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I have a video projector, projecting a video on a white screen (white paper), behind the screen there is two infrared light facing towards the screen, when there is a hole in the screen the infrared light comes out from the hole, I've got the camera on top of video projector, what I want to do is something, the camera should only detect the infrared light that comes out from the hole on the screen but not the actual video projecting by the projector, please give me suggestions to filter out visible light and get on infrared light behind the screen when it comes out from hole, currently camera is capturing infrared and visible video frame what I don't want to happen. HELP!!!!!

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    \$\begingroup\$ What is the final goal? Why do you want to capture the infrared light? \$\endgroup\$ Commented Oct 26, 2019 at 15:13
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    \$\begingroup\$ This doesn't seem like a photography project. There are filters that block visible light and allow IR through. Try searching for "IR 720nm". \$\endgroup\$
    – xiota
    Commented Oct 26, 2019 at 15:38
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    \$\begingroup\$ There are regular camera filters called infrared. Read it carefully, these are of two types, passing infrared but blocking visible light, or a few are the opposite, passing visible and blocking infrared. And digital camera sensors often already block infrared, to represent better what the human eye sees. \$\endgroup\$
    – WayneF
    Commented Oct 26, 2019 at 15:43
  • \$\begingroup\$ @SaaruLindestøkke I want to detect hole of infrared. but camera is showing not just the infrared but with video projecting on the screen \$\endgroup\$ Commented Oct 26, 2019 at 16:06
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    \$\begingroup\$ Filters are never "perfect", but there are many regular camera filters that block visible light and pass infrared. amazon.com/s?k=infrared+filter \$\endgroup\$
    – WayneF
    Commented Oct 26, 2019 at 16:13

2 Answers 2

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(Near) IR pass filters are everywhere. For photographic filters, try searching for "IR 720nm". It's easy to tell which are the right ones because they will look black. Some other options that also block visible light and pass IR:

  • Disassemble a remote control and put the plastic IR pass filter over your lens.
  • Use a security camera dome.
  • Cross photographic polarizing filters. (Linear is easier. Circular works if one of them is facing the wrong way.)
  • Break apart a cheap pair of polarizing sunglasses and cross the lenses.
  • Stack ND filters.
  • Stack several different color filters (red + green + blue).
  • Use developed, exposed negative film or developed, unexposed reversal film. (Pretty bad image quality, but may be artistically interesting.)
  • Use the magnetic disk from a floppy disk. (Horrendous image quality, but can be fun.)

  • Purchase an IR capable camera with the correct filter already installed.

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The ideal material for working with infrared radiation (lenses, prisms, windows, etc.) is germanium which does not pass visible wavelengths. If you cannot find what you want in lens catalogs, you can have most anything made to order.

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