In article , Alan Browne
wrote:

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.

not that much. most goes through it.

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.

except that the power of a lidar gun transmitter is significantly
higher than a pocket laser pointer.

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.

it's not the only part.