Wednesday, May 14, 2008

Modify you webcam to capture infrared light

Found this a while back, might be useful if building a home-brew webcam eye tracker..
The most common method of eye tracking today is to use IR light to create corneal reflections. To do this you need a pair of IR LED´s (perhaps a couple of these) and a camera that is capable of receiving that spectrum of light. More or less all cameras can do this but manufacturers usually place a filter in front of the sensor so that it only picks up the perceivable spectrum of light. By removing this and replacing it with a filter that only passes IR you get a camera suitable for corneal reflection based eye tracking.

Next step would probably be to locate the head and the eyes in the video sequence. A good starting point for this is the OpenCV library. Martin Wimmer has created the EyeFinder system which locates head and eyes in real-time. Upon locating the eyes an area is defined as a region of interest which is passed on to image processing algorithms. These will typically locates the pupil by ellipse fitting and the glints/reflections that the IR lights create and somewhere along those lines it becomes "easier said than done" =) (I have yet to try building my own =)

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