Below are some instructions for converting a web cam to for cheap, easy infrared photography.
Basically, all digital cameras are capable of detecting infrared
radiation just outside of the visible spectrum. That is to say light
with a longer wavelength than the red end of the spectrum. With some
slight modification we can filter out the visible light and let through
the infrared light. This will not allow you to do thermal imaging,
which is done in the far infra red.
The video to the right shows what happens when you simply put a filter suitable for infrared photography in front of the web cam. It works, but the results are much better if you put the filter inside the camera instead.
If you're interested in doing infrared photography "right" then you should look at this tutorial by Eric Chen rather than read further.
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Two screws. Very easy.
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The web cam I used was designed for use in low light. It includes six IR LEDs. More importantly, since it was designed to work with IR LEDs it lacks the IR filter that most digital cameras include. The IR filter found in digital cameras helps keep colors more consistent at all light levels. Consequently it blocks most of the light we're interested in for this project. More recently I got a new web cam. I actually got it for free, it came bundled with a USB headset I bought. It was also pretty easy to modify. Here are the pictures documenting it.
Careful not to break the microphone wires.
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The filter. Exposed color film negative. Just that bit at the end of a roll
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As I mentioned above, the camera lacks an IR filter, but we need to add a visible light filter. For this project I used exposed color film negative. These days you may have to dig around a bit to find any. In the past I've used a piece of a 3.5" floppy (I've stockpiled some for future use). The actual disk part does a good job of filtering out visible light, but it didn't seem to work well with this camera. I recommend you plan on experimenting a little.
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Just cover the ccd with the filter. If you make it big enough it won't matter if it moves around a little. It will still cover the ccd. You may need multiple layers. I used two layers of exposed negative, but when I go outside it is still too bright. I thought about going to three layers, but two seems about right for use in my classroom.
When you're done just close it up and put your two screws back in.
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Plants tend to emit lots of near IR. Hence they look white.
This picture was taken out the window of my classroom.
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Black Absorbs all colors?
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Apparently not near infrared! Taken with a 60W incandescent bulb as the light source.
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As I've said repeatedly I'm cheap and lazy, which is why I chose the camera I did. As it turns out I received a second webcam for free. So I broke it too. I took a bunch of pictures so can see how it's different. The main difference is that it included an IR filter. That just had to go. Here are some instructions for modifying other cameras to do the same thing:
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