I'm going to "Laser" a pilot.

"Larry Dighera" wrote in message
Laser device in question has a rated power of 5 mW.

Actually, some are available with over 10 times that power:
http://www.wickedlasers.com/products.php

However, as you assert, they are probably still incapable of
inflicting retinal damage at the distances involved when aimed at an
aircraft in flight.

As I've said before, I have small NdYAG lasers that produce 3 watts (600x)
and Gas Ion ones that produce over twenty watts. But that's not what the
hype is about.

moo

On Fri, 28 Jan 2005 18:44:25 -0500, "Happy Dog"
wrote in
: :

"Larry Dighera" wrote in message
Laser device in question has a rated power of 5 mW.

Actually, some are available with over 10 times that power:
http://www.wickedlasers.com/products.php

However, as you assert, they are probably still incapable of
inflicting retinal damage at the distances involved when aimed at an
aircraft in flight.

As I've said before, I have small NdYAG lasers that produce 3 watts (600x)
and Gas Ion ones that produce over twenty watts.

But those are not small handheld laser pointers, right?

But that's not what the hype is about.

Right. So why mention them?

The US government possesses far larger lasers than you ever will, but
that too is not germane to the discussion, unlike those in the link I
provided.

"Larry Dighera" wrote in message
...
On Fri, 28 Jan 2005 18:44:25 -0500, "Happy Dog"
wrote in
: :

"Larry Dighera" wrote in message
Laser device in question has a rated power of 5 mW.

Actually, some are available with over 10 times that power:
http://www.wickedlasers.com/products.php

However, as you assert, they are probably still incapable of
inflicting retinal damage at the distances involved when aimed at an
aircraft in flight.

As I've said before, I have small NdYAG lasers that produce 3 watts (600x)
and Gas Ion ones that produce over twenty watts.

But those are not small handheld laser pointers, right?

But that's not what the hype is about.

Right. So why mention them?

The US government possesses far larger lasers than you ever will, but
that too is not germane to the discussion, unlike those in the link I
provided.

On Fri, 28 Jan 2005 23:35:34 +0000, 10Squared
wrote in ::

Larry Dighera wrote:

On Fri, 28 Jan 2005 11:53:03 +0000, 10Squared
wrote in ::

Laser device in question has a rated power of 5 mW.

Actually, some are available with over 10 times that power:
http://www.wickedlasers.com/products.php

However, as you assert, they are probably still incapable of
inflicting retinal damage at the distances involved when aimed at an
aircraft in flight.

OK, let's see what happens with their most wicked laser. I see the Extreme
Phoenix with a power rating of 500mW.

Just to be accurate, I believe the Wicked laser diode is RATED at
500mW, but the claimed output is 70 to 80 mW, IIRC.

The quoted beam divergence is 1.2 mrad. Assuming a distance of 1 km,

a = 1.2 mrad
tan a = x / 1 * 10^3
x = 10^3 * m * x tan a
tan a =~ a
x = 1.2 * 10^3 * 10^-3 * m = 1.2 meters

To be conservative, let's use the beam divergence of only .5 mrad, or .5
meters at 1 km:

.5 m = 50 cm
p = 500 mW / (3.141 * 25 * 25 * cm^2)

Your 500 mW laser has a power of about .25 mW/cm^2 at 1 km. Again, much less
than the MPE for constant exposure.

Intuitively, I didn't question that, but thank you for the formulae.

That brings up another point: Who is going to stare at a laser? Brief
exposure is uncomfortable and will cause you to look away quickly, so
MPE equation #2 is probably the one that applies.

So you're saying that closing one's eyes or looking away is reflexive.
What length of time would you estimate it takes for that reflex to
occurr?

What magnitude of laser power would you estimate to be required to
cause retinal damage at say 1 mile for what period of time?

"Larry Dighera" wrote in message
...

Big Snip!!


What magnitude of laser power would you estimate to be required to
cause retinal damage at say 1 mile for what period of time?

