Windows in toilet doors

Toilet doors typically don't have windows to ensure privacy. Additionally these doors typically come in pairs to ensure adequate separation from other areas. (I'm talking about the doors to the toilet facilities, not the door to a cubicle.)

A downside of the lack of windows is that people can be hit by a door by someone coming from the other direction.

However, it should be possible to address this by the use of polarising filters. If a window is placed in each door an perpendicular polarising filters are placed on each window, then light from within the toilet room would not make it through both windows. However, light from within the gap between the two doors would be able to exit both windows, ensuring that people are not hit by others opening the doors.