EyeLink 1000/2k and
EyeLink Remote
Introduction and Training
Session
SR Research Ltd.
Toronto - Ottawa, Canada
Agenda
• Functional system overview
• System architecture
• Eye tracking experiment process
• EyeLink recording data / Data Viewer
• Analog card
• EyeLink support
EyeLink CL Overview
• Focal Imaging Technology
– Large camera field of view
– High resolution eye data
• EyeLink CL hardware
– EyeLink CL High Speed
Infrared Camera
– IR illuminator
– CameraLink cable
– Custom High Speed Image
Processing Board
EyeLink CL Overview
• Extendable Hardware Platform
–
–
–
–
EyeLink
EyeLink
EyeLink
EyeLink
Tower
Desktop
Primate
Remote
• Complete Software Package
– Host Eye Tracker Application
– Application Programming Interface
EyeLink Tower and Desktop
• Fastest Sampling Rate:
– 2000 / 1000 / 500 / 250 Hz recording
• High Resolution:
– 0.01 ° RMS in pupil-CR 1000 Hz tracking mode
• Accurate:
– Drift free, down to 0.15° average accuracy (0.25 - 0.5°
typical)
• Real-time:
– Access eye position data with < 2-ms delay
EyeLink Tower and Desktop
• Easy:
– Fast and simple setup, calibration and validation
• Comfortable:
– Head-supported design
• Real-time operator feedback
• Compatible:
– With EyeLink I and II display software
– Works with E-Prime, Presentation, and other 3rd party
experiment software
EyeLink Tower and Desktop
EyeLink Tower and Desktop
EyeLink Tower and Desktop
• Tower Mount:
– Larger tracking range: (55 horizontal, 45 vertically vs.
32 horizontal, 25 vertical)
– Minimal adjustments
•
Desktop Mount:
–
–
–
–
Supports monocular and binocular tracking
Compact, mirror-less mount and more portable
More compatible with glasses
More portable.
System Architecture
System Architecture
Host Application
• Controls the eye tracker
•Performs image analysis
•Performs data recording
•Performs eye event parsing
•Configures preferences
• Provides real-time feedback
•Gaze view: Gaze cursor on background image
•Plot view: Eye traces over time
• Controls other optional setups
•Analog output board
•Gaze video overlay system
System Architecture
Display PC Software
• Allow full experiment control
•Integrates calibration and gaze position collection into one
step
•Sets any tracker preference
•Sends commands to control tracker
• Time stamps experiment events with messages
• Real-time access to eye sample and eye event data structures
• Allows the users to focus on stimulus presentation and data
analysis
Eye Tracking
Experiment Process
•Pre-Experiment activities
•Check Tracker Settings (Set Options Screen)
•Participant setup
•Calibration
•Validation
•Running the experiment
•Blocks
•Trials
•Optional drift correction/drift checking
•Recording and data acquisition
•Data analysis
Participant Setup
Camera Setup Screen
Participant Setup
Mirrored Mount
The participant setup becomes a smooth and fast
procedure with practise. Try to follow the steps below:
1) Set the height of the monitor and height of the tower mount
2) Set the eye-selection knob to track the intended eye
3) Set the mirror at the intended angle
4) Adjust the chair height as well as the chinrest position
5) Find the pupil by clicking on the eye image
6) Focus the eye camera
7) Adjust the thresholding level for pupil and CR
8) Check the setup by asking the subject to look at four corners
9) Calibration, validation and recording
Participant Setup
Desktop Mount
The participant setup becomes a smooth and fast
procedure with practise. Try to follow the steps below:
1) Place the monitor at the intended distance and height
2) Set up the desktop optics; check out the height of the mount
3) Adjust the chair height as well as the chinrest position
4) Adjust the camera angle and position
5) Find the pupil by clicking on the eye image
6) Focus the eye camera
7) Adjust the thresholding level for pupil and CR
8) Check the setup by asking the subject to look at four corners
9) Calibration, validation and recording
Participant Setup
Optimal Eye Position
•Adjust the height of the chair so that the
subject is comfortable and his/her eye line is
aligned to upper part of the monitor.
•The position of the forehead rest should be just
above the eye brow. The figures on the right
shows that the subject is seated too high (topright) or too low (bottom-right).
Participant Setup
Search Limits: when to use and how to enable
• The Search Limits box (red box) can be used to
reduce the area of the full camera image that is
searched to find the eye.
• Normally the search limits box is not needed,
however with some participants glasses it can be
used to exclude other regions of the camera
image that may otherwise be detected as a pupil
/ CR reflection pattern.
• The disadvantage of the search limit is that if the
participant completely removes their head from
the head support and then puts it back in the
head support device the search limits box may
not be in the correct location to track the eye.
