EyeLink II User manual

EyeLink
®
II Head Fixed Eye Tracker
User Manual
Version 2.12
Copyright ©1997-2006, SR Research Ltd.
EyeLink is a registered trademark of SR Research Ltd, Mississauga, Canada.

EyeLink II User Manual (07/02/2006) ©2002-2006 SR Research Ltd. 2
Table of Contents
1. Introduction ........................................................................................................... 1
1.1 Supporting Documents......................................................................... 1
1.2 EyeLink®II System Overview ................................................................ 2
1.3 EyeLink II System Configuration .......................................................... 2
1.3.1 EyeLink II Host PC ........................................................................................ 3
1.3.2 EyeLink II Display PC.................................................................................... 3
1.3.3 EyeLink II PCI Card....................................................................................... 5
1.4 System Specifications........................................................................... 5
1.4.1 Tracking Modes ............................................................................................. 5
1.4.2 Operational / Functional Specifications ......................................................... 5
1.4.3 Physical Specifications.................................................................................. 6
2. EyeLink II Tracker Application Operation ........................................................... 8
2.1 Starting the Host Tracker ..................................................................... 8
2.2 Modes of Operation .............................................................................. 8
2.3 EyeLink II Tracker Application Navigation............................................. 9
2.3.1 Offline Screen.............................................................................................. 10
2.3.2 Camera Setup Screen ................................................................................. 12
2.3.3 Set Options Screen ..................................................................................... 16
2.3.4 Calibration Screen ....................................................................................... 21
2.3.5 Validation Screen ........................................................................................ 23
2.3.6 Drift Correct Screen..................................................................................... 25
2.3.7 Output Screen ............................................................................................. 27
2.3.8 Record Screen............................................................................................. 29
2.4 Status Panel....................................................................................... 31
2.5 Mouse Simulation Mode ..................................................................... 32
2.6 Configuration Files and Experiment Directories .................................. 32
2.7 Analog Data Types.............................................................................. 33
3. An EyeLink II Tutorial: Running an Experiment ............................................... 35
3.1 The Camera Setup Screen .................................................................. 36
3.2 Adjusting Eye Camera Position ........................................................... 37
3.3 Setting Pupil Threshold ...................................................................... 40

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3.4 Calibration......................................................................................... 42
3.5 Validation .......................................................................................... 47
3.6 Recording Gaze Position ..................................................................... 49
3.7 Drift Correction .................................................................................. 49
3.8 Exiting EyeLink II............................................................................... 51
3.9 EyeLink II Setup Summary................................................................. 51
3.10 Experiment Practice ........................................................................ 52
3.11 Next Steps: Other Sample Experiments............................................ 52
4. Data Files ............................................................................................................. 56
4.1 File Contents...................................................................................... 56
4.2 Recording EDF Files........................................................................... 57
4.2.1 Recording from the EyeLink II Host PC....................................................... 57
4.2.2 Recording from the EyeLink API ................................................................. 57
4.3 The EyeLink On-Line Parser ............................................................... 57
4.3.1 Parser Operation ......................................................................................... 57
4.3.2 Parser Limitations........................................................................................ 58
4.3.3 EyeLink Parser Configuration...................................................................... 58
4.3.4 Parser Data Type ........................................................................................ 59
4.3.5 Saccadic Thresholds ................................................................................... 59
4.3.6 Pursuit Thresholds ...................................................................................... 60
4.3.7 Fixation Updates ......................................................................................... 60
4.3.8 Other Parameters ........................................................................................ 61
4.3.9 Sample Configurations ................................................................................ 61
4.4 File Data Types .................................................................................. 62
4.4.1 Samples....................................................................................................... 62
4.4.2 Position Data ............................................................................................... 63
4.4.3 Pupil Size Data............................................................................................ 66
4.4.4 Button Data.................................................................................................. 66
4.5 Events ............................................................................................... 66
4.5.1 Messages .................................................................................................... 67
4.5.2 Buttons ........................................................................................................ 67
4.5.3 Eye Movement Events................................................................................. 67
4.6 Setting File Contents .......................................................................... 71
4.6.1 Sample Data................................................................................................ 72

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4.6.2 Event Data................................................................................................... 72
4.6.3 Event Types ................................................................................................ 73
4.7 EDF File Utilities ................................................................................ 73
4.7.1 EDFSCAN ................................................................................................... 74
4.8 Using ASC Files.................................................................................. 74
4.8.1 EDF2ASC .................................................................................................... 75
4.8.2 Translator Options ....................................................................................... 75
4.9 The ASC File Format .......................................................................... 78
4.9.1 ASC File Structure....................................................................................... 78
4.9.2 Sample Line Format .................................................................................... 79
4.9.3 Event Line Formats ..................................................................................... 82
4.9.4 Data-Specification Lines.............................................................................. 84
4.10 Processing ASC Files ....................................................................... 86
4.11 An ASC File Processing Program ...................................................... 86
5. Troubleshooting .................................................................................................. 88
Problem: Eye Camera Images are blank or blue.......................................... 88
Problem: LED Warning on Host PC startup ................................................. 88
Problem: Host PC Warning Message or Image Loss ...................................... 88
6. System Care......................................................................................................... 90
6.1 Maintenance ...................................................................................... 90
6.2 Storage and Transportation ................................................................ 91
7. Important Information ......................................................................................... 93
7.1 Safety ................................................................................................ 93
7.1.1 Electrical Isolation Safety ............................................................................ 93
7.1.2 Eye Illumination Safety................................................................................ 93
7.2 Limited Hardware Warranty ............................................................... 94
7.3 Limited Software Warranty ................................................................. 95
7.4 Copyrights / Trademarks ................................................................... 95
8. Appendix A: Using the EyeLink II Analog and Digital Output Card................ 96
8.1 Analog Data Quality ........................................................................... 96
8.2 Setting up the EyeLink II Analog Card ................................................ 97
8.2.1 Installing Analog Output Hardware.............................................................. 97
8.2.2 Connections to Analog Card........................................................................ 97
8.2.3 Noise and Filtering ...................................................................................... 97

