Car Windshields are not polarized!

[dioptical]

Right? I would think so, because if you were to turn a corner and just turn your head other than 90 degrees...then everything would turn black or close to it.....

I called car companies and glasses companies....some say yes and some say no.....I just think that they dont know what polarized means or is......

I called the Maui Jim rep and he said that windshields are not polarized.......

I have staff memebers saying that windshields are polarized and I dont know where they got that from.....:angry:

But before I say anything I want to make sure that they arent and a good explaination for why that is.:shiner:

Thank you in advance for the comments.

[Striderswife]

I have no official information, or documented research on this, but only my own experience. On very, very long road trips I would tilt my head around to relieve strain on my neck. If I tilted my head left or right, the road ahead of me would lighten or darken in shade. It's not something I experience out in the open, and it doesn't happen if I'm driving my husband's truck. Does that mean my windshield is polarized? I'm anxious to see what others have to say, too!

[chip anderson]

Polarized lenses are made to stop reflected glare. If you turn the lens with or without your head, the glare being reflected in the 180 degree plane is no longer blocked.
Now if you have two polarized surfaces and turn them 90 degrees opposed to each other the light at 90 and 180 as well as any other direction becomes totally blocked. i.e. things go dark.
Now the simple answer to your question is automotive and most other windshields are not polarized although many contain UV filters.
You can test this, just take a polarized lens and hold it away from your face and turn it 90 degrees , if things didn't go dark, it's not polarized.

Chip

[KStraker]

I have no official information, or documented research on this, but only my own experience. On very, very long road trips I would tilt my head around to relieve strain on my neck. If I tilted my head left or right, the road ahead of me would lighten or darken in shade. It's not something I experience out in the open, and it doesn't happen if I'm driving my husband's truck. Does that mean my windshield is polarized? I'm anxious to see what others have to say, too!

No, your windshield has a gradient tint, like most do. I don't think polarization can be accomplished without the help of the aptly named polarizing film layer. I've never seen a polarized window. Google comes up with a couple companies who make polarized film for home windows. It's a sheet of tinted material you apply like an auto tint.

[drk]

With oncoming windshields (not yours) viewed with polarized lenses, certainly the angle that your lens orients to the windshield will make a difference whether you see a reflection (glare) or not.

But, as mentioned, that's just the normal polarization effect. You can do this when looking at the surface of a pond.

If the windshield of your car or the oncoming car were truly polarized, at a certain angle the windshield would look black. That obviously would be a hazardous situation.

Here's what I want to know: If you look at rear windshields with polarized lenses on, you will see a checkerboard pattern! I'm not sure if they change with angles of orientation, but I think what happens is that the "clearer square" and the "darker square" will alternate with polarized filter orientation.

It's almost as if there is indeed a polarization filter on rear windows, but its in varying orientations so that there are always clear squares to see through, regardless of head angle. Can this be? How would they effect (affect?) this?

Another note: with polarized lenses, GM vehicles' windshields look purpley. No other manufacturer has that.

[KStraker]

Here's what I want to know: If you look at rear windshields with polarized lenses on, you will see a checkerboard pattern! I'm not sure if they change with angles of orientation, but I think what happens is that the "clearer square" and the "darker square" will alternate with polarized filter orientation.

It's almost as if there is indeed a polarization filter on rear windows, but its in varying orientations so that there are always clear squares to see through, regardless of head angle. Can this be? How would they effect (affect?) this?

You are seeing the tempering pattern in the glass. It's the same as checking for the Maltese cross on tempered glass lenses to verify the tempering. Take a look at this:
http://images.google.com/imgres?imgu...3DfDl%26um%3D1

[drk]

That makes sense! Note that the dark and light areas could form a checkerboard pattern...

Good find.

[DragonLensmanWV]

That makes sense! Note that the dark and light areas could form a checkerboard pattern...

Good find.

Multiple small air nozzles over a large piece of glass give you that effect. It's actually multiple adjoining Maltese crosses made by birefringence.

[chip anderson]

Actually I think Ford and some Japanese rear windows are lain on a checkerboard metal frame with holes for cooling after being heated for curving and tempering. This results in the checkerboard marks and uneaven tempering.
Usually not seen on GM rear windows.

