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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2007Status of polarizing headlamp filters
I was reading about this idea today. If all headlamps are fitted with a polarizing filter, then other drivers can almost completely eliminate glare by wearing glasses (or coating their windscreen) with another polarizing filter, perpendicular to the other. The article I read noted that one major problem was that the polarization process would block 50% of the light output of a conventional incandescent lamp, meaning they wouldn't do their job as well; and it speculated that when lighting technology improved in future to include lighting devices that could emit polarizing light, then this idea might have its day again. Is anyone producing such a thing commercially at the moment? > I was reading about this idea today. If all headlamps > are fitted with a polarizing filter, then other drivers can [quoted text clipped - 12 lines] > Is anyone producing such a thing commercially > at the moment? It would work great as long as you didn't drive at night. >I was reading about this idea today. If all headlamps > are fitted with a polarizing filter, then other drivers can > almost completely eliminate glare by wearing glasses > (or coating their windscreen) with another polarizing > filter, perpendicular to the other. You wouldn't eliminate the glare, you could completely eliminate the light altogether. Probably not a good idea. Two polarizing screens over the same light source, when they're in the proper phase, will block out all light. Try this with polarized sunglasses & an LCD watch (the display is polarized, otherwise it wouldn't work). Some car radios can't be seen with polarized sunglasses on for the same reason. Years ago my uncle (then a pilot in the US Air Force) told me that the aviator sunglasses they're issued aren't polarized because most airplane canopies are, and at certain angles you'd see only black. I don't know if canopies are polarized, but I do know two polarized surfaces will block out all light in the right conditions. > Years ago my uncle (then a pilot in the US Air Force) told me that the > aviator sunglasses they're issued aren't polarized because most airplane > canopies are, and at certain angles you'd see only black. I don't know if > canopies are polarized, but I do know two polarized surfaces will block out > all light in the right conditions. I quit buying polarized glasses and sunglasses a while back because they make it impossible to see the screen on my GPS or my radar detector.  SignaturePostulate a group whose intent is to destroy the United States from within via anarchy and bankruptcy. The actions of the United States Congress are completely consistent with the actions one would predict from such a group. >>I was reading about this idea today. If all headlamps >> are fitted with a polarizing filter, then other drivers can [quoted text clipped - 14 lines] >canopies are polarized, but I do know two polarized surfaces will block out >all light in the right conditions. Edsels came with polarized windshields and some people had that problem when they wore Polarized sunglasses. > >I was reading about this idea today. If all headlamps > > are fitted with a polarizing filter, then other drivers can [quoted text clipped - 4 lines] > You wouldn't eliminate the glare, you could completely eliminate the light > altogether. Probably not a good idea. Obviously you would have some sort of standard for the angle of polarization, so that enough light gets through so you can see the approaching vehicle. You could avoid the sunglasses problem by having the headlights emit some light polarised at one particular angle, and other light at a different angle, >> >I was reading about this idea today. If all headlamps >> > are fitted with a polarizing filter, then other drivers can [quoted text clipped - 12 lines] >the headlights emit some light polarised at one >particular angle, and other light at a different angle, My uncle Robert patented a workable system back in the sixties, and tried to sell polarized filters for headlights and a flip-down polarizer for the visor. The idea here is that it blocks out the direct light of the oncoming headlights, but that reflected light has been Faraday-rotated and does not get blocked. The problem, of course, is that everybody else on the road needs to install polarizers and convincing them to do so (or the car manufacturers to do so) is nontrivial. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > I was reading about this idea today. If all headlamps > are fitted with a polarizing filter, then other drivers can [quoted text clipped - 12 lines] > Is anyone producing such a thing commercially > at the moment? Headlights serve two purposes: 1. At night they allow the driver to see the road. 2. At all times they allow other drivers to see an oncoming car. Why would you want to reduce and possibly eliminate the obvious improvement in safety from #2? |
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