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.

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.

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).

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

Really - get your facts straight.

--
"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