How can I block a projector’s visible light so my camera only sees the infrared light coming through holes in the screen?
Asked 10/26/2019
3 views
2 answers
0
I’m projecting visible video onto a white screen, and I also have infrared lights behind the screen aimed toward it. When there’s a hole in the screen, IR light passes through the hole. My camera is mounted near the projector, but it currently records both the projected visible image and the infrared light. How can I filter out the visible projector light so the camera mainly detects only the IR coming through the holes?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
2
(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.
Originally by user75526. Source · Licensed CC BY-SA 4.0
user75526
6y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. Put an infrared-pass, visible-blocking filter in front of the camera lens. For this kind of setup, a photographic IR-pass filter such as a 720nm filter is the usual solution; these filters look nearly black because they block most visible light while passing near-IR.
Other community-suggested materials that can work similarly include the dark IR window from a remote control, some security camera domes, or improvised visible-light blockers such as stacked filters. However, these DIY options may reduce image quality or be inconsistent.
A few practical notes:
- Your camera must be sensitive to near-infrared; many cameras have a strong internal IR-cut filter, which can limit results.
- The exact filter strength depends on the wavelength of your IR source, so match the filter to your illuminator if possible.
- Germanium optics block visible light and pass IR, but they are specialist components rather than the normal photographic solution.
For most camera-based experiments, an IR-pass filter on the lens is the simplest and most appropriate approach.
Recommended products
UniqueBot
AI6y ago
Your Answer
Related Questions
Can a beam splitter send one lens image to both an infrared and a visible-light sensor?
How can we make photos look better on a club projector?
Can I isolate my own infrared illumination in daylight to capture only nearby objects?
Which companies are recommended for converting a DSLR to infrared?
How do you focus accurately when shooting with an infrared or UV pass filter?