[PaulQ]

How does the rear view mirror work? I mean technically, not how to operate it.

Why would you ever turn it off?

 

[Gonzo]

I could be wrong but I think its as simple as the mirror has a LCD screen whitch darkens based on the light sensor from head lights behind you.

I guess the switch is there as with anything automated there might be need to over ride it for safety reasons.

 

[bob1]

I sat there and gave some thought and said what is the point of on-off for day/night. When it is on, it's not any darker in the day??? I really don't know the mechanics of what makes it work but it is not as dim as say a good old fashoned move with you hands mirror.
I have no clue why it is an option to turn it off.
Bob1

 

[Kris]

Gonzo is right.

Why option - aren't we obsessed with options? The more the better......

 

[GripperDon]

Their are 2 light sensors. One aimed to the front to tell how much daylight there is. The second aimed to the rear to detect the amount of light from the headlight behind you. If you block up the front sensor the mirror will max out it darkening capability. Basically that is it. Some mirrors have adjustments. You can also glue a little spherical lens over the, to the rear, sensor to increase it's light gathering capability.

GRIP

 

[zebelkhan]

Does anyone know how the mirror gets dark? I mean is there an angle change....photo sensitive film....what....?

 

[GripperDon]

basically a voltage is applied to an electrically conductive film to cause that thin films molicules to "lign up" with the voltage field this rotation in effect allows only light of that polarization to pass. This film is place over a fixed polarization film. The interplay of the two regulate the amount of light that can pass thru. Take a look here for more info. http://www.colorado.edu/physics/2000/polarization/
GRIP

 

[zebelkhan]

Much like some eye glasses except it uses electricity. That is how you can turn it off. Good info. Thanks Grip for the link as well.