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Friday, June 10, 2005

Machine vision: motion tracking

[Audio Version]

Following is another in my series of ad hoc journal entries I've been keeping of my thoughts on machine vision.

I was thinking earlier about something related to the head tilting issue. As I was walking around, I tracked stationary points in space. While my sense is of a stable view of the stationary point, I found that my eyes do actually saccade very rapidly and very subtly to keep the target in the center of my fovea. That is, my gaze is not stable.

My gaze does appear to be predictive, though. It seems as I move, my eye comes to predict where the stationary point will be in the next moment and keeps my eyes moving to keep up. It's a little like shooting skeet. You see the clay pigeon emerge from the launcher and continuously adjust your muscles to keep it in your gun's sights. You could close your eyes and keep moving the gun along the predicted trajectory, but as time goes by, the gun will move farther and farther off target.

As a side note, this may help explain why my eyes sometimes get tired when I rock in my seat while working at my computer. The screen's position relative to my eyes is constantly changing. Surely my eyes have to work harder to keep focused on the screen's contents.

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