A cool property of NIR filters is that they are able to produce a relatively recognisable picture of the world with all screens (TFT, projected) filtered out. I&#x27;ve used this in the past for computer vision to do object recognition on top of a projected display without having to programmatically filter out the projection.<p>It&#x27;s also pretty easy to make a rudimentary NIR filter by layering a red, green and blue filter on top of each other: the resulting filter will not allow any visible light through (e.g. red, green or blue), only the &quot;rest&quot;.<p>edit: and they make your eyes look really creepy too (not me in the picture btw): <a href="https:&#x2F;&#x2F;flic.kr&#x2F;p&#x2F;6CYzDZ" rel="nofollow">https:&#x2F;&#x2F;flic.kr&#x2F;p&#x2F;6CYzDZ</a>