Participant Setup
Adjusting Search Limits
• Press “Use Search Limits” to
toggle on /off search limits.
• Use ALT and cursor keys to
adjust the shape of the
search limits.
• Use SHIFT and cursor keys
to adjust the position of the
search limits.
Participant Setup
Centroid Vs. Ellipse
Pupil Tracking Modes
• The Centroid mode tracks the
centre of the thresholded pupil
using a centre of mass algorithm.
• The Ellipse mode determines the
centre of the pupil by fitting an
ellipse to the thresholded pupil mass.
• This modes advantage is that it
has very low noise.
• The advantage of this mode is
decreased drift potential. It can cope
well with pupil occlusion.
• The disadvantage of this mode is
eye position can drift if there is
significant occlusion of the pupil
(for example by eyelids).
• The disadvantage is that it has a
higher noise level.
Participant Setup
Focusing the Eye Camera
Focusing Arm
Focused
Not Focused
Participant Setup
Setting Pupil Threshold
Figure 1
The pupil threshold can be adjusted
automatically, through the Auto-threshold
command, or manually, through the
up/down arrow. A threshold too low will
result in shadows (figure.1), while a
threshold too high will result in a noisy
signal (figure. 2).
Figure 2
Participant Setup
Symptoms of Poor Pupil Threshold
Pupil clipped and lost
Good
Corner Shadow captures pupil
Participant Setup
Setting Corneal Reflection (CR)
Good Corneal Reflection
Poor Corneal Reflection
Participant Setup
Binocular vs. Monocular Mount
Participant
ParticipantSetup
Setup
Subjects wearing glasses
Binocular Setup
Good mirror angle
Poor mirror angle
Participant Setup
Participants with glasses
Status Panel
Monitor the status of camera image of the tracked eye
throughout setup, calibration, validation and recording phases.
Pupil
OK (green): Pupil present and can be tracked at selected
sample rate
SIZE (yellow): Occurs when the pupil size is larger than the
maximum allowed pupil size
MISSING (red): Pupil not present
Corneal (only operational in Pupil-CR mode)
OK (green): Corneal reflection is present and can be
tracked
MISSING (red): Corneal reflection is not present
Calibration
Mapping raw eye data to either gaze position or HREF coordinate
Calibration
Always checks for the calibration grid at the end of calibration.
Good Calibration
Poor Calibration
Calibration
Improving calibration accuracy:
• Always ask the subject to look at the four corners of the
display after performing the camera setup. Watch for the
pupil or CR warning signals on the tracker screen due to
pupil occlusion or improper thresholding.
•Ensure that the threshold pupil area be inside the pupil box when
the subject is looking at any area of the display.
•The corneal reflection should never be lost or misidentified when
the subject looks around the calibrated area.
Calibration
Improving calibration accuracy (continued):
• Encourage the subjects to sit still!
• Subjects who have never been calibrated before require
some practice in stably fixating the calibration targets. Try
to perform at least two calibrations per subject before
beginning to collect data.
• Try to match the background color of the screen during
calibration and validation to that of the test displays.
Changes in pupil size caused by large brightness differences
will reduce recording accuracy.
Validation
Checking gaze accuracy of the calibration
Validation
Validation Results:
• GOOD (green background): Errors are acceptable.
• FAIR (grey background): Errors are moderate, calibration
should be improved.
• POOR: (red background): Errors are too high for useful
eye tracking.
In general, ensure that the average gaze error is within 0.5
and maximum error within 1.0
Recording
Gaze View
Recording
Plot View
EyeLink Remote
• Accurate:
– 0.5° average accuracy
• Fastest Remote Sampling Rate:
– 500 Hz monocular eye tracking
• Real-time:
– Access eye position data with 3.0 msec delay
• Head Free:
– 22 x 18 x 20 cm (horizontal x vertical x depth) allowable
head movement at a 60 cm camera distance
EyeLink Remote
• Reliable Head Distance Tracking:
– Maximum head movement speed of 100 cm / second,
even during blinks
• Robust Blink Recovery:
– Recovery time of 2 msec
• Online Saccade Detection:
– Reliably monitor both fixation and saccade events of as
low as one degree
• Dual Purpose Eye Tracker:
– Quickly switch between the EyeLink Desktop and EyeLink
Remote systems.
EyeLink Remote
EyeLink Remote
EyeLink Remote
The participant setup becomes a smooth and fast
procedure with practise. Try to follow the steps below:
1) Use proper lens; set the ELCL configuration to “Remote (Level)”;
2) Set the height of the monitor; eye-screen distance at about 70 cm
3) Place the camera right in front of the monitor
4) Raised the desktop mount to maximize tracking range.