Chip

[Chris Ryser]

Pola Visor, auto sun visors, windsheld visors

Pola Visors,

Pola Visors, removable "see-through" auto sun visors created to enhance driving vision, comfort, and reduce eye strain. Its the first polarized auto sun visors for driving and has been made to meet impact resistance regulations set by the FDA. Pola Visor benefits like polarized sunglasses, but as car windshield visors.


http://www.autostreak.com/polavisor/index.htm

[dioptical]

Pola Visor, auto sun visors, windsheld visors

Pola Visors,

Pola Visors, removable "see-through" auto sun visors created to enhance driving vision, comfort, and reduce eye strain. Its the first polarized auto sun visors for driving and has been made to meet impact resistance regulations set by the FDA. Pola Visor benefits like polarized sunglasses, but as car windshield visors.


http://www.autostreak.com/polavisor/index.htm

Nice to see that they pulled over to take the picture!!!!!!!!:bbg:

[Ory]

Another note: with polarized lenses, GM vehicles' windshields look purpley. No other manufacturer has that.

I've noticed that too. I've always wondered if it is their UV treatment - reflecting rather than absorbing.

[Uilleann]

Automotive windshields in the USA are not polarized. I can't speak with any direct experience to the rest of the cars on the planet, but I would guess that it's likely a 99.999% certainty that no other cars are either.

The checkerboard pattern you describe is due to the tempering of the glass, and that is something that most all vehicle's back windows exhibit here. Some to a greater and some to a lesser extent however.

The purple color cast you see (something like a very strange A/R color cast right?) is indeed a treatment used to (according to the manufactures) help limit UV exposure inside the vehicle. There are also gold and blue variants, and it is fairly widely used - or has been in the past. Mercedes, Buick, Cadillac, Pontiac, Jaguar and Audi have all been spotted here with the UV treatment. Some come factory direct, others you can purchase that way aftermarket.

Some aircraft windscreens use a heavy lamination process that can show interference patters when viewed with polarized sunglasses on - Similar to the rainbow appearance some aftermarket window tint films show. However, they are also not polarized. There are some military aircraft that use a coating of Indium Tin to enhance radar reflections from their windscreens and make them a bit more stealthy such as the F-117, F-16 and F-22 among others.

Hope that helps a bit.

As for your employees telling patients that windshields are polarized - you may want to put a stop to that asap.

:cheers:

[drk]

Geez, uilleann, you know just about everything :cheers:

[Craig]

Actually I think Ford and some Japanese rear windows are lain on a checkerboard metal frame with holes for cooling after being heated for curving and tempering. This results in the checkerboard marks and uneaven tempering.
Usually not seen on GM rear windows.

Chip

What does the word indecorus mean? It related to a plant on google.

Craig

[chip anderson]

Craig:

Ask Mr. Fesmire?

I think it means completely lackin in social discression or failing to put ones thoughts in the most polite form.

Chip

[DragonLensmanWV]

Actually, the reason some GM cars and vans have a purplish coating on the windshield (and some Fords with a gold windshield) because they use a thin metal plating on the inside of the windshield which is an electric defroster/demister similar to the thin gold plate used on the inside of astronaut's facemasks to keep them fog-free.

[Uilleann]

Geez, uilleann, you know just about everything :cheers:

Hardly! LOL :shiner: But I've spent a good deal of time around enough varied people to have a head full of useless facts about some of this stuff. We can buddy up on the "Useless Trivia" column for $500 please Alex. ;)

Polarization is one of those things that seems just about anyone who's ever worn a pair, or even seen some ridiculous infomercial on late night TV instantly becomes an expert. There seem to be so many in the "business" (sporting goods stores to MD's offices etc.) who just regurgitate what the training manual/co-worker/boss/commanding officer/whoever told them without having any real understanding of the filter, or how it really works - and doesn't work.

Just hope I can help to clear the air a tiny bit for some. Cheers! :cheers:

[Fezz]

What does the word indecorus mean? It related to a plant on google.

Craig

Sexton Mountain Mariposa Lily


:cheers::cheers::cheers:

(Unless you speak Latin...Than Chip is on Target!)

[Uilleann]

Actually, the reason some GM cars and vans have a purplish coating on the windshield (and some Fords with a gold windshield) because they use a thin metal plating on the inside of the windshield which is an electric defroster/demister similar to the thin gold plate used on the inside of astronaut's facemasks to keep them fog-free.

