green laser - safe?

Rich Grise <richgrise@example.net> writes:

Quote:

On Sun, 06 Feb 2005 17:29:07 -0800, Chris Carlen wrote:

Oddly, a few days later I discovered that the spot in my eye simply
vanished. I cannot find that black dot anymore. I really don't know if
it means that the damage was not permanent and the retinal receptors
recovered, or if there was permanent damage and the brain simply marked
that data as "bax pixels" and now interpolates over those receptors to
give the perception of an uninterrupted image.

I wouldn't be a bit surprised - probably a lot like the blind spot where
your optic nerve joins your retina:
http://faculty.washington.edu/chudler/chvision.html

The brain's signal processing is extremely sophisticated!

Yup!

Yes, but you can find the blind spot if you look for it. If the
laser induced afterimages or whatever went away totodally, they're
gone, not interpolated out.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

Chris Carlen
Guest

Posted: Tue Feb 08, 2005 9:38 pm Post subject: Re: 200 mw green laser - safe?

Sam Goldwasser wrote:

Quote:

Rich Grise <richgrise@example.net> writes:

On Sun, 06 Feb 2005 17:29:07 -0800, Chris Carlen wrote:

Oddly, a few days later I discovered that the spot in my eye simply
vanished. I cannot find that black dot anymore. I really don't know if
it means that the damage was not permanent and the retinal receptors
recovered, or if there was permanent damage and the brain simply marked
that data as "bax pixels" and now interpolates over those receptors to
give the perception of an uninterrupted image.

I wouldn't be a bit surprised - probably a lot like the blind spot where
your optic nerve joins your retina:
http://faculty.washington.edu/chudler/chvision.html

The brain's signal processing is extremely sophisticated!

Yup!

Yes, but you can find the blind spot if you look for it. If the
laser induced afterimages or whatever went away totodally, they're
gone, not interpolated out.

But if the brain (or perhaps there is initial processing done by the
ganglia near the retina itself) wasn't interpolating, then the damaged
spots would be visible always.

I am convinced that damage at the level of a single, or a few receptors
can be interpolated so as to be invisible under most circumstances. And
at this level, is perhaps also invisible to an ophthalmologist.

Under extremely unusual circumstances, I can actually see (for only an
instant) several "dots" that look like missing pixels. These only
appear for instance if I see an out of focus point of light, and also at
a moment when the brightness level is rapidly changing or something like
that. Very unusual circumstances, as I said, but the dots are
perceptible, I think including the pointer induced "crater" shaped dot.

Also sometimes larger spots are visible more to the peripheral vision,
where I think I have been exposed to beams in the past. These can
appear for a few moments when the eyes are closed and "equilibrated" for
a while. But under 99.9% of circumstances, I can see no such dots.
These dots are also not black, but can appear as luminosity for a few
seconds against the dark noise background of the retina. Some of these
are also not perfectly round, nor do they last only an instant. So I am
convinced they are residues of past overexposures to laser beams, rather
than retinal scintillation events, which are also a known phenomenon and
appear only for an instant as very bright single dot sized "sparks."

I recall once being told by a professor who was developing photonic
materials modeled after the physical chemistry in the retina, that the
eye operates "differentially". That the eye actually *cannot see* a
static image at all! In order for the eye to maintain the perception of
an image, it must continually dither the point of view, even if we are
unaware of this dithering. The proof he said, could be partly evidenced
by attempting to look at an object without moving the eye. If you can
do it very precisely, the object will fade away and become invisible.

This is extremely difficult to do with normal vision. However, it is a
bit easier with myopia or perhaps it's opposite (what's that called?).

I have experimented with this, and indeed I can see things begin to
disappear when looking at them with very strict concentration. Also,
the harder I concentrate, the more I notice the eye desperately wanting
to dither! As soon as it dithers just a bit, the image becomes more
distinct again.

Interestingly, if you get close to being able to maintain concentration
on a point of an image, then the image while it is fading into
indistinguishability (whew! a lot of syllabilables!) begins to appear
increasingly like a photographic JPEG image being subjected to an
excessive application of sharpening.

Good day!

--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov -- NOTE: Remove "BOGUS" from email address to reply.

Pat Ford
Guest

Posted: Tue Feb 08, 2005 10:05 pm Post subject: Re: 200 mw green laser - safe?

"Chris Carlen" <crcarle@BOGUS.sandia.gov> wrote in message
news:cuame501q6s@news4.newsguy.com...

