I'm going to "Laser" a pilot.

If anyone else can think of anything else they'd like to see tried (no,
not in *my* plane) please post it here.

This isn't meant to be a scientific experiment or to become information
used instead of any government research or guidelines. OK?

moo

How about:
1. Acquire a standard optometrist eye chart.
[A television resolution chart would be a good substitute]
2. Before each exposure, determine visual acuity.
3. After each exposure, repeat acuity test
4. Start at a lower exposure duration and work up.
[This may require performing the test(s) on separate nights]
5. Do the whole thing during the day, facing away from the sun.
6. Chart your work

Hmmm, before step 1, check your medical insurance and have an
optometrist or opthomalogist do a retinal scan, before and after.

"Casey Wilson" N2310D @ gmail.com wrote in

1. Acquire a standard optometrist eye chart.
[A television resolution chart would be a good substitute]
2. Before each exposure, determine visual acuity.
3. After each exposure, repeat acuity test
4. Start at a lower exposure duration and work up.
[This may require performing the test(s) on separate nights]
5. Do the whole thing during the day, facing away from the sun.
6. Chart your work

Hmmm, before step 1, check your medical insurance and have an
optometrist or opthomalogist do a retinal scan, before and after.


Apart from the retinal scan, pointless. The claim is that tiny lasers can
blind pilots. It's bull****. There isn't even a valid theory behind it.
My work is just entertainment.

moo

Happy Dog wrote:

"Casey Wilson" N2310D @ gmail.com wrote in

Apart from the retinal scan, pointless. The claim is that tiny lasers can
blind pilots. It's bull****. There isn't even a valid theory behind it.
My work is just entertainment.

moo

Although I agree that it is impossible to hold a laser on a sufficiently
small area at the distances described (a 1 degree fluctuation causing a ca.
90 ft. movement at 1 mile if my math is correct), there is valid theory
behind it. Maximum permissible exposure when looking into a laser beam is a
function of exposure time.

For wavelengths of 400 nm to 1.4 um: [1]

t = 1 ns to 2x10^-5 s MPE = 0.0005 mJ cm^-2
t = 2x10^-5 s to 10 s MPE = 1.8xt^(3/4) mJ cm^-2
t 10 s MPE = 10 mJ cm^-2

Laser device in question has a rated power of 5 mW.
1 W = 1 J/s
5 mW = 5 mJ/s

Assuming under the worst case the beam spread results in a beam no bigger
than 1 square centimeter (and there are 2.54 centimeters in an inch), the
exposure NEVER exceeds the MPE, even for very long exposure times. In
reality the beam spread is much greater. A device I tested has a beam
spread of over 2 inches at 50 feet.

How accurately must one be to hold the 1 cm beam on target at the target
distance? Assuming a distance of 1 km, a 1 cm movement is equivalent to an
angular displacement of:

tan a = 1 cm / 1 km = 1 x 10^-2 / 1 x 10^3 = 1 x 10^-5
a =~ .00001 radians =~ 20 arc seconds

So, the whole thing doesn't wash. The power is insufficient, the beam spread
is too great, and the required pointing accuracy is too high.

[1] Jurgen R. Meyer-Arendt, M.D., "Introduction to Classical and Modern
Optics", 2nd ed.

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.

"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.

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. 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. 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.

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.