LED-FX
Enlightened
Couple of cautionary tales from alt.lasers, worth reposting here:
Chris Carlen:
>>> > 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.
You don't sound very experienced with these sorts of things. It might
be wise to experiment with a lower power laser for some time before
tinkering with something like this. You need to get a feel for how
laser light scatters off things, and reflects all over the place. Then
you can improve your chances of avoiding hazardous eye exposure.
To be honest, sometimes I am a bit too cavalier about lasers, which is a
consequence of handling them too much. To give you a clue about the
danger potential of that laser, I'll tell you a story.
A few months ago I got a simple 5mW green laser pointer (1/40 of the
power of the laser you are describing). Playing around with it
haphazardously, I somehow managed to get zapped straight in the eye with
it for a fraction of a second.
I have done this MANY times with <10mW HeNe (633nm red) lasers, and
never got hurt by them. Red light mostly diffuses across the retina and
so is much less dangerous than green.
The result was that as usual, there was a dot-shaped after-image in my
vision for quite some time. Usually, a several milliwatt laser zap
after-image will disappear in a few hours.
This one appeared to do so as well. But then a few days later, I
realized that when I had my glasses off, and I looked just slightly off
angle at points of light like a candle flame from a distance, I could
see a black dot surrounded by a very faint black ring (like an impact
crater) in the out of focus image.
I thought "oh poop, this time I really went and blew out a spot in my
retina."
What happened next was that I became somewhat obsessed with noticing
this spot. But it wasn't serious enough to appear as a persistent black
hole in my field of vision. Rather, it only would reveal itself with
some effort. Like I said, by looking at an out of focus point of light,
or by looking at the edge between two regions of very different brightness.
It also became distracting to my driving, as the obsession to determine
if the spot was obscuring my vision was actually the adverse distracting
consequence of the whole thing.
I became convinced that this was likely a permanent, though very tiny
spot of damage to my retina. I began to question whether I really
wanted to continue with the hobby of working with lasers. My job
entails working with lasers that are ridiculously dangerous, and because
of my general difficulties with maintaining concentration, I have been
seeking to work with them less and less over time as well as becoming
more and more diligent about following strict safety precautions.
But my home lasers which are "just" little CW green and red lasers, I
still tend to handle in a loose manner. I also hesitate to spend $150
on goggles. Though, the 150mW green laser that I possess (not the one
that dinged my eye) can be turned down to a very low power, and so can
actually be used more safely than a 5mW laser pointer.
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.
The brain's signal processing is extremely sophisticated!
So the point, in summary, is this:
1. A laser over 5mW, particularly a green laser of 200mW, is definitely
dangerous.
2. You won't completely blind yourself in one flash if you look into
such a laser, as the eye focusses the beam into a tiny spot so that the
damage is actually restricted to only a very small area. But if you
were to sweep your vision at the same time as a 200mW laser beam entered
your eye, it is likely that the beam would sweep a line of damage across
your retina.
3. You should consider starting with a <=5mW laser, perhaps a red HeNe
or something, in order to get familiar with laser light and its
interactions with various types of reflective surfaces.
4. Do not point any laser at any person under any circumstances! I
would avoid pointing it out of a closed room at all, just to avoid any
sort of trouble, particularly as described below. Later, if you get
interested in the subject of laser shows after having developed some
experience and understanding, you can begin to make sensible judgements
about how to display lasers safely.
5. Whatever you do, DO NOT point that laser out the window into the sky
if there is any likelyhood of illuminating an aircraft. Actually just
don't point the thing outside at all. There is an increasing atmosphere
of paranoia and hype concerning the dangers of even small lasers to
aircraft. To be clear, these lasers ARE dangerous to aircraft, but not
to the degree that some of the news reports are making it sound. And
unfortunately, people are being subjected to the possibility of legal
consequences that may far outweigh the actual damage done in several
incidents.
Good day!
--
_____________________
Christopher R. Carlen <<<
on goggles Doug Dalmage:
>>>Well, I was running a small commercial holography lab. I had a very, very
light tight darkroom, as well as it being about a class 100 cleanroom, so
there were no air particulates to show any beams in open air. My air table
consisted of a Melles Griot flat panel optical platform. Not an air table top,
but just a nice 4x5x2 inch thick panel tapped with 1/4-20 holes on 1 inch
centers. This whole thing sat on a steel framework, which then sat on top
of a bunch of innertubes, and was fairly stable. Unfortunately, the height
of all this put the working surface at just about chest height for me, so I
had to use a small step stool to reach across the table, etc. I had a SP
164 argon laser with a temp. controlled etalon, and with the current cranked
up to about 50%, I was getting about 2 watts on either the 514 or 488 line,
normally using the 514 line. I was shooting split beam transmission masters,
so the appr. 2 watt beam was sent to a variable density beam splitter where
I could alter the object/ref. power ratio. I had a small 90/10 beamsplitter
on each arm of the beam after the split, with the sampled 10% going to it's
own power meter, so I could measure and log my power ratios to get the
best exposures. I was using combinations of bolt down and mag mounts
for my components, and the setup worked fairly well for what I was doing
at that time.
