On 02/03/2016 15:24, Graham. wrote:
On Wed, 2 Mar 2016 07:01:15 -0800 (PST), Martin Bonner
wrote:

On Wednesday, 2 March 2016 15:50:34 UTC+1, The Natural Philosopher wrote:
On 02/03/16 14:41, Graham. wrote:

Basically the idea is we all drive about using un-dipped headlights
with the lights, and windscreens polarized with a 90deg differential.

So this issue must have been considered time and time again, yet
always rejected for mainstream use. Why?

Oh dear. Does this mean you wouldn't see cars headlights coming straight
at you?

No. Polarizers are not 100% efficient, so you would still see a bright
spot - but *most* of it would be blocked, so you wouldn't be blinded
either.

Two problems though:
- Polarizers cut out about half the light.
- That means the headlamps are only half as bright.
- It also means that the windscreen cuts out about half the reflected
light.
- Net result: Your beam headlight needs to be 4x as bright!
(Actually, LEDs might be able to emit polarized light directly, rather
than blocking light of the wrong polarization. Still have x2.)

- The killer problem though is legacy. If I am driving towards you with
my new car with polarized headlamps, how do I know I don't need to dip
my headlamps?

How much ND filtering is involved in a typical pimpmobile windscreen?



If its legal, not much.
They have to transmit 96% IIRC.