EyeLink II User Manual version 2.12
(07/02/2006)
©
2002-2006 SR Research Ltd.
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experiment. If you can not calibrate with both eyes select the eye to be used by
pressing the “Left” or Right” button in the Eye to Track section of the Camera
Setup screen, or by pressing the 'E' key.
There are several possible calibration types available, each of which serves
different purpose. By default, a nine-point calibration type (“HV9”) is used.
This is good for most of the eyetracking applications. However, if a large
calibration region (greater than ±25º) is involved in an experiment, the “HV13”
calibration type should be used for best calibration accuracy. Press the “Set
Options” button from the Camera Setup screen to display the Set Options
screen. Check to ensure that the following options are selected for practice:
•
Calibration type: 9-point grid
•
Randomize target order: YES
•
Auto-trigger pacing: 1000 msec
Press the “Previous Screen” button when done to return to Camera Setup.
Begin calibration by pressing the ‘Calibrate’ button from the Camera Setup
menu. A calibration target will appear on both the Host PC display and the
Display PC monitor. The subject display is drawn by the TRACK.EXE
application, in response to commands from the EyeLink II system. The Host PC
display will also display the raw pupil position as a moving colored circle, and a
thresholded eye camera image. A status bar at the bottom-right of the display
reports the progress of the calibration.
The pupil-position cursor(s) will jump about when the subject looks about on
the display, and becomes still when properly fixating the calibration target.
Instructing the subject to carefully look at the white spot in the middle of the
black calibration target will help improve fixation stability. Head movements
during calibration should be discouraged: small head movements are corrected,
but large movements will severely degrade calibration accuracy, due to
distortion of the calibration data pattern and range.
If the cursor jumps continuously and rapidly, or disappears intermittently, the
setup for one or both eye has problems. The eye-movement condition is also
visible at the right side of the status bar at the bottom of the operator's display.
When the pupil appears stable to accept the first fixation, press the ‘Accept
Fixation” button or the
↵
(ENTER) key or spacebar keys. The pupil tends to
come to rest gradually and to make small vergence movements at the start of
the fixation, so do not respond too quickly. However, do not wait too long before
accepting the fixation, as subjects soon begin to make involuntary saccades.
