Optics: Eyesight direction sensor

Colleagues,

My friend was bragging about his Canon camera, and he mentioned that it
can focus in the direction of the eyesight. From the user perspective
it looks like this:

* Camera sight has a crosshair that consists of 7 dots. 1 in the
center. 4 evenly spaced on the horizontal line. 2 evenly spaced on the
vertical line.
* Photographer looks through, and as he changes his
sight direction (i.e. rotates his eyeball), one of the 7 dots lights up
and camera re-focuses in the direction of that dot.

How does the camera sense the direction of eyesight?

There could be many uses for such sensor.

Best,
Nick

I think using CCD cameras. Equivalent to that of an optical mouse.

I just did a simple experiment. I took my optical mouse, stuck my eye into it (with the LED still on) and rolled the eye in different directions. The cursor on the screen didn?t move. But that doesn?t mean that the approach that you have mentioned can?t work. It, probably, requires different lens and/or better CCD resolution.