> I wonder how practical it would be to make a private display by removing the polarising film from it and then viewing with polarised glasses.

It's been done, pretty much how you'd expect:

http://www.instructables.com/id/Privacy-monitor-made-from-an...

There are quite a few hacks around but I wondered if there was some reason these aren't more widespread or commercially available. Business idea?

You could also make something that filters all light but near infra-red so it could be seen by CCDs (on cameras or phones) but not with the human eye. Or do the reverse and flood the picture with near infra-red to prevent it being photographed.

I think you can buy this kind of thing, I've seen them in use in some offices where sensitive information is being viewed.

3M sells this.

I was really excited to read the idea about advert blocking, but when I donned my glasses, this is what I saw:

http://blog.ctnews.com/meyers/files/2010/11/lethem2.jpg

;)

>I wonder how practical it would be to make a private display by removing the polarising film from it and then viewing with polarised glasses.

In Japan a lot of people have "privacy" screen protectors on their cells that basically make the viewing angle very small. I always assumed it was through some form of polarization though now I'm not sure.

http://www.trendhunter.com/trends/mobile-privacy-screens-kee...

They probably have the same effect as an LCD with a very narrow viewing angle. Modern displays have a pretty high viewing angle; older ones start to change color and become illegible when viewed at an angle. I've seen the same thing on ATMs and the like.

Anyone wishing to try this should use proper polarised glasses, though, rather than repurposing filters. They're not protective from UV, you see.