More Consequences for Laser pranksters

On 2014-05-14 21:46:03 +0000, RichA said:

On Tuesday, May 13, 2014 10:42:11 PM UTC-4, Savageduck wrote:
On 2014-05-14 02:27:52 +0000, nospam said:



In article , PeterN

wrote:

Although I'm sure it happens, one never hears of idiots who shine
lasers at cars.

cops do it every single day.



They use laser guns which produce a very diffused beam with a target
circle of about 60'', not a high power point focused laser beam.
Also the law enforcement laser guns I am aware of do not use a light
which is in the visible spectrum and is not likely to cause any retinal
injury.

Anyone who uses a green laser on a gun is an idiot, it just tells
whoever is or might be shooting at you where you are because the beam
of a powerful green laser is easily visible at night whereas a red one
isn't.

Your ignorance is showing. We are talking about laser / Lidar guns use
by traffic police to get an accurate speed reading on vehicles, not
firearms.
Laser weapons sights are a different animal altogether


--
Regards,

Savageduck

On 2014-05-14 21:55:06 +0000, Alan Browne
said:

On 2014.05.14, 17:17 , Savageduck wrote:
On 2014-05-14 21:03:30 +0000, Alan Browne
said:

On 2014.05.14, 16:48 , Savageduck wrote:
On 2014-05-14 20:10:39 +0000, Alan Browne
said:

On 2014.05.13, 22:42 , Savageduck wrote:
On 2014-05-14 02:27:52 +0000, nospam said:

In article , PeterN
wrote:

Although
I'm sure it happens, one never hears of idiots who shine lasers a
t
ca
rs.

cops do it every single day.

They use laser guns which produce a very diffused beam with a targe
t
circle of about 60'', not a high power point focused laser beam.
Also the law enforcement laser guns I am aware of do not use a ligh
t
which is in the visible spectrum and is not likely to cause any ret
in
al

injury.

Invisible lasers can cause a lot of damage too if not diffused. In
our laser lab where I used to work (I was not part of that lab but
occasionally worked with those engineers on some projects), they wor
e
protective glasses - and it was not visible wavelengths).

Per the Wikipedia article the police laser cone is about 1 m at 300
metres distance. Still enough diffusion to prevent eye damage. And

of course the glass on the car would reflect a lot of it away from t
he

driver's eyes as well as absorb some of the energy.

Primary target is the front of the vehicle, usually the number plate,

the diffused energy cone would cover the entire width and typically n
ot

be an issue with the windshield and any eyeballs behind it.

Surely - but there's also the issue of missing the target and hitting
innocent bystander eyeballs.

Where would this hypothetical innocent bystander be? Standing on the
shoulder of the highway? Perhaps moving faster than the traffic flow, o
n
foot?

Missing the target is very unusual, given the transitory nature of
target acquisition and the diffused beam at typical ranges. It is sort
of like shooting a tennis ball at 20 feet with a shotgun.

It's all moot (given the actual facts), but anyone could be firing the
laser at anyone anywhere. The combinations of:

- very low power (50 micro-watts)
- pulse rate/duty cycle
- diffusion
- reflection off of windshields and some absorption
- very short "event" cycle (1/4 of a second or so).

Make the power on eyes issue completely moot - so you have to wonder why
nofacts brought it up in the context of a much more powerful CW laser...

He is the universal expert. I am sure you knew that.

--
Regards,

Savageduck

On 2014-05-14 21:55:32 +0000, nospam said:

In article , Alan Browne
wrote:

have you even used a lidar gun?

My experience is in pulsed, CW and FM/CW radar where I worked mainly in
embedded s/w and test s/w for those systems. We also (the
aforementioned lab) built a pulsed laser for obstacle detection (proof
of concept) which I've used in demos (in Japan). That never entered a
product development period, alas. Eventually our radar work would be in
competition with a German co. who used lasers (and reasonably well at
terrifically high cost and weight) for that purpose. And yes, with some
of the radars we made, safety was indeed an issue (the computation
always accounted for pulse rate, duty cycle, area of exposure, power
(and at least with scanning devices) scan rates.

You could say I'm quite familiar with both.

that helps, but if you actually used a lidar gun to clock cars you will
see that the windshield is not as reflective as you claim.

....and with which law enforcement agency did you gain that experience?

--
Regards,

Savageduck

On 2014-05-14 21:55:33 +0000, nospam said:

In article 2014051414174666962-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

Primary target is the front of the vehicle, usually the number plate,
the diffused energy cone would cover the entire width and typically not
be an issue with the windshield and any eyeballs behind it.

