EyeTracking - Meg Wiki

Revision 4 as of 2009-04-23 12:53:14

Clear message
location: EyeTracking

Eye tracking

The CBU currently has 4 eye trackers. One is in the MEG lab, one in the MRI (from May 2009), and we have two separate eye trackers for use in other locations. All eye trackers are from SMI and use the same software for controlling the eye tracking hardware, for stimulus presentation and for analysis of the eye tracking data.

All 4 eye trackers use 'dark pupil' technology, where the gaze of the eye is tracked by identifying the pupil and the reflection of an infra-red light source on the cornea.

Eye trackers come in two variaties: 'contact' and 'remote'. With contact eye trackers the camera and light source are fixed to the head, or the head is on a chin rest to limit movements relative to the camera. In remote systems the camera and light are in a fixed location, at some distance from the subject, enabling some head movements. Contact systems are more precise and reliable, in general.

Another important feature of an eye tracker is the frequency. To be able to follow the eye during saccades the minimum frequency is about 200 Hz.

MEG eye tracker

This is a 50 Hz system that should theoretically be called a remote eye tracker, but actually behaves more like a contact system as head movement is extremely limited in the MEG helmet. For that reason the camera can actually be zoomed in quite closely and the accuracy of the MEG eye tracker should be reasonably high.

MRI eye tracker

The MRI eye tracker will arrive in May. It will be a system comparable to that in the MEG.

RED eye tracker

RED stands for 'Remote Eye-tracking Device', and this is a remote system.

Hi-speed eye tracker

This is a contact system that will allow frequencies of up to 1250 Hz for monoculair eye tracking and 500 Hz for binoculair tracking.