2
Technical Specifications
The characteristics of an eye tracker can be described in terms of gaze accuracy and gaze precision. Accuracy describes the
angular average distance from the actual gaze point to the one measured by the eye tracker. Gaze precision describes the spa-
tial variation between successive samples collected when the subject fixates at a specific point on a stimuli. More information re-
garding the accuracy and precision measurements can be found in
Appendix B Accuracy and Precision Measurements, page 9
in tests reports available on the Tobii Pro web site. A glossary can be found at
.
2.1
Tobii Pro X3–120 Eye Tracker Specifications
Table 2.1 Gaze Accuracy (preliminary)
Gaze accuracy
1
Tobii Pro X3-120 Eye Tracker (firmware version — 1.7.1)
Binocular
Monocular
At ideal conditions
0.4
0.5
At 25° gaze angle
0.6
0.7
At 30° gaze angle
0.6
0.8
At 1 lux
1.0
1.6
At 300 lux
0.4
0.5
At 600 lux
0.5
0.6
At 1000 lux
0.5
0.7
White stimuli background
0.7
0.9
1.
Accuracy under ideal conditions is measured in the center of the head movement box. Data is collected immediately after calibration in a controlled laboratory environment with constant illumi-
nation with stimuli points at gaze angles of
≤
20º.
Table 2.2 Gaze Precision (preliminary)
Gaze precision at ideal conditions
Tobii Pro X3-120
1
Binocular
Monocular
Artificial Eye
N/A
N/A
Human Eye
0.24
0.34
1.
Dynamic illumination pattern compensation is applied in the Tobii Pro X3–120 Eye Tracker.
Table 2.3 Eye Tracking Specifications (preliminary)
Eye Tracking Specifications
Tobii Pro X3-120 Eye Tracker
Sampling rate
120 Hz
Eye tracking technique
Corneal reflection, dark and bright pupil combination
Binocular tracking
Yes
Pupil measurement
Yes (40 Hz, bright pupil mode only)
Total system latency
<11 ms
Time to tracking recovery
For blinks: immediate
After lost tracking: <100 ms
Head movement
1
Freedom of head movement at 80
cm (width x height)
50 cm x 40 cm (19.7
″
x 15.7
″
)
Operating distance (eye tracker to
participant)
50 – 90 cm (19.6
″
– 35.4
″
)
2
Tobii Pro X3–120 Eye Tracker Product Description v.1.0.2 - en-US
Summary of Contents for X3-120
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