One after noon, I had gotten a custom made, off axis collimating
mirror so that I could do some larger exposures, and I had set up everything
to accomodate this. I had a Newport timed electronic shutter at the output
of the 164, and I always had my goggles hanging around my neck, and would
put them on once I had a plate loaded and was ready to hit the shutter
release. On this particular setup, I wanted to do an overall power measurement
at the plate holder, so I left the plate out and put a power meter sensor in
that plane. I turned out the room lights, gave myself a good minute to let
my eyes get used to the dark, as well as to let everything settle down, and
then put on my goggles and opened the shutter. I looked at the meter that
was measuring the power at the plate holder, and it seemed to be awfully
low. I looked at the laser supply, and it was where it was supposed to be
and a quick glance of the table looked ok. At that point, I lifted up my
goggles to try and get a better view of things, and BLAM!, I got hit right in
my right eye with the full power of one leg of the beam path. What had
happened was that one of the mag holders had not grabbed, or I had not
twisted the lock enough, and that turning mirror had nudged out of the
beam path, and the raw beam before it went to the spacial filter hit me
square in the eye. It felt like I had about 100 of those big screw in
flashlamps go off at the same time, and I seem to remember being
disoriented enough that I kinda fell backwards and into the corner of
the room. Needless to say, I couldn't see a thing, and I started to pound
on the wall for the guys next door to come open the door for me, which
they did. I spent the next 3 days with a full bore "screamer" migraine,
for those of you that get migraines, you know what the screamers are
like. The Optho guy at the hospital confirmed the burn, and I just basically
laid in bed, pumped full of demerol for the eye/headache for about 3-4
days, and then for the rest of that year, I went through about 4 different
eyeglass prescriptions while the burn "healed", or settled down. It was
not a fun experience, and I still believe that had I not been wearing those
goggles, I would have not allowed myself to get into such a position as
to let a beam hit me square in the face..
Anyway, that's the story...
Just my $.02
Doug <<<<
Take Care
Adam
Chris Carlen:
>>> > 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.
You don't sound very experienced with these sorts of things. It might
be wise to experiment with a lower power laser for some time before
tinkering with something like this. You need to get a feel for how
laser light scatters off things, and reflects all over the place. Then
you can improve your chances of avoiding hazardous eye exposure.
To be honest, sometimes I am a bit too cavalier about lasers, which is a
consequence of handling them too much. To give you a clue about the
danger potential of that laser, I'll tell you a story.
A few months ago I got a simple 5mW green laser pointer (1/40 of the
power of the laser you are describing). Playing around with it
haphazardously, I somehow managed to get zapped straight in the eye with
it for a fraction of a second.
I have done this MANY times with <10mW HeNe (633nm red) lasers, and
never got hurt by them. Red light mostly diffuses across the retina and
so is much less dangerous than green.
The result was that as usual, there was a dot-shaped after-image in my
vision for quite some time. Usually, a several milliwatt laser zap
after-image will disappear in a few hours.
This one appeared to do so as well. But then a few days later, I
realized that when I had my glasses off, and I looked just slightly off
angle at points of light like a candle flame from a distance, I could
see a black dot surrounded by a very faint black ring (like an impact
crater) in the out of focus image.
I thought "oh poop, this time I really went and blew out a spot in my
retina."
What happened next was that I became somewhat obsessed with noticing
this spot. But it wasn't serious enough to appear as a persistent black
hole in my field of vision. Rather, it only would reveal itself with
some effort. Like I said, by looking at an out of focus point of light,
or by looking at the edge between two regions of very different brightness.
It also became distracting to my driving, as the obsession to determine
if the spot was obscuring my vision was actually the adverse distracting
consequence of the whole thing.
I became convinced that this was likely a permanent, though very tiny
spot of damage to my retina. I began to question whether I really
wanted to continue with the hobby of working with lasers. My job
entails working with lasers that are ridiculously dangerous, and because
of my general difficulties with maintaining concentration, I have been
seeking to work with them less and less over time as well as becoming
more and more diligent about following strict safety precautions.
But my home lasers which are "just" little CW green and red lasers, I
still tend to handle in a loose manner. I also hesitate to spend $150
on goggles. Though, the 150mW green laser that I possess (not the one
that dinged my eye) can be turned down to a very low power, and so can
actually be used more safely than a 5mW laser pointer.
