eye link ii system introduction and basic training session

Copyright of SR Research Ltd., 2001 - 2002

EyeLink IITraining Session

Eye Link II System Eye Link II System Introduction and Basic Introduction and Basic

Training SessionTraining Session

SR Research Ltd.

Mississauga - Ottawa, Canada


EyeLink IITraining SessionAgendaAgenda

Functional System Overview System Architecture Eye Tracking Experiment Process Software Architecture EyeLink EDF Data/Data Viewer EyeLink Gaze Overlay EyeLink Support



•Binocular / Monocular•250 / 500Hz•Corneal Reflection vs. Pupil Only•Head tracking / Head-free Recording•Real-time Data Access•Windows API and Experiment Builder

Functional System overview



EyeLink IIEyeLink IIHigh Speed Eye Tracking High Speed Eye Tracking

SystemSystemEyeLink II Key Features

• High Speed – Binocular Recording at sampling rate of 250 or 500Hz.

• Exceptional Resolution <0.01°, and low noise <0.01° RMS.

• Accurate - Average gaze position error <0.5°. • 2 Modes of Operation - Pupil-Only or Pupil-

Corneal. • Headband assembly is lightweight robust and

ergonomic. • Compatible with most eyeglasses and contact

lenses.• Easy Set-up, Calibration, and Validation.• Real-time operator feedback. • Online analysis of data into saccades, fixations,

and blinks. • Powerful Application Programming Interface

(API). • Compatible with EyeLink I applications.



System System architecture Host PC Data flow / integration Display PC


EyeLink IITraining SessionHost ApplicationHost Application

Runs on ROM DOS environment

Performs image analysis, eye event parsing, and data recording functions

Allows the system operator to view real-time gaze position overlaid on a static display representation while data recording is being performed

Allows preference selection, camera setup, calibration, and recording functions

Facilitates for the selection of 5 different calibration types (3pt - 13pt)


EyeLink IITraining SessionDisplay APIDisplay API

Integrates calibration, gaze position collection, head position compensation, and saccade and fixation analysis into one step

Gaze position is overlaid on experiment graphics in real time, allowing validation of calibration accuracy before recording and monitoring of data quality during data collection

Perform drift correction at any time

Time stamped experiment event messaging; Dedicated Ethernet connection between Host and Display so no data is lost

Allows the user to focus on stimulus presentation and data analysis



•Pre-Experiment activities•Participant setup•Calibration•Validation

•Running the experiment•Drift correction•Trials•Blocks

•Recording and Data Acquisition•Data analysis

Eye Tracking experiment process



Pre-Experimental Pre-Experimental ActivitiesActivities

EyeLink II is provided with several system configuration (.ini) files, which are designed to help the Experimenter control the tracker.

Before starting recording eye movements, it is critical to properly set-up the eyes and head cameras, and to calibrated/validate the subject.

A poor system set-up will result in a low data accuracy.

One of the most useful screens is called Set Options. Often it is overlooked.



Pre-Experimental Pre-Experimental ActivitiesActivities



Participant Setup Participant Setup - Headband- Headband

The Headband placement becomes a smooth and fast procedure with practise: learn on yourself and test on colleagues before running an experiment. It should take less than 2 days of practise.



Participant SetupParticipant Setup- Eye Cameras- Eye Cameras



Participant Setup Participant Setup - Head Camera- Head Camera

Please, adjust the monitor or participants height till you reach this result



Optimal

Too Far Too Close

Camera too High Camera too Low

Pupil too High Pupil too Low

Participant Setup Participant Setup - Optimal Eye View- Optimal Eye View



Participant Setup Participant Setup - Eye in Focus- Eye in Focus

Not focused Focused



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 (fig.1), while a threshold too high will result in a noisy signal

(fig. 2).

Fig. 1

Fig. 2

Participant Setup Participant Setup - Eye Threshold- Eye Threshold



Calibration

Experiment Setup



Experiment Setup

Calibration

Good

poor



Experiment Setup

Validation



Experiment Setup

Validation

Good Poor



Trials: •Smallest unit or presentation of a display•Try to perform a drift correction for each trial

Blocks: •Many trials make up a block.•Try to arrange a short break between blocks and check whether re-calibration is necessary.

