When I was a child, in my grandfather's bookcase there was a copy of
“Science Advances” by JBS Haldane.
If you aren’t familiar with Haldane he’s well worth a Google.

The most memorable concept in that book for me, other than his “Come
the revolution” Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn’t thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane’s book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).


--

Graham.

%Profound_observation%

On 02/03/16 14:41, Graham. wrote:

When I was a child, in my grandfather's bookcase there was a copy of
€œScience Advances€� by JBS Haldane.
If you arent familiar with Haldane hes well worth a Google.

The most memorable concept in that book for me, other than his €œCome
the revolution€� Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadnt thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldanes book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).


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


--
"I am inclined to tell the truth and dislike people who lie consistently.
This makes me unfit for the company of people of a Left persuasion, and
all women"

On Wed, 2 Mar 2016 14:50:31 +0000, The Natural Philosopher
wrote:

On 02/03/16 14:41, Graham. wrote:

When I was a child, in my grandfather's bookcase there was a copy of
“Science Advances” by JBS Haldane.
If you aren’t familiar with Haldane he’s well worth a Google.

The most memorable concept in that book for me, other than his “Come
the revolution” Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn’t thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane’s book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).


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

Cross polerised filters render white light as purple (violet?)
then there is road camber and vehicle roll to make the effect
imperfect.

--

Graham.

%Profound_observation%

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?

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?


--

Graham.

%Profound_observation%

"Graham." wrote in message
...

When I was a child, in my grandfather's bookcase there was a copy of
"Science Advances" by JBS Haldane.
If you aren't familiar with Haldane he's well worth a Google.

The most memorable concept in that book for me, other than his "Come
the revolution" Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn't thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane's book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

I imagine one of the problems is that the polariser on the windscreen will
cut out quite a lot of light, so it will be harder to see reflections off
distant objects - so you need even brighter headlights to compensate. All
other (unpolarised) lights would need to be brighter as well to compensate
for losses in the polarising filter on the windscreen.

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).

Actually this would not necessarily be a good idea. Sometimes it is better
to have constant illumination of the road ahead from lots of lights dotted
along the road, rather than rely on lights projecting forwards from you car,
which illuminate by inverse square law: objects close too will be very
bright and objects further away will be less bright. Providing that glare
from overhead lights as you pass each one isn't a problem, I prefer constant
illumination to light which is less good on distant objects.

The Natural Philosopher wrote:
On 02/03/16 14:41, Graham. wrote:

When I was a child, in my grandfather's bookcase there was a copy of
“Science Advances” by JBS Haldane.
If you aren’t familiar with Haldane he’s well worth a Google.

The most memorable concept in that book for me, other than his “Come
the revolution” Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn’t thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane’s book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).


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


No, there is always some leakage. It was being worked on in 1958 by some
colleagues.

On 02/03/2016 14:55, Graham. wrote:

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

Cross polerised filters render white light as purple (violet?)
then there is road camber and vehicle roll to make the effect
imperfect.


Not to mention side lights that are unpolarised.

On 02/03/2016 15:01, Martin Bonner wrote:

- 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?


Yes, but this was thought about soooo long ago, when there were far
fewer vehicles on the road. We shouldn't put off really good ideas
indefinitely.

On 02/03/2016 15:30, NY wrote:

Actually this would not necessarily be a good idea. Sometimes it is
better to have constant illumination of the road ahead from lots of
lights dotted along the road, rather than rely on lights projecting
forwards from you car, which illuminate by inverse square law:

Does inverse square apply to a directed beam of light? You could have
multiple light sources on the car, each highly directional.

"GB" wrote in message
...
On 02/03/2016 15:30, NY wrote:

Actually this would not necessarily be a good idea. Sometimes it is
better to have constant illumination of the road ahead from lots of
lights dotted along the road, rather than rely on lights projecting
forwards from you car, which illuminate by inverse square law:

Does inverse square apply to a directed beam of light? You could have
multiple light sources on the car, each highly directional.


Hmmm. You *may* have a point there. My knowledge of optics isn't good enough
to know.

On 02/03/2016 14:41, Graham. wrote:

When I was a child, in my grandfather's bookcase there was a copy of
“Science Advances” by JBS Haldane.
If you aren’t familiar with Haldane he’s well worth a Google.

The most memorable concept in that book for me, other than his “Come
the revolution” Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn’t thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane’s book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).



