There are several general tutorials on the web for making (near) infrared cameras, but you might get lost picking a webcam and the directions you found might be different for your webcam. So, here are specific directions for a specific webcam with three priorities in mind: It's fast, it's cheap, it works. (BTW, this is meant to be an educational tool for physics classes, but I'm sure you can use it for plenty of other stuff.)
- Cheapie webcam from Amazon.com (http://www.amazon.com/gp/product/B0015TJNEY) ($5-6)
- 1 or 2 (recommended) pieces of exposed film negatives (as visible light filters)
- Sharp craft knife ("X-ACTO knife")
- super glue (cyanoacrylate), or any glue will do
If you're lucky and find someone really nice at a photo place, they might give you exposed film negatives for free. To my knowledge, all this is is if you took a roll of film, pulled it out of the roll to expose it to light, then got the negatives of those. You might have some sitting around if you have old negatives... they're likely the dark pieces at the beginning of the negatives. Back in the days when we used film.
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Step 1: Disassemble the Lens
Use your fingers to unscrew the lens fixture (counter-clockwise) as far as it will go.
Use the screwdriver (or screwdriver-like implement) to press in the "tabs" to remove the outer assembly.
Continue using your fingers to unscrew the inner assembly until it comes out.
Step 2: Remove Infrared Filter
Inside the lens fixture is a square, light blue piece of glass (or something). Remove this IR filter to let in more infrared light.
1. Use your sharp knife to shave off the plastic holding down the corners of the IR filters.
2. Once the plastic is removed, you should be able to easily lift the filter out (using your knife)
Update: The webcams you get may vary (even if you bought it from the link I listed earlier). Different webcams may have been constructed slightly differently, and removing this IR filter may be easier or harder. Cross your fingers. :oP
Step 3: Insert and Glue Visible Light Filter
1. Cut out two pieces of your visible light filters (exposed film negatives). They should fit right into the square.
2. Plop the filters into the square, where the IR filter used to be.
3. Glue it down using your preferred method. (I dipped the tip of a paperclip in the glue, then scraped it onto the edge of the film. Do not squeeze super glue directly onto the film, as it'll probably be too much and flood over the whole thing. Super glue is tricky to work with. Use tiny amounts, and if that's not enough, use more. Or just use regular school glue. These filters won't be undergoing much load or stress.)
Step 4: Reassemble
Put it all back.
Step 5: Test It Out
Plug it in and test it out. If you don't have any webcam software, try Yawcam, free webcam software for Windows.
For lesson ideas, see Dan Burns' handout here: http://www.lghs.net/apps/classes/show_class.jsp?classREC_ID=398988 (the IR one near the bottom)
The topic of infrared itself isn't a California Science Content Standard, but I use it as a bridge to go from visible light to "invisible light", then expand it to the idea of a giant range of "invisible lights" known as the electromagnetic spectrum, which is specifically a standard. I have no evidence this approach is effective. :oP :o)