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.
The brain's signal processing is extremely sophisticated!
So the point, in summary, is this:
1. A laser over 5mW, particularly a green laser of 200mW, is definitely
dangerous.
2. You won't completely blind yourself in one flash if you look into
such a laser, as the eye focusses the beam into a tiny spot so that the
damage is actually restricted to only a very small area. But if you
were to sweep your vision at the same time as a 200mW laser beam entered
your eye, it is likely that the beam would sweep a line of damage across
your retina.
3. You should consider starting with a <=5mW laser, perhaps a red HeNe
or something, in order to get familiar with laser light and its
interactions with various types of reflective surfaces.
4. Do not point any laser at any person under any circumstances! I
would avoid pointing it out of a closed room at all, just to avoid any
sort of trouble, particularly as described below. Later, if you get
interested in the subject of laser shows after having developed some
experience and understanding, you can begin to make sensible judgements
about how to display lasers safely.
5. Whatever you do, DO NOT point that laser out the window into the sky
if there is any likelyhood of illuminating an aircraft. Actually just
don't point the thing outside at all. There is an increasing atmosphere
of paranoia and hype concerning the dangers of even small lasers to
aircraft. To be clear, these lasers ARE dangerous to aircraft, but not
to the degree that some of the news reports are making it sound. And
unfortunately, people are being subjected to the possibility of legal
consequences that may far outweigh the actual damage done in several
incidents.
Good day!
--
_____________________
Christopher R. Carlen <<<
on goggles Doug Dalmage:
>>>Well, I was running a small commercial holography lab. I had a very, very
light tight darkroom, as well as it being about a class 100 cleanroom, so
there were no air particulates to show any beams in open air. My air table
consisted of a Melles Griot flat panel optical platform. Not an air table top,
but just a nice 4x5x2 inch thick panel tapped with 1/4-20 holes on 1 inch
centers. This whole thing sat on a steel framework, which then sat on top
of a bunch of innertubes, and was fairly stable. Unfortunately, the height
of all this put the working surface at just about chest height for me, so I
had to use a small step stool to reach across the table, etc. I had a SP
164 argon laser with a temp. controlled etalon, and with the current cranked
up to about 50%, I was getting about 2 watts on either the 514 or 488 line,
normally using the 514 line. I was shooting split beam transmission masters,
so the appr. 2 watt beam was sent to a variable density beam splitter where
I could alter the object/ref. power ratio. I had a small 90/10 beamsplitter
on each arm of the beam after the split, with the sampled 10% going to it's
own power meter, so I could measure and log my power ratios to get the
best exposures. I was using combinations of bolt down and mag mounts
for my components, and the setup worked fairly well for what I was doing
at that time.
One after noon, I had gotten a custom made, off axis collimating
mirror so that I could do some larger exposures, and I had set up everything
to accomodate this. I had a Newport timed electronic shutter at the output
of the 164, and I always had my goggles hanging around my neck, and would
put them on once I had a plate loaded and was ready to hit the shutter
release. On this particular setup, I wanted to do an overall power measurement
at the plate holder, so I left the plate out and put a power meter sensor in
that plane. I turned out the room lights, gave myself a good minute to let
my eyes get used to the dark, as well as to let everything settle down, and
then put on my goggles and opened the shutter. I looked at the meter that
was measuring the power at the plate holder, and it seemed to be awfully
low. I looked at the laser supply, and it was where it was supposed to be
and a quick glance of the table looked ok. At that point, I lifted up my
goggles to try and get a better view of things, and BLAM!, I got hit right in
my right eye with the full power of one leg of the beam path. What had
happened was that one of the mag holders had not grabbed, or I had not
twisted the lock enough, and that turning mirror had nudged out of the
beam path, and the raw beam before it went to the spacial filter hit me
square in the eye. It felt like I had about 100 of those big screw in
flashlamps go off at the same time, and I seem to remember being
disoriented enough that I kinda fell backwards and into the corner of
the room. Needless to say, I couldn't see a thing, and I started to pound
on the wall for the guys next door to come open the door for me, which
they did. I spent the next 3 days with a full bore "screamer" migraine,
for those of you that get migraines, you know what the screamers are
like. The Optho guy at the hospital confirmed the burn, and I just basically
laid in bed, pumped full of demerol for the eye/headache for about 3-4
days, and then for the rest of that year, I went through about 4 different
eyeglass prescriptions while the burn "healed", or settled down. It was
not a fun experience, and I still believe that had I not been wearing those
goggles, I would have not allowed myself to get into such a position as
to let a beam hit me square in the face..
Anyway, that's the story...
Just my $.02
Doug <<<<
Take Care
Adam
