Tobii X1 Light User Manual
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7.3 Appendix C: Glossary
Monocular/
binocular
Monocular data shown is based on data from each eye
individually. Binocular data is the average of the two eyes.
Gaze precision
Describes the spatial angular variation between individual and
consecutive gaze samples. Gaze precision can be measured
under various conditions. Gaze precision is sometimes also
specified as ‘spatial resolution’.
Gaze accuracy
Describes the angular average distance from the actual gaze
point to the one measured by the eye tracker. Gaze accuracy
can be measured under various conditions.
Sampling rate
Number of data samples per second. The Tobii X1 Light Eye
Tracker has a variable data-rate which is typically between 28
and 32 Hz, i.e. typically between 28 to 32 data samples per
second are collected for each eye. .
Total system latency
The duration from mid-point of the eye image exposure, to
when a sample is available via the API on the client computer.
This includes half of the image exposure time, plus image read-
out and transfer time, processing time and time to transfer the
data sample to a client computer.
Time to tracking
recovery for blinks
When a subject blinks, the eye tracker loses the ability to track
eye gaze because the eye is covered by the eye lid. If the
pupil is occluded for only a short period, the system will regain
tracking immediately when the pupil becomes visible again,
but only if the subject has maintained approximately the same
head position during the blink. Data during blinks are only lost
when the pupil is occluded, i.e. during the eye lid movement
itself or when the eye is closed.
Chapter 7
Appendices
