Saturday, June 09, 2007


Caught in the Headlights

I've got an article in this week's New Scientist about Polaroid founder Edwin Land's doomed crusade to mandate polarizing anti-glare headlights and windshields on cars:

As early as 1920, federal officials had declared the blinding glare of car headlights the country’s “chief road peril”... Would-be solutions proliferated. “Mr. Automobilist! Shade Your Headlights,” commanded one advert for Wridgway No-Glare Shade in 1909, while the Osgood Deflector Lens promised to “Light the Ground, Not the Air” and the Blindless Headlight Company pledged to “eliminate glare” altogether.... Nothing quite worked....

[But Land realized] A polarising filter "combs" incoming light so that only waves moving in one particular plane pass through. Two polarising filters held at angles to each other, so that the combing "teeth" form a crossbar, produce a striking effect: darkness. The trick, then, was to put a polarising filter over the headlight and a second filter over the windscreen, each oriented at the same 45 degree angle to the road.

So why don’t we have polarising headlights today? First, the US motor industry showed little interest in safety devices in the postwar years. “Automobile companies were not economically motivated, because they could sell all the cars they wanted,” Land later told interviewers. And polarisers were doubly damned: to work, they would have to be adopted by every car manufacturer. No company was willing to be the first...

Land spent decades on his anti-glare system -- it's why Polaroid was founded. ("Polaroid" itself is the name of the polarizing sheet that Land invented to apply to headlights and windshields.) The famed camera business was almost an accident, and came much later -- a profitable distraction from his original mission.

For those who don't subscribe, here's the article's shocker: a 2001 AAA study (pdf file) concluded that, six decades years later, Land is still right: "With one technological stroke, a quantum leap in highway safety could be accomplished... Polarized lighting is the only countermeasure for headlight glare which has the potential to be used in all situations and resolve all problems."

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