Can LEDs emit polarized light?
Read an article back in the 1970's that proposed the use of polarized light filters on automobile headlights combined with polarized filters lights on windshields. The notion was to block glare from the headlights of oncoming cars, while allowing through light reflected from your own headlights.
If you have ever gone driving at night on a twisting two-lane road with lots of oncoming cars, the merit of this idea is clear.
The downside is that polarized light filters on headlights is a very inefficient solution. The filter is going to block most of the light, meaning you need much stronger lights to get the same amount of light on the road. Much stronger lights means greater cost, and likely a lot of heat buildup in the headlight/filter assembly.
If the light source itself emitted polarized light, then the efficiency problem would be gone. LEDs are starting to get bright enough to be considered for headlights. Is it possible to fabricate an LED that emits polarized light?
I have a vague memory of reading about LED's or some other solid-state device that emitted polarized light, but have no idea how to track down this notion.
If LED headlights could be required to emit polarized light (45 degrees off vertical), then after perhaps a decade you could wear inexpensive glasses with polarized filters, and driving on backroads at night would be a lot safer.