I chose an old Intel CS330 webcam, no more recent than 1998 (yeah, it's pretty old-skool). You'll also need some exposed camera film, a small screwdriver, and a knife.
The basic plan is to open up the webcam, remove the lens housing, remove the Infrared filter from the lens, and replace it with film to filter visible light. Be prepared to damage the webcam--I did not have any problems taking mine apart, modifying, or reassembling, but I cannot vouch for other models.
- First we'll remove the case of the webcam. Take off any mounts, unscrew any screws, and otherwise pry the case off. Try not to break any clips, but instead gently remove them with a screwdriver. I also unscrewed and unclipped the USB cable from the circuit board, just to get it out of the way; be careful not to bend any pins.
- Next unscrew the lens assembly from the circuit board, and unclip it from the mount. Now the CMOS sensor on the circuit board is exposed, so be careful not to scratch it, get dust on it, or even touch it.
- If you're lucky, there should be a small red piece of glass against the lens that is the IR filter. Simply remove it. If you are unlucky like me, the filter was painted directly onto the lens. Gently scratch (I know it sounds terrible) the lens with the tip of a knife blade until the red coating flicks off. This is the most difficult part; you need to apply enough pressure to chip off the filter coating, but avoid scratching the glass beneath. I found that it requires more pressure on the knife than you might expect, but it is better to be cautious.
- Cut a piece of exposed, black photographic film to cover the lens; this will filter visible light, but allow IR wavelengths through. Use film that is as dark as possible, and that does not have a picture negative on it. One can usually find such pieces at the beginning of the roll, before actual pictures have been taken.
- Use a single fiber of duct tape (one of the grey strings), and lay it over the edge of the lens. Push the film you cut onto this to hold it in place. It will not be the "tightest" of seals, but it will prevent glue from getting caught on the lens, etc. Reassemble the lens mount.
- Screw the lens assembly back onto the circuit board. Before doing this, blow gently on the CMOS sensor to remove any dust specks that will greatly degrade picture quality. Continue to replace the board in the case, reattach the USB cable, and close the case back up. Don't forget to screw in the screws.
That's it. Now plug your webcam back into your computer and use it like you always have. Except now, the images will be in the IR spectrum. At first glance it will simply look like a black-and-white image of the regular shot, but look closer. You will see that some inks and dyes remain transparent, and others show up nicely. Take a look at a dollar bill, or your arm (the arm is weird--all the veins show up).
If the image looks too dark, you may need a stronger source if IR light. Daylight is normally sufficient, and occasionally an incandescent bulb will overlap into the IR spectrum adequately. However, try pointing a TV remote at the subject and holding down a button if you need more light.
PS. Thanks to for the image hosting.