I’ve started working on a project to perform low cost eye tracking. As part of this project I need to have an infra-red (IR) camera. So I’ve converted an old Apple iSight firewire webcam in a camera sensitive to IR light. In this post I describe how to convert the iSight camera to work with IR light.

It is very easy to do. An IR camera is also useful for for night visions application or even to see through clothing (some proud husband shows off his wife’s breasts on youtube). In this post I’ll describe how I converted the iSight. I was inspired by HoagiesHouse.com but it seems that there are lots of sites covering this topic (I found this one after I’d finished mine).

It turns out that a regular CCD is sensitive to IR light and so most webcams and digital cameras place a filter in front of the CCD which blocks incoming IR light. It does a pretty good job, although you can still see your TV remote flashing if you point it at the camera usually. To convert a camera you just need to remove the IR filter and put in a visual spectrum filter to block other light.

What you need:

• An iSight camera
• A phillips cross head screw driver size 00
• fine tweezers
• A small piece of unexposed, processed print film (for the visible light filter)

Step 1: Open the iSight

1) remove the two screws on the bottom and unclip the white plastic surround.

2) Slide off the outer metal casing by pulling it away from he lens end.

3) Peel off the fabric and use your tweezers to unclip the black plastic lock so you can release the "J2" wire

4) Unscrew the three screws holding the plastic case to the lens assembly (two on top one below)

5) Undo the 6 plastic clips holding the two pieces of the plastic case together. Then use tweezers to undo the lock holding the wide ribbon cable to the main circuit board and lift off the CCD and lens assembly.

6) Release the ribbon cable from the CCD board and undo the three screws holding it to the lens assembly.

You should now have access to the IR filter. It is a small piece of glass with a red tint to it. The red tint is what filters out the IR light. If you just removed the glass the camera becomes short sighted, instead you need to remove the film from the glass. I managed this by scraping it with my thumb nail for a while with some hot water and dish soap. Nothing seemed to happen for a while, but then it came off in little bits. You should be able to completely remove the red tint from the glass. It is probably best not to use anything hard which could scratch the glass. One person suggested that you use a bath of sulfuric acid but I think that is overkill -  just use a bit of vinegar if you have any trouble.

7) The IR filter before and after cleaning, and the print film negative cut to the same size.

Cut out two pieces of the photographic film to the same dimensions of the glass which the IR filter was on. Note that you want processed print film negative which is completely black. It will stop visible light but let IR light through. Mine was pretty much black (it had a brown tint to it). I decided to use two layers a I could still see some light through just one and adding the second layer did not seem to reduce the amount of IR getting through.

8) Remove the IR filter, clean off the IR filtering film, insert the print film and place the cleaned IR filter back on top. You may find that the glass sticks up a bit, don't worry the foam around the CCD will push it down.

Now you just have to reassemble the camera and you are done.

I bought a couple of IR LEDs to use as a light source below are a couple of examples from the irSight camera. Leave a comment if you have a go at this conversion or have any questions.

My eye as seen by the iSight before conversion. Note the screen reflection.

My eye using the iSight after conversion lit by one IR LED. Note how sharp the edge of the pupil is.

A security feature on a $20 bill. Under normal light the white stripe is not visible.