More Consequences for Laser pranksters

On 2014.05.13, 15:07 , Savageduck wrote:

http://blog.sfgate.com/crime/2014/05...t-helicopters/

Good.

A kid (18 ish) at a party lased me pretty close last year - I was not happy.


--
"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

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 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.

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


--
"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

On 2014.05.13, 23:39 , nospam wrote:
In article 2014051319421166972-savageduck1@REMOVESPAMmecom,
Savageduck 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.

actually it's much narrower than that.

typical beam width is 3 feet at 1000 feet distance, which is a typical
clocking distance for vehicles, if not a bit far.

3' is definitely wider than a point focused beam, but it doesn't mean
it's entirely harmless. it's long term effects are not known. they're
approved as class 1 devices, but they also come with warnings.

it sends pulsed infrared light, whose *average* power is what is used
to determine eye safety, not instantaneous power.

The diffusion, if only 1 m at 300m reduces the power by many orders of
magnitude v. a point.

As usual you brought up a non-point to make ... no point at all.

--
"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 , Alan Browne
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.

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 wore
protective glasses - and it was not visible wavelengths).

yep.

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

the windshield reflects very little and lidar can be used through glass
although it usually is not.

the risk is low because the average power is low due to the pulsing,
not the diffusing. it has a very, very low duty cycle.

In article , Alan Browne
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.

actually it's much narrower than that.

typical beam width is 3 feet at 1000 feet distance, which is a typical
clocking distance for vehicles, if not a bit far.

3' is definitely wider than a point focused beam, but it doesn't mean
it's entirely harmless. it's long term effects are not known. they're
approved as class 1 devices, but they also come with warnings.

it sends pulsed infrared light, whose *average* power is what is used
to determine eye safety, not instantaneous power.

The diffusion, if only 1 m at 300m reduces the power by many orders of
magnitude v. a point.

As usual you brought up a non-point to make ... no point at all.

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?

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 at ca
rs.

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.

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 wore
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 the
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 not
be an issue with the windshield and any eyeballs behind it.

--
Regards,

Savageduck

On 2014.05.14, 16:24 , nospam wrote:
In article , Alan Browne
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.

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 wore
protective glasses - and it was not visible wavelengths).

yep.

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

the windshield reflects very little and lidar can be used through glass
although it usually is not.

It would reflect a good chunk. No figures here, but lasers oblique to
glass (most windshields are at an angle) do reflect quite a bit of their
energy.

the risk is low because the average power is low due to the pulsing,
not the diffusing. it has a very, very low duty cycle.

A combination to be sure. But the comparison in this discussion is with
a laser pointer without a diffuser or scintillator.

As an example, if the laser made a 1mm diameter circle without a
diffuser and then that is spread to 1m diameter at 300 metres with a
diffuser, then the surface power would be 1,000,000 times lower where
the laser hit someone's eye.

OTOH, a typical pulse rate is 1 kHz with a duty cycle of 30 ns. Doesn't
sound like much - OTOH, that's 30X more power than what is delivered due
to diffusion.

To say the diffusion is not significant is plain silly.

--
"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

On 2014.05.14, 16:24 , nospam wrote:
In article , Alan Browne
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.

actually it's much narrower than that.

typical beam width is 3 feet at 1000 feet distance, which is a typical
clocking distance for vehicles, if not a bit far.

3' is definitely wider than a point focused beam, but it doesn't mean
it's entirely harmless. it's long term effects are not known. they're
approved as class 1 devices, but they also come with warnings.

it sends pulsed infrared light, whose *average* power is what is used
to determine eye safety, not instantaneous power.

The diffusion, if only 1 m at 300m reduces the power by many orders of
magnitude v. a point.

As usual you brought up a non-point to make ... no point at all.

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?

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.

--
"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

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 at ca
rs.

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.

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 wore
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 the
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 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.


--
"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

On 2014-05-14 20:24:06 +0000, nospam said:

In article , Alan Browne
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.

actually it's much narrower than that.

typical beam width is 3 feet at 1000 feet distance, which is a typical
clocking distance for vehicles, if not a bit far.

3' is definitely wider than a point focused beam, but it doesn't mean
it's entirely harmless. it's long term effects are not known. they're
approved as class 1 devices, but they also come with warnings.

it sends pulsed infrared light, whose *average* power is what is used
to determine eye safety, not instantaneous power.

The diffusion, if only 1 m at 300m reduces the power by many orders of
magnitude v. a point.

As usual you brought up a non-point to make ... no point at all.

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.

--
Regards,

Savageduck