5) Seat the subject and place the target sticker
6) Find the pupil by clicking on the eye image
7) Adjust the thresholding bias for pupil and CR
8) Check the setup by asking the subject to look at four corners
9) Calibration, validation and recording
EyeLink Remote
•Place the target sticker on the
subject’s forehead, just above the
eyebrow of the tracked eye
•The eye and the sticker stay within
the camera image when the subject’s
head moves
•An ideal target-camera distance
should be about 550 mm to 600 mm
EyeLink Remote
Target is too close to the eye vertically
Target has a large angle
EyeLink Remote
Pupil threshold bias adjusted by UP or DOWN cursor keys (1.08 typical)
CR threshold bias adjusted by – or + keys (1.00 typical) .
EyeLink Remote
• Monitor the thumbnail camera images at the lower left
corner of the tracker screen
• The two dots in the middle panel reflect the target and eye
position in the global camera image
• For reliable tracking, both dots should stay within the red
box.
EyeLink Remote
Pupil
OK:
SIZE:
Pupil present and can be tracked at selected sample rate
Occurs when the pupil size is larger than the maximum allowed pupil
size or smaller than the required size (e.g., too bright or small pupil)
MISSING: Pupil not present
Status Panel
Corneal
OK:
Corneal reflection is present and can be tracked
MISSING: Corneal reflection is not present
Target
OK:
Target is present and can be tracked
MISSING: Target is not present.
EYEDIST: Target is placed too close to the eye on the vertical dimension.
ANGLE: Target has too large an angle to be recognized properly.
Tracker Settings
Link/Analog Filter
EyeLink Recording Data
•EDF File (binary File)
•Use EDF2ASC converter to get ASC files
•Use EyeLink Data Viewer for direct analysis
•What’s recorded?
•Samples
•Events
•Saccades
•Fixations
•Blinks
•Messages
•Buttons
(Please read Chapter 4 of EyeLink 1000 User Manual)
EyeLink Recording Data
•Samples
• System time, x, y and pupil size
• With optional velocity, resolution, and CR status
6079861
6079862
6079863
6079864
6079865
6079866
6079867
6079868
6079869
6079870
503.7
503.7
503.8
503.8
503.9
503.7
503.7
503.6
503.6
503.7
680.3
680.1
680.1
680.2
680.2
680.1
680.1
680.0
680.1
680.2
972.0
972.0
972.0
972.0
971.0
971.0
971.0
970.0
970.0
970.0
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
(Please read Chapter 4 of EyeLink 1000 User Manual)
EyeLink Recording Data
•Saccades
• SSACC: eye, start time
• ESACC: eye, start time, end time, duration, start x/y,
end x/y, amplitude, peak velocity.
SSACC L
ESACC L
…
SSACC L
ESACC L
6079955
6079955 6079962
8 507.5 682.5 511.9 682.0 0.20
38
6080723
6080723 6080763 41 513.8 679.7 633.5 550.5 7.94 285
(Please read Chapter 4 of EyeLink 1000 User Manual)
EyeLink Recording Data
•Fixations
• SFIX: eye, start time
• EFIX: eye, start time, end time, duration, average x/y,
pupil size, and additionally, resolution.
SFIX
EFIX
...
SFIX
EFIX
L 1454748
L 1454748
1454907
160
510.3
4.1
1187
28.45
27.50
L 1454919
L 1454919
1455873
955
514.0
0.3
1361
28.40
27.50
(Please read Chapter 4 of EyeLink 1000 User Manual)
EyeLink Data Viewer
EyeLink Data Viewer
•Excellent Data Visualization
•Spatial Overlay, Temporal Graph, and Playback Views
•Flexible Event Filtering
•Fixations, Saccades, Blinks, Interest Areas, etc.
•Reaction Time Definition, Interest Period Definitions
•Detailed Output Reports
•Fixation, Saccade, Interest Area, Trial, Message, or Sample Reports
•Full Experiment Integration by Messages
•Images, Interest Areas, and Trial Condition Variables
EyeLink Data Viewer
Generates detailed Fixation, Saccade, Interest Area and Trial reports
Analog Card
Analog Card
Analog Card
• Real-time analog output of x, y position and pupil
size data
• Supports analog output and digital input and output
- Digital inputs can be configured to record external
synchronization messages to the eye tracker
- Digital outputs can be set up to send synchronization
signal to external systems
• Ideal in providing real-time data access to any thirdparty analysis systems that cannot run Experiment
Builder and other EyeLink programming API
EyeLink Support
• Documents
•EyeLink 1000 User Manual
•EyeLink 1000 Installation Guide
•SR Research Experiment Builder
•Windows Programmers Guide
•EyeLink Data Viewer
• Contact Information
•E-mail: support@sr-research.com
•Phone: 1-613-826-2958/ 1-866-821-0731
•Web: http://www.sr-support.com
EyeLink Support
We will take a short break. Then
it’s your turn to get eyetracking!