Unauthorized Laser Illumination Event

"WingFlaps" wrote in message
oups.com...
On Nov 13, 3:42 pm, Mxsmanic wrote:
The beam
of a good quality laser (highly collimated, that is) will hardly spread
out at
all over a distance of a few thousand feet and thus may still be only a
millimetre or two in diameter.

Complete ********. Just buy a laser pointer and measure the spot size
after 50'. It's already cm wide. The cavity of laser diode is just
too short to produce such high degree of collimation...

Garden-variety laser pointers aren't the same as the newer high-powered
green lasers, though, are they? (For example:
http://www.greenlaserbeam.com/ )

-c
not a physicist.

On Tue, 13 Nov 2007 10:01:03 -0500, "Marco Leon"
wrote:

I reacted this way because it irked me that this was not an accidental
event. I'd be kicking myself for days if I did nothing. I'm glad you would
reconsider. If the guy actually got caught, just think of how satisfying it
would be.

Guys...

I swapped private emails with Marco, 'cause I'm VERY familiar with the
area where it happened. As in the "riding my bicycle" familiar.

The area is an extremely noise sensitive area of mostly antique and
locally historic homes. Marco was told by the tower to turn left
after going missed. The published missed goes right. HFD has signs
on the runway entrances advising pilots how to avoid this area. The
area is marked as "noise sensitive" on NACO plates.

Read into that what you'd like.

B A R R Y writes:

The area is an extremely noise sensitive area of mostly antique and
locally historic homes. Marco was told by the tower to turn left
after going missed. The published missed goes right. HFD has signs
on the runway entrances advising pilots how to avoid this area. The
area is marked as "noise sensitive" on NACO plates.

Read into that what you'd like.

The implication is that some people in the area are selfish enough to think
that blindness and/or death are appropriate punishments for anyone who dares
to disturb their desire for silence.

Orval Fairbairn writes:

It seems that they would have to have at least a telescopic sight on the
laser and have that mounted on a rifle stock, so they could get a
precision aiming.

It would have to be precise to within an inch or so, or the beam would have to
be relatively intense and spread slightly to make a larger target at a
distance. A good-quality laser beam doesn't diverge very quickly, which makes
it hard to hit a small target but greatly increases the damage if you succeed.

WingFlaps writes:

Eye damage would be so unlikely at 1000' from a laser pointer that I
doubt the veracity of this tale.

Hand-held laser pointers are not the problem. More powerful lasers are used
that can easily damage the eye. And the power of a laser doesn't diminish
taht much with distance, since the beam is tightly collimated.

WingFlaps writes:

Complete ********. Just buy a laser pointer and measure the spot size
after 50'. It's already cm wide.

Laser pointers are hardly the state of the art.

Gatt writes:

Garden-variety laser pointers aren't the same as the newer high-powered
green lasers, though, are they? (For example:
http://www.greenlaserbeam.com/ )

No, they are not. They are still not the most collimated beams around, but
they are collimated enough to cover just about the area of a person's face at
a few thousand feet.

The total energy delivered to the eye in this case would be in the range of
microwatts at several thousand feet, and it would be virtually impossible to
accurately aim a handheld pointer at this range. So it would be more of a
nuisance to vision than a damage hazard.

Unfortunately, there are still more powerful lasers available. Most people
dramatically underestimate the hazards of laser light. I'd be nervous about
those green pointers just out of concern for my own vision. All you have to
do is accidentally aim it at a reflective surface, and next thing you know you
have a retinal burn.

WingFlaps writes:

C'mon let's have a reality check. Can you identify a single case of
actual vision damage at significant range from a laser pointer?

Yes. The FAA has documented them, and the Civil Aerospace Medical Institute
has been collecting documentation on laser illumination events and eye
injuries for over a decade.

Even if all the light were collected by the eye and the eye were focused to
maximise energy delivery on the retina the energy of a laser pointer
is just too low to cause damage before the blink reflex protects the
eye.

Not true. That would produce immediate eye damage. Ninety-five milliwatts
concentrated by a factor of 100,000 by an eye lens focused on infinity will
practically punch a hole through the retina even at very short exposures.
Even five milliwatts is dangerous.

That's why they can be sold in stores... think about it!

I have. And it's a serious problem. If you think it's harmless, just look
down the beam of a few such lasers yourself and see how your vision works
after a while. If you're right, no problem. If you're wrong, well, I guess
you won't be reading USENET any more.

"B A R R Y" wrote

I swapped private emails with Marco, 'cause I'm VERY familiar with the
area where it happened. As in the "riding my bicycle" familiar.

The area is an extremely noise sensitive area of mostly antique and
locally historic homes. Marco was told by the tower to turn left
after going missed. The published missed goes right. HFD has signs
on the runway entrances advising pilots how to avoid this area. The
area is marked as "noise sensitive" on NACO plates.

Read into that what you'd like.

I read into it, and I don't like what I read.

Basically, if you fly over rich guy's pretty house, and make noise, he feels it
is his right to try and blind you with a laser.

Kinda' goes past the reaches of decency, doesn't it? :-(
--
Jim in NC

"WingFlaps" wrote C'mon let's have a reality check. Can
you identify a single case of
actual vision damage at significant range from a laser pointer? Even
if all the light were collected by the eye and the eye were focused to
maximise energy delivery on the retina the energy of a laser pointer
is just too low to cause damage before the blink reflex protects the
eye. That's why they can be sold in stores... think about it!

These are not the less than 5 mW pointers that your are accustomed to.

I have seen 295 mW lasers for sale on the web. That would be 59 times more
power ! ! !

Those are expensive but available.

A 50mW laser for sale for $150. That would make it 10 times as powerful. If a
red 5W laser can leave a dot in you vision, a 50 could definitely leave a
lasting effect.

The FAA and FBI have several cases on file, with vision damage. It is a real,
not imagined, problem.
--
Jim in NC