Surely - but there's also the issue of missing the target and hitting
innocent bystander eyeballs.

Where would this hypothetical innocent bystander be? Standing on the
shoulder of the highway? Perhaps moving faster than the traffic flow,
on foot?

the driver of the vehicle for one, as well as passengers.

Missing the target is very unusual, given the transitory nature of
target acquisition and the diffused beam at typical ranges. It is sort
of like shooting a tennis ball at 20 feet with a shotgun.

the beam hitting places other than the license plate or headlights is
quite common. that's what lidar detectors pick up (as well as scatter).

Duh!

--
Regards,

Savageduck

On 2014-05-14 21:55:34 +0000, nospam said:

In article 2014051414051812228-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

it does reduce the power but that's not what makes it considered to be
safe. it's the low duty cycle which means it's average power is low.
the actual pulses are quite strong.

have you even used a lidar gun?

Have you?
I have.

sure have, as well as many radar guns.

cops aren't the only ones who use them, and they don't generally know
what goes on inside at a technical level either.

....er right.

--
Regards,

Savageduck

On 2014.05.14, 17:55 , nospam wrote:
In article , Alan Browne
wrote:


By the way, what really makes the police LIDAR's eyesafe is the very low
laser power. Power levels at the laser aperture are on the order of 50
micro-Watts.

the average power is low because of the duty cycle.

Fair enough - the avg. power is very, very low.

And spread out by a factor of 1/1000000 at 300 m distance.

And meanwhile we wonder: Why did you even bring this up when the
subject is eye safety for pilots facing CW green lasers?


the actual power of the pulse is 1,000,000 times higher, at about 50
*watts*.

kustom prolaser:
https://www.google.com/patents/US5221956
The gallium-arsenide laser produces laser energy having a wave length
of 905 nanometers with a peak power output of approximately 50 watts
and a 30 to 50 nanosecond pulse width.
laser atlanta:
https://www.google.com/patents/US6108071
In a preferred embodiment, the emitter is a GaAs type, producing
laser radiation having a wavelength of about 905 nanometers, with a
peak power output of approximately 50 watts and a 30-50 nanosecond
pulse width.

On green pointers they are 10 - 100 mW. On red lasers (still eye safe
ish) they are about 1 to 5 mW (often sold at higher than that, however).

the difference is that laser pointers are a continuous beam, not pulsed.

Another 200 - 2000 X less power for the police devices v. the device in
question.

other way around. lidar guns have substantially higher power laser
diodes.

Really - get your facts straight.

they are correct.

Meaningless and incomplete, actually. Since the spreading of the beam
contributes 30X more power drop (at 300m) and of course had nothing to
do with the issue of pilots being hit with green lasers.

--
"Big data can reduce anything to a single number,
but you shouldn’t be fooled by the appearance of exactitude."
-Gary Marcus and Ernest Davis, NYT, 2014.04.07

In article 2014051415414273585-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

that helps, but if you actually used a lidar gun to clock cars you will
see that the windshield is not as reflective as you claim.

...and with which law enforcement agency did you gain that experience?

law enforcement agencies are not the only place to learn how to use a
radar or lidar gun or where one can be obtained.

On 2014-05-14 23:00:41 +0000, nospam said:

In article 2014051415414273585-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

that helps, but if you actually used a lidar gun to clock cars you will
see that the windshield is not as reflective as you claim.

...and with which law enforcement agency did you gain that experience?

law enforcement agencies are not the only place to learn how to use a
radar or lidar gun or where one can be obtained.

What exactly were you clocking? Certainly not baseballs in a batting
cage or tennis serves, at least not with a Lidar gun.

--
Regards,

Savageduck

In article , Tony Cooper
wrote:

that helps, but if you actually used a lidar gun to clock cars you will
see that the windshield is not as reflective as you claim.

...and with which law enforcement agency did you gain that experience?

law enforcement agencies are not the only place to learn how to use a
radar or lidar gun or where one can be obtained.

What? They have them in coach class on airlines, now? Available for
market share surveys?

you are a blithering idiot.

In article 2014051416134359922-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

that helps, but if you actually used a lidar gun to clock cars you will
see that the windshield is not as reflective as you claim.

...and with which law enforcement agency did you gain that experience?

law enforcement agencies are not the only place to learn how to use a
radar or lidar gun or where one can be obtained.

What exactly were you clocking? Certainly not baseballs in a batting
cage or tennis serves, at least not with a Lidar gun.

for laser, mainly vehicles and bicycles but sometimes other things.
i've also used it for distance measurement.

for radar, pretty much anything that moves, although not everything has
a big enough radar cross section.