How to Convert a Digital Watch to a Negative Display

Re:How to Convert a Digital Watch to a Negative Display by jrajav on Monday April 21, 2014 @03:45PM (#7623208)

> 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...

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Re:How to Convert a Digital Watch to a Negative Display by jsingleton on Monday April 21, 2014 @04:11PM (#7623441)

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.

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Re:How to Convert a Digital Watch to a Negative Display by rcxdude on Monday April 21, 2014 @04:21PM (#7623526)

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

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Re:How to Convert a Digital Watch to a Negative Display by superuser2 on Monday April 21, 2014 @05:04PM (#7623862)

3M sells this.

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