For our work with a wearable eyetracker, we have attached a small laser
pointer to the headband for calibration. A 2D diffraction grating in
front of the laser projects a 3x3 calibration grid onto any surface.
The primary advantage is that the grid moves with the subject's head, so
the calibration can be completed (or checked later) on any plane surface
without the need to restrain the head or rely on the subject not to move
during the calibration). The projected calibration grid also makes it
much easier to specify the calibration points during the target 'sweep'
because the points are fixed wrt the scene camera attached to the
headband.
When we calibrate to a fixed surface (e.g., for seated subjects using
the MHT), the laser makes it easy for Ss to hold the head steady during
calibration by monitoring the position of the projected points (like the
technique described by Steven Rogers in the previous post).
Jeff Pelz
Center for Imaging Science
Rochester Institute of Technology
Rochester, NY USA
Rogers wrote:
>
> With head mounted optics that bounce a small IR beam off of a
> visor and onto the participants eye, we found that we could
> achieve good calibration accuracy by asking participants to simply
> lock the reflection of the beam in the visor onto some small
> unmoving target in the environment (you nearly always have to
> switch off the lab lights to make participants aware of the small red
> dot in their visual field in the first instance).
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