Quote:

Sam Goldwasser wrote:

snip

Quote:

I recall once being told by a professor who was developing photonic
materials modeled after the physical chemistry in the retina, that the
eye operates "differentially". That the eye actually *cannot see* a
static image at all! In order for the eye to maintain the perception of
an image, it must continually dither the point of view, even if we are
unaware of this dithering. The proof he said, could be partly evidenced
by attempting to look at an object without moving the eye. If you can
do it very precisely, the object will fade away and become invisible.

Snip

Quote:

Good day!

--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov -- NOTE: Remove "BOGUS" from email address to reply.

I used to do that in church ( very little else to do there) stare at a
candle and the rest of the world fades. Try going to church more, helps
insomina too.
Pat

John Woodgate
Guest

Posted: Tue Feb 08, 2005 10:26 pm Post subject: Re: 200 mw green laser - safe?

I read in sci.electronics.design that Chris Carlen
<crcarle@BOGUS.sandia.gov> wrote (in <cuame501q6s@news4.newsguy.com>)
about '200 mw green laser - safe?', on Tue, 8 Feb 2005:

Quote:

However, it is a
bit easier with myopia or perhaps it's opposite (what's that called?).

hypermetropia.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Don Klipstein
Guest

Posted: Wed Feb 09, 2005 2:48 am Post subject: Re: 200 mw green laser - safe?

In article <4208ab8b$0$3399$5402220f@news.sunrise.ch>, Rene Tschaggelar wrote:

Quote:

IMO, everything above 5mW is a class 1 laser, and involves
training the people, safety interlocks, removing people
from the site and such.

5 mW and above, but less than 500 mW, is Class IIIb. But the rules
sound about right.

Unless something changed in recent years, lasers 1 mW or more but less
than 5 mW are Class IIIb unless the beam characteristics are such that it
is not reasonably foreseeable for 1 mW or more to enter the eye and get
focused onto a single point on the retina, in which case the laser is
Class IIIa. However, I see many laser pointers in the 1-5 mW range
labelled as Class IIIa.

Class I visible lasers have power of less than .4 microwatt.

- Don Klipstein (don@misty.com)

Skywise
Guest

Posted: Wed Feb 09, 2005 3:32 am Post subject: Re: 200 mw green laser - safe?

Chris Carlen <crcarle@BOGUS.sandia.gov> wrote in
news:cuame501q6s@news4.newsguy.com:

<Snipola>

Quote:

But if the brain (or perhaps there is initial processing done by the
ganglia near the retina itself) wasn't interpolating, then the damaged
spots would be visible always.
Snipola

Don't forget that you have two eyes and the brain uses data
from both to perceive an image. The blind spot for each eye is
compensated for by the other eye. It's much easier to find
the blind spot with one eye closed.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy

Home of the Seismic FAQ
http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html

Sed quis custodiet ipsos Custodes?

Don Klipstein
Guest

Posted: Wed Feb 09, 2005 4:00 am Post subject: Re: 200 mw green laser - safe?

In article <slrnd0iufr.mts.don@manx.misty.com>, Don Klipstein wrote:

Quote:

In art. <4208ab8b$0$3399$5402220f@news.sunrise.ch>, Rene Tschaggelar wrote:

IMO, everything above 5mW is a class 1 laser, and involves
training the people, safety interlocks, removing people
from the site and such.

5 mW and above, but less than 500 mW, is Class IIIb. But the rules
sound about right.

Unless something changed in recent years, lasers 1 mW or more but less
than 5 mW are Class IIIb unless the beam characteristics are such that it
is not reasonably foreseeable for 1 mW or more to enter the eye and get
focused onto a single point on the retina, in which case the laser is
Class IIIa. However, I see many laser pointers in the 1-5 mW range
labelled as Class IIIa.

Class I visible lasers have power of less than .4 microwatt.

- Don Klipstein (don@misty.com)

I decided after posting this that I oughtta check to see what 21 CFR
1040.10 says nowadays...

That regulation has tables with all sorts of exposure limits for the
various laser classes.

As it turns out, visible lasers from 1 mW on up but less than 5 mW,
according to the limit based on output power is Class IIIa regardless of
power density in the beam.

However, there remains a regulatory distinction (in the USA) between
Class IIIa lasers with 2.5 or more mW/cm^2 "irradiance" (beam power
density) and ones with less. I believe the test conditions include a 7 mm
circular aperture to simulate a fairly dilated pupil of a human eye -
which means that a Class IIIa laser that cannot get .9621 mW or more
through a 7 mm diameter round hole does not require as harsh a warning
label as one that can if I read the regulation correctly.
Ones with irradiance less than 2.5 mW/cm^2 must be labelled,
"CAUTION - Laser Radiation - Do Not Stare Into Beam Or View Directly With
Optical Instruments". I have yet to see such a laser.
Class IIIa lasers with irradiance 2.5-plus mW/cm^2 must be labelled,
"DANGER - Laser Radiation - Avoid Direct Eye Exposure". This includes all
laser pointers 1-4.99 mW that I have ever seen.