Data Recording

Data Analysis – Selective filtering based on application

Running Experiment



Running Experiment

Drift correction



Running Experiment

Avoiding Large Drifts

•Headband slippage•Make sure that headband is not placed too far forward•Suspend the cable from above the subject or clip it to the back of the subject's collar

•Head or Body Movements•Sit still and avoid major head/body movements•Use chin-rest•Supply a comfortable, stable chair

•Pupil Occlusion•Check the positions and alignments of the camera and subjects' eye positions



EyeLink Recording Data

•EDF File•Use EDF2ASC converter to get ASC file•Use EyeLink Data Viewer for analysis

•What’s recorded?•Samples•Events

•Messages•Buttons•Saccades•Fixations•Blinks



MSG 62792716 TRIALID PIX1 Normal

START 62797388 RIGHT EVENTS

PUPIL AREA

EVENTS GAZE RIGHT TRACKING P FILTER 2

SFIX R 62797396

MSG 62797517 3 DISPLAY ON

MSG 62797517 SYNCTIME 3

BUTTON 62797525 5 0

EFIX R 62797392 62797858 470 510.5 382.8 1813

SSACC R 62797860

ESACC R 62797860 62797914 58 503.6 385.5 429.2 128.3 7.97 194.9

SFIX R 62817356

MSG 62817515 TIMEOUT

EFIX R 62817356 62817614 262 760.0 19.1 1465

END 62817622 EVENT RES 35.57 36.17

MSG 62817636 TRIAL_RESULT 0

MSG 62817636 TRIAL OK

EyeLink Recording DataASC File structure




63636348 511.1 383.3 1215.0 513.4 385.9 1622.0 .....

63636352 510.8 382.6 1216.0 513.4 385.9 1623.0 .....

63636356 510.0 382.5 1218.0 513.5 386.1 1624.0 .....

63636360 510.0 382.3 1219.0 513.4 386.3 1625.0 .....

63636364 510.1 382.1 1220.0 513.4 385.8 1626.0 .....

63636368 510.3 382.3 1220.0 513.4 385.8 1627.0 .....

63636372 510.4 382.4 1221.0 513.5 385.9 1631.0 .....

63636376 510.6 382.6 1221.0 513.8 386.2 1630.0 .....

63636380 510.9 382.6 1221.0 514.0 386.2 1629.0 .....

(Please read chapter 4 of the user manual)

Samples:

•System time, x, y and pupil size

•With additional velocity, resolution, and CR status




Saccades:

•SSACC: eye, start time

•ESACC: eye, start and end times, duration, start x/y, end x/y, saccade size, and additionally peak velocity, resolution

SSACC L 63644396

SSACC R 63644396

ESACC L 63644396 63644424 32 646.9 219.5 853.9 194.8 6.16 394.8

ESACC R 63644396 63644424 32 659.3 212.7 859.6 191.9 5.96 385.6





Fixations:

•SFIX: eye, start time

•EFIX: eye, start and end times, duration, average x/y, pupil size, and additionally, resolution

SFIX L 63644800

SFIX R 63644800

EFIX R 63644800 63645136 340 150.7 277.4 1853

EFIX L 63644800 63645136 340 134.3 277.7 1518



EyeLink IITraining SessionData ViewerData Viewer



Three different viewing modes Spatial, Temporal and Gaze Cursor Playback

Output detailed reports Fixation, Saccade, Interest Area, or Trial

Export Data Views as JPG images Import multiple recording files into one viewing

session Supports EyeLink I, II, 1000/2k, and Remote EDF

files Fully integrated with API



Generate detailed Fixation, Saccade, Interest Area and Trial reports for further analysis



Create ‘Interest Periods’ to analyze data within a specified period of time

Define ‘Reaction Time Definitions’ for automatic trial by trial reaction time calculation

Monitoring eye data over time



For more detailed information on our products and services, visit our website onwww.sr-research.com

orwww.sr-support.com

Send us an email [email protected]

or call toll free1-866-821-0731(North America Only)

EyeLink Support


EyeLink IITraining SessionEyeLink Support



We will take a We will take a short break. short break.

Then it’s your Then it’s your turn to get turn to get

eyetracking!eyetracking!

eye link ii system introduction and basic training session

Documents