Uh - OK, sorry gotta add a bit of correction here. The 24k gold film used on the EVA suits from Apollo to present is not any sort of anti-fog/frost/mist device. It is there to keep the occupant's face from burning off. Cosmic radiation in low earth orbit - lunar orbit/surface is intense, to say nothing of the massive temperature swings from sunlight to shade (over 500 deg. F typically). The gold layer was used to block this radiation and intense heat. The suits general thermal controls and de-humidifying systems are a separate system altogether housed in the backpack. The orange "pumpkin suits" that are used for launch/re-entry are a more standard pressure suit, and use a more common tinted visor (grey?) but without the gold layer.

When I was working with some auto glass companies in years past, I was told that the blue/purple/gold glass was used primarily to enhance the efficacy of the vehicle's A/C. But that it did nothing to enhance vision, or reduce fogging. Some vehicle's (Land/Range Rover's and some high end BMW's come to mind) do use a very thin system of wires in the windscreen similar to the rear window defogger lines in most cars. With the difference being the wires are embedded into the glass itself, and are very fine (think hair's breadth or possibly even a bit smaller). Using an electric current, they remove fog by the same heating mechanism that operates rear window defoggers.

Hope that helps a bit!

[drk]

Don't mess...


...with Uilleann!!!

[DragonLensmanWV]

Uh - OK, sorry gotta add a bit of correction here. The 24k gold film used on the EVA suits from Apollo to present is not any sort of anti-fog/frost/mist device. It is there to keep the occupant's face from burning off. Cosmic radiation in low earth orbit - lunar orbit/surface is intense, to say nothing of the massive temperature swings from sunlight to shade (over 500 deg. F typically). The gold layer was used to block this radiation and intense heat. The suits general thermal controls and de-humidifying systems are a separate system altogether housed in the backpack. The orange "pumpkin suits" that are used for launch/re-entry are a more standard pressure suit, and use a more common tinted visor (grey?) but without the gold layer.

When I was working with some auto glass companies in years past, I was told that the blue/purple/gold glass was used primarily to enhance the efficacy of the vehicle's A/C. But that it did nothing to enhance vision, or reduce fogging. Some vehicle's (Land/Range Rover's and some high end BMW's come to mind) do use a very thin system of wires in the windscreen similar to the rear window defogger lines in most cars. With the difference being the wires are embedded into the glass itself, and are very fine (think hair's breadth or possibly even a bit smaller). Using an electric current, they remove fog by the same heating mechanism that operates rear window defoggers.

Hope that helps a bit!

Actually, at least the Ford gold windshield IS for near instant defogging, as it was heavily promoted for that purpose at the time. My father got a Crown Vic with that feature. You could start up and if it was humid and the windshield fogged, you push a button and the windshield would clear in about three seconds.They just deposited it thick enough to hold a current across it, but thin enough to see through. I was told by someone who had a Pontiac van with the purple windshield that it also performed the same function.
You are correct about the secondary use of radiation shielding with the gold visor, but they do also pass a current through it to keep it clear.

[Uilleann]

Actually, at least the Ford gold windshield IS for near instant defogging, as it was heavily promoted for that purpose at the time. My father got a Crown Vic with that feature. You could start up and if it was humid and the windshield fogged, you push a button and the windshield would clear in about three seconds.They just deposited it thick enough to hold a current across it, but thin enough to see through. I was told by someone who had a Pontiac van with the purple windshield that it also performed the same function.
You are correct about the secondary use of radiation shielding with the gold visor, but they do also pass a current through it to keep it clear.

Ok, ok - I'll grant that there may be some defogging property claimed by the auto makers in this case - however, the information I was able to find through a (granted - quick) Google search states that the "nanotechnology" is embedded into the glass itself - which would be different from some form of exterior film or coating to help prevent fogging. I'm unclear as to the ability of this new "nano-glass" to conduct a current. Certainly seems plausible I would think.

But the info on the US astronaut visor is not correct. The glass (actually a polycarbonate derivative in early suits - not sure on modern that separates the wearer from the vacuum of space in the current EMU (Extravehicular Mobility Unit) is clear. There is a secondary sun visor (the gold one) that can be pulled down or retracted as needed - common in low earth orbit as you move from sun to shade approx. every 45 minutes. But it is completely external, has no contact with the astronaut or their self-contained "atmosphere". Although...I'm still not sure why someone hasn't invented an interior windshield wiper when they sneeze! :shiner::shiner::shiner: (Man - a decade at the local planetarium certainly didn't do a thing to cure me of any space nerdiness did it?! LOL)