I do remember back when 2 mW HeNe lasers sold by Edmund Scientific were
mentioned as Class IIIb. Looks like those are IIIa now.

- Don Klipstein (don@misty.com)

Sam Goldwasser
Guest

Posted: Wed Feb 09, 2005 4:16 am Post subject: Re: 200 mw green laser - safe?

Chris Carlen <crcarle@BOGUS.sandia.gov> writes:

Quote:

Sam Goldwasser wrote:
Rich Grise <richgrise@example.net> writes:

On Sun, 06 Feb 2005 17:29:07 -0800, Chris Carlen wrote:

Oddly, a few days later I discovered that the spot in my eye
simply vanished. I cannot find that black dot anymore. I really
don't know if it means that the damage was not permanent and the
retinal receptors recovered, or if there was permanent damage and
the brain simply marked that data as "bax pixels" and now
interpolates over those receptors to give the perception of an
uninterrupted image.

I wouldn't be a bit surprised - probably a lot like the blind spot where
your optic nerve joins your retina:
http://faculty.washington.edu/chudler/chvision.html

The brain's signal processing is extremely sophisticated!

Yup!
Yes, but you can find the blind spot if you look for it. If the
laser induced afterimages or whatever went away totodally, they're
gone, not interpolated out.

But if the brain (or perhaps there is initial processing done by the
ganglia near the retina itself) wasn't interpolating, then the damaged
spots would be visible always.

I am convinced that damage at the level of a single, or a few
receptors can be interpolated so as to be invisible under most
circumstances. And at this level, is perhaps also invisible to an
ophthalmologist.

Under extremely unusual circumstances, I can actually see (for only an
instant) several "dots" that look like missing pixels. These only
appear for instance if I see an out of focus point of light, and also
at a moment when the brightness level is rapidly changing or something
like that. Very unusual circumstances, as I said, but the dots are
perceptible, I think including the pointer induced "crater" shaped dot.

Also sometimes larger spots are visible more to the peripheral vision,
where I think I have been exposed to beams in the past. These can
appear for a few moments when the eyes are closed and "equilibrated"
for a while. But under 99.9% of circumstances, I can see no such
dots. These dots are also not black, but can appear as luminosity for
a few seconds against the dark noise background of the retina. Some
of these are also not perfectly round, nor do they last only an
instant. So I am convinced they are residues of past overexposures to
laser beams, rather than retinal scintillation events, which are also
a known phenomenon and appear only for an instant as very bright
single dot sized "sparks."

I recall once being told by a professor who was developing photonic
materials modeled after the physical chemistry in the retina, that the
eye operates "differentially". That the eye actually *cannot see* a
static image at all! In order for the eye to maintain the perception
of an image, it must continually dither the point of view, even if we
are unaware of this dithering. The proof he said, could be partly
evidenced by attempting to look at an object without moving the eye.
If you can do it very precisely, the object will fade away and become
invisible.

Yes, if you were able to actually hold your eyeballs
perfectly still, the perception of an image would go away.

Quote:

This is extremely difficult to do with normal vision. However, it is
a bit easier with myopia or perhaps it's opposite (what's that
called?).

Hyperopia.

Quote:

I have experimented with this, and indeed I can see things begin to
disappear when looking at them with very strict concentration. Also,
the harder I concentrate, the more I notice the eye desperately
wanting to dither! As soon as it dithers just a bit, the image
becomes more distinct again.

Interestingly, if you get close to being able to maintain
concentration on a point of an image, then the image while it is
fading into indistinguishability (whew! a lot of syllabilables!)
begins to appear increasingly like a photographic JPEG image being
subjected to an excessive application of sharpening.

The eye-brain system is amazing isn't it? Almost as good as Photoshop. :)

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

KIMEVANS
Guest

Posted: Wed Feb 09, 2005 4:55 am Post subject: Re: Eyeball Damage - 200 mw green laser - safe?

"Rich Grise" <richgrise@example.net> wrote in message
news:pan.2005.02.08.05.14.27.753547@example.net...

Quote:

Its a well -known fact that a clean and tidy desk is a sign of a SICK mind

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