Polarised Window Filters: Block Light from All Directions?

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In summary, the conversation discusses the use of 2 sheets of glass as a window with 2 polarizing filters acting as blinds sandwiched between them at 90 degrees. The filters can be controlled remotely to block light at different levels. It is mentioned that the incidence angle may affect the effectiveness of the polarizers. The use of liquid crystals as an alternative is also mentioned, with the reminder that the technology has been adapted for welding glasses. ND filters are suggested as a cheaper option for blocking all light evenly. The conversation concludes with a discussion on the angle-independence of LCD panels.
  • #1
MIKEBROCK
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Would it be possible to use 2 sheets of glass as a window, within the 2 sheets of glass are 2 polarising filters, acting as blinds sandwiched in the glass, at 90degrees from each other. By remote the polarised lens can ascend or descend up and down the window blocking light at different levels. Letting no light come through the window, and only a bit of light through window or all light. Would this work from all directions outside the window?
 
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  • #2
I don't understand what "the polarizing lens" is supposed to be. If you have a circular window and there are two polarizing foils of which you can turn one, then you should be able to adjust the transmission between close to 45% and 0% because the first foil will cut out half of the light, and the window reflects about 4%. The incidence angle should not matter much, but you may see that you can suppress or enhance light that is reflected of clean surfaces like puddles since that tends to be polarized. With two 90 degree foils and a third one that you can turn in between for "magic transmission" at 45 degrees, you will be able to adjust the light intensity between under 3% and 0%
That is pretty dark.
Transmissions (maximum case):
window 96%
polarizer 50%
45 deg polarizer 25%
polarizer 25%
window 96%
 
  • #3
MIKEBROCK said:
Would it be possible to use 2 sheets of glass as a window, within the 2 sheets of glass are 2 polarising filters, acting as blinds sandwiched in the glass, at 90degrees from each other. By remote the polarised lens can ascend or descend up and down the window blocking light at different levels. Letting no light come through the window, and only a bit of light through window or all light. Would this work from all directions outside the window?

Polarizers generally work at restricted angles of incidence, so the effect would only be partial. Kent State's Liquid Crystal Institute developed a similar device- the transmission was controlled by altering the retardance of a thin liquid crystal layer, and could be switched very rapidly:

http://www.lci.kent.edu/switch.html [Broken]

IIRC, the technology has been adapted for welding glasses.
 
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  • #4
It's much easier just to use a standard window shade.
 
  • #5
thanks for the help, and sorry for the very late reply. So it would not be possible as an everyday window due to the variation in incidence angle? Seems to be a conflict in answers here, thank you anyway.
 
  • #6
Again, I do not think that the incident angle matters much. Just get two pairs of 3D glasses and hold them over one another such that all light is blocked. (you might have to flip the direction) I do not think you get light through even at low angles. Liquid crystals are another matter, there the incidence angle matters much more as you see with TFT displays.
I think the polarization is the least of your problems. The way you describe it, you have the same effect just with an ND filter and much cheaper at that.
 
  • #7
ok thankyou, good idea i will try that. Do ND filters block all light though?
 
  • #8
ND Filters block all light evenly, they are basically shades.
 
  • #9
0xDEADBEEF said:
Again, I do not think that the incident angle matters much. Just get two pairs of 3D glasses and hold them over one another such that all light is blocked. (you might have to flip the direction) I do not think you get light through even at low angles. Liquid crystals are another matter, there the incidence angle matters much more as you see with TFT displays.

Even with displays, it depends on the technology. Good LCD panels are pretty much angle-independent. Only the inexpensive (TN) panels have substantial changes with viewing angle.
 

1. How do polarised window filters block light from all directions?

Polarised window filters are made of a special material that contains microscopic crystals aligned in a specific direction. When light passes through the filter, the crystals only allow light waves that are aligned with their direction to pass through, while blocking all other light. This results in the filter effectively blocking light from all directions.

2. Can polarised window filters block all types of light?

Polarised window filters are most effective at blocking horizontally polarised light, which is often the type of light that causes glare and reflections. However, they are less effective at blocking vertically polarised light and may not be as effective at blocking other types of light such as UV rays.

3. How do polarised window filters reduce glare?

Glare occurs when light reflects off of a surface and becomes polarised in a specific direction. Polarised window filters block this horizontally polarised light, reducing the amount of glare that reaches our eyes. This allows us to see objects more clearly and reduces eye strain.

4. Are polarised window filters only useful for sunny days?

Polarised window filters are most commonly used to reduce glare and improve visibility on sunny days. However, they can also be beneficial on cloudy days, as they can reduce the amount of scattered light that enters through the windows and provides a clearer view.

5. Do polarised window filters affect the color of light?

Yes, polarised window filters can affect the color of light that passes through them. This is because they selectively block light waves based on their direction, which can alter the overall color composition of the light that enters through the filter. This can result in a slight color shift, but it is typically not noticeable to the human eye.

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