There are other road users than cars, some don't have windscreens to
polarize.

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.

"dennis@home" wrote in message
web.com...
There are other road users than cars, some don't have windscreens to
polarize.

Polaroid visors on crash helmets? :-) Polaroid sunglasses for other road
users such as pedestrians and cyclists? :-)


Do circular and linear polarising filters reduce the light intensity by
about the same amount, or is one better than the other?

I am still awaiting a prescription windscreen so that I don't need to wear
glasses.

Graham. wrote:

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

Reflections (from shiny cars, puddles etc) rotating the polarisation and
causing dazzle?

In message , GB
writes
On 02/03/2016 15:01, Martin Bonner wrote:

- 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?


Yes, but this was thought about soooo long ago, when there were far
fewer vehicles on the road. We shouldn't put off really good ideas
indefinitely.

Umm.. I have read bits of Haldane and concur on the politics.

If you removed 50% of the light energy from a filament source, aren't
you also going to gather 50% as heat at the filter?

--
Tim Lamb

dennis@home wrote:
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.

I thought it was nearer 70%, however it's some years since I
looked into this. One state in the US won't allow tinted front
windscreens at all if IRC. There is also the tilt factor of the
windscreen relative to the source which also comes into this. I had a
bad experience with a coated winscreen before Xmas where the in car
wireless RFID toll tag would only work on the LHS of the mirror, even
though the coating was supposedly not present all over. It was a pig to
remove the tag, even with a hair dryer and even then only 70% of the
glue transferred.

On 02/03/2016 14:41, Graham. wrote:

When I was a child, in my grandfather's bookcase there was a copy of
“Science Advances” by JBS Haldane.
If you aren’t familiar with Haldane he’s well worth a Google.

The most memorable concept in that book for me, other than his “Come
the revolution” Marxist style,

Good for him :-)

Although he did seem to have a very strange view about what went on in
the USSR . . .


--
Cheers, Rob

On 02/03/16 18:02, Tim Lamb wrote:
In message , GB
writes
On 02/03/2016 15:01, Martin Bonner wrote:

- 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?


Yes, but this was thought about soooo long ago, when there were far
fewer vehicles on the road. We shouldn't put off really good ideas
indefinitely.

Umm.. I have read bits of Haldane and concur on the politics.

If you removed 50% of the light energy from a filament source, aren't
you also going to gather 50% as heat at the filter?


Yes, but the visible light power is a small fraction of the total input
power in an incandescent bulk (about 1% for a torch bulb, should be a
bit better for halogen).

In message , Tim Watts
writes
On 02/03/16 18:02, Tim Lamb wrote:
In message , GB
writes
On 02/03/2016 15:01, Martin Bonner wrote:

- 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?


Yes, but this was thought about soooo long ago, when there were far
fewer vehicles on the road. We shouldn't put off really good ideas
indefinitely.

Umm.. I have read bits of Haldane and concur on the politics.

If you removed 50% of the light energy from a filament source, aren't
you also going to gather 50% as heat at the filter?


Yes, but the visible light power is a small fraction of the total input
power in an incandescent bulk (about 1% for a torch bulb, should be a
bit better for halogen).

Ah. OK

My back up thought is.. how much light would actually get through a
polarizing filter from an incandescent source?

--
Tim Lamb

Well there was the fringing interference pattern issues that this sort of
thing caused, and of course you are not always sure the null point is going
to coincide with the oncoming traffics setting if there is a camber on the
road etc.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Graham." wrote in message
...

When I was a child, in my grandfather's bookcase there was a copy of
"Science Advances" by JBS Haldane.
If you aren't familiar with Haldane he's well worth a Google.

The most memorable concept in that book for me, other than his "Come
the revolution" Marxist style, was a few paragraphs on polarized
headlamps.

The idea had been proposed by the inventor of Polaroid sheet
polarizers , Edwin Land.

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

I know it is said that it takes a genius to think of an idea that
later seems obvious, but in this case I really feel that if Land
hadn't thought of it, I would have, and I expect many here would say
the same.

Here's an good article on the subject

http://www.polarization.com/land/land.html

and here is the Haldane's book see page 183
http://www.archive.org/stream/scienc...ge/n7/mode/2up

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

Hell, they can then even turn all the street-lighting off!
(As they seem to be doing so anyway).


--

Graham.

%Profound_observation%