Monday, 5 January 2015

Polaroid Eliminates Headlamp Dazzle

In 1929 Edwin H. Land patented plastic film that could polarise light.

If headlights are polarised \\\\\ and the windscreen or driver's glasses are polarised /////, then direct light is absorbed.


From polarization.com
"It was not the sunglasses, nor the camera filters, nor the 3-D movies, nor the adjustable-tint windows, nor the displays, nor the innumerable laboratory and industrial instruments that eventually used his sheet polarizer. The foremost application in his mind was to eliminate the glare danger of automobile headlights. Together with his team he solved all the technical problems. The invention had the potential of saving many lives. But his decades-long quest for the adoption of anti-glare headlights was unsuccessful."
Why was it not adopted ? No real reason !
"For such a system to work well, every car would have to use it. But then, what would be the advantage over the competition for a car company to introduce it? They only saw just more government regulations. They had more reasons to drag their feet than with seatbelts and airbags."
Consider the first car to use it - of course, the driver of that car will have a polaroid windscreen or glasses, but because no-one else has polarised headlamps, he will still be dazzled. Since no-one else has polaroid windscreen or glasses, they will still be dazzled by his polarised headlights.

It's like the first VideoPhone made by Plessey in the nineties - if you bought one, who would you be able to call ?

Of course the polariser absorbs half the light, and the glasses absorb half of the scattered light you want to see. So brightness is reduced by at least a factor of four.

Now headlights are so bright that people are petitioning governments to ban the brightest.
Edwin Land's invention is an idea whose time has come !

Why is it not being adopted ?

See also

"StVZO, a German traffic standard. This requires that the luminous intensity of cycle lamps should be no more than 200 cd at 3.5 degrees above the beam centre. The ECE regulation governing motorcycle headlamps is ECE R113. This decrees that the luminous intensity should be no more than 625 cd."
"ECE R112 for headlamps (which I believe is used in the UK) calls out a 350 candela maximum at the B50L point which is the oncoming driver glare point. This means that approximately 700 candela could legally be coming from the car (2 headlamps). In fact the regulation requires vehicles to have a minimum of 125 candela at the horizon from each lamp (or 250 combined candela)"
  1. Where were the lights pointed ?
  2. Did they measure car and motorbike lights for comparison ?
  3. I'm pretty sure they're comparing full-beam bike-lights to dipped-beam car-lights ?