If I may change to a different laser wavelength with a conforming
lens, a 1 megawatt laser will cause nearly instantaneous, and irreversible,
damage at ranges beyond one mile.
I agree with Happy Dog. The toys being bandied about here, and what
are available on the consumer market, are virtually harmless. On the other
hand, a NdYAG for example, is NOT in the visible spectrum and you wouldn't
know to look away until that blurry spot appeared in your visual field. Same
with CO2 and a host of other weapons grade gadgets.
My work with lasers, admitedly years, decades ago, made me
hyper-concious of the dangers. Especially having to sit through a
comprehensive retinal scan and image record every three months, just to make
sure I hadn't screwed up. Which in my lab was very difficult -- it two
people with separate keys on opposite sides of the room and a 3-second
klaxon to turn the gadgets on. I don't even like to see laser pointers used
in darkened rooms, even though I would testify to their safety.

In article ,
Larry Dighera wrote:


What magnitude of laser power would you estimate to be required to
cause retinal damage at say 1 mile for what period of time?

The problem is not damage, it's "dazzle" -- having what seems to be a
_very_ bright light more or less in the center of your field of view and
coming straight into your eyes.

Yes, you blink, or look away -- but after you open your eyes the bright
incoming light may still be there, very close in angle or position to
the terrain or the instruments you have to look at, so you can't really
easily block it. Even with the laser positioned somewhat off to the
side there may be a lot of bright scatter from dirt or scratches on the
windshield, very similar to the situation of driving a car with a dirty
or scratched windshield (or just with aging eyeballs) looking into the
bright headlights of oncoming cars. And, any night vision adaptation
you may have had is gone (night vision can be wiped out considerably
faster than it can be restored).

All of these effects can be produced at light intensities way, way below
the level that produces any permanent damage to the retina. Though I'm
no expert on this subject, I have also been told that sustained exposure
to this kind of illumination in a situation where you can't just "turn
it off" and where the light levels, although below permanent damage, are
well above what leads to you to blink, and especially if they occur in
stressful situations with demanding performance requirements, can
rapidly lead to various kinds of psychological distress.

"10Squared" wrote in message

OK, let's see what happens with their most wicked laser. I see the Extreme
Phoenix with a power rating of 500mW.

Their most powerful one is rated at less than 100mw. They claim to use a
500mw diode but the actual output is around 90mw max.

Your 500 mW laser has a power of about .25 mW/cm^2 at 1 km.

Make that .05mw.

moo

"Casey Wilson" N2310D @ gmail.com wrote in

If I may change to a different laser wavelength with a conforming
lens, a 1 megawatt laser will cause nearly instantaneous, and
irreversible, damage at ranges beyond one mile.
I agree with Happy Dog. The toys being bandied about here, and what
are available on the consumer market, are virtually harmless. On the other
hand, a NdYAG for example, is NOT in the visible spectrum and you wouldn't
know to look away until that blurry spot appeared in your visual field.
Same with CO2 and a host of other weapons grade gadgets.

NdYAGs are available in visible wavelengths. As for UV or IR lasers, how
would you aim them?

moo

"AES" wrote in message

Yes, you blink, or look away -- but after you open your eyes the bright
incoming light may still be there, very close in angle or position to
the terrain or the instruments you have to look at, so you can't really
easily block it.

Missed approach. Problem solved.

All of these effects can be produced at light intensities way, way below
the level that produces any permanent damage to the retina. Though I'm
no expert on this subject, I have also been told that sustained exposure
to this kind of illumination in a situation where you can't just "turn
it off" and where the light levels, although below permanent damage, are
well above what leads to you to blink, and especially if they occur in
stressful situations with demanding performance requirements, can
rapidly lead to various kinds of psychological distress.

Did an "expert" tell you this?

moo

On Sat, 29 Jan 2005 03:56:23 GMT, "Casey Wilson" N2310D @ gmail.com
wrote in HPDKd.2876$RI.2060@trnddc06::


"Larry Dighera" wrote in message
.. .

Big Snip!!


What magnitude of laser power would you estimate to be required to
cause retinal damage at say 1 mile for what period of time?

If I may change to a different laser wavelength with a conforming
lens, a 1 megawatt laser will cause nearly instantaneous, and irreversible,
damage at ranges beyond one mile.

So you figure that 1-megawatt is the MINIMUM power necessary? Given
the fact that the majority of homes in the US are served by a
24-kilowatt (2.4% of a megawatt) electrical service, it's not likely
that any retinal damage is possible without browing out half a
neighborhood. :-)