Tobii X2-30 Eye Tracker Compact Edition Product Description page 15

Appendix A: Glossary
M M o o n n o o c c u u l l a a r r / / b b i i n n o o c c u u l l a a r r Monocular data shown is based on data from each eye individually. Binocular data is the average of
the two eyes.
G G a a z z e e p p r r e e c c i i s s i i o o n n Describes the spatial angular variation between a set of consecutive gaze samples. Gaze precision
can be measured under various conditions. For more details, see Appendix B: Accuracy and
Precision Measurements .
G G a a z z e e a a c c c c u u r r a a c c y y 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. For more details, see Appendix
B: Accuracy and Precision Measurements .
S S a a m m p p l l i i n n g g r r a a t t e e Number of eye tracking data samples per second.
T T o o t t a a l l s s y y s s t t e e m m l l a a t t e e n n c c y y 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.
T T i i m m e e t t o o t t r r a a c c k k i i n n g g When a subject blinks, the eye tracker loses the ability to track eye gaze because the eye is covered
r r e e c c o o v v e e r r y y f f o o r r b b l l i i n n k k s s 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.
T T i i m m e e t t o o t t r r a a c c k k i i n n g g An eye tracker working in a natural user environment may occasionally lose track of the subject's
r r e e c c o o v v e e r r y y a a f f t t e e r r l l o o s s t t eyes, e.g., when the subject completely turns away from the tracker. If a period of a few hundred
t t r r a a c c k k i i n n g g milliseconds elapses during which the eye tracker is unable to detect the eyes in close proximity to
where they were last detected, the eye tracker will start searching for the eyes within the entire head
movement box. The stated measurement is the typical time to tracking recovery in such a situation. If
the eye tracker is unable to detect the eyes of the subject even after about one minute, the system
will enter a "slow search" mode, leading to larger recovery times.
F F r r e e e e d d o o m m o o f f h h e e a a d d
Describes an area ( width x height in cm) where at least one eye is within the eye tracker's field of
m m o o v v e e m m e e n n t t
view.
O O p p e e r r a a t t i i n n g g d d i i s s t t a a n n c c e e
Describes the range of distances (minimum and maximum) between the subject's eyes and the
surface covering the eye tracker sensors at which eye tracking can be done while maintaining
tracking.
E E y y e e t t r r a a c c k k i i n n g g
Gaze data calculations are performed by firmware embedded in the eye tracker or in a separate
p p r r o o c c e e s s s s i i n n g g u u n n i i t t processing unit.
Product Description v.1.0 - en-US
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A: Glossary