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8.3 Digital Inputs and Outputs................................................................. 97
8.3.1 Analog Data Output Assignments ............................................................... 98
8.3.2 Analog Data Types and Ranges.................................................................. 99
8.3.3 Scaling of Analog Position Data .................................................................. 99
8.4 Pupil Size Data................................................................................. 100
8.5 Time base and Data Strobe............................................................... 100
8.5.1 Strobe Data Input ...................................................................................... 101
8.5.2 Over sampling and Toggle Strobe............................................................. 101

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List of Figures
Figure 1-1: Typical EyeLink II System Configuration ........................................ 2
Figure 2-1: Screen Overview of EyeLink II Tracker Program............................. 9
Figure 2-2: EyeLinkII Offline Screen............................................................... 10
Figure 2-3: EyeLink II Camera Setup Screen .................................................. 12
Figure 2-4: EyeLinkII Set Option Screen ....................................................... 16
Figure 2-5: EyeLink II Calibration Screen....................................................... 21
Figure 2-6: EyeLinkII Validation Screen ......................................................... 23
Figure 2-7: EyeLinkII Drift Correction Screen................................................. 25
Figure 2-8: EyeLinkII Output Screen.............................................................. 27
Figure 2-9: EyeLinkII Record Screen .............................................................. 29
Figure 2-10 EyeLink II Status Panel............................................................... 31
Figure 3-1: Example Camera Setup Screen before Camera Setup. .................. 36
Figure 3-2: Size and Vertical Eye Camera Adjustments ................................. 38
Figure 3-3: Horizontal Adjustments of Eye Camera ....................................... 39
Figure 3-4: Focusing the Eye Camera ........................................................... 40
Figure 3-5: Symptoms of Poor Pupil Threshold.............................................. 41
Figure 3-6: Corner Effects Seen with Head Rotation ...................................... 42
Figure 3-7. Calibration Grid following a Good and Poor Calibration ................ 45
Figure 3-8. Performing an online drift correction with mouse click ................. 51

EyeLink II User Manual (07/02/2006) ©2002-2006 SR Research Ltd. 7
Read instructions before use.
Type BF equipment (applied parts):
Metal parts connected to chassis of computer may
contact user. Compliance with 601-1 medical
equipment standards requires use of a medical grade
power supply.
Entela Safety Mark: Compliance of this product with
UL 2601-1, CSA C22.2 N0.601.1 and IEC 60601-1 is
certified by Entela, an independent testing body.
CONTACT ADDRESS
SR Research Ltd.
5516 Main St., Osgoode, Ontario, Canada K0A 2W0
Fax: [phone]
Phone: [phone]
Toll Free Phone: [phone] (North America Only)
http://www.eyelinkinfo.com/

EyeLink II User Manual version 2.12 (07/02/2006) ©2002-2006 SR Research Ltd.
1
1. Introduction
This section introduces the EyeLink II system, technical capabilities, and
supporting documentation.
IMPORTANT: Be sure you have read and agree to the end user license
agreement provided in section 7.2 of this document before using the EyeLink II
system.
NOTE: Please be sure to check http://www.eyelinkinfo.com/news.php for
product and documentation updates as they become available.
1.1 Supporting Documents
This document contains information on using the EyeLink II system; host PC
application, subject setup and calibration, and the basics of running an
experiment. Information on system safety, maintenance, and storage is also
provided. The Appendix A of the current manual explains the use of analog
output and digital inputs and outputs via a DT334 card, if purchased.
Additional documents are also available:
A. EyeLink II Installation Guide – Describes a standard EyeLink II system
layout and environmental considerations as well as the process followed
to install the EyeLink II hardware and software on both the Host and
Display computers.
B. Windows Programmers Guide – Provides suggestions on how to program
experiments with EyeLink II in Windows, including review of all sample
experiments provided for Windows. Document also details the EyeLink II
Windows API.
C. EyeLink Data Viewer User’s Manual – Introduces an optional Data
analysis tool, EyeLink Data Viewer, which allows the displaying, filtering,
and outputting of EyeLink I and EyeLink II EDF data.
D. EyeLink II Scene Camera User Manual – Provides introduction to an
optional tool, EyeLink II Scene Camera, with which the users can track
gaze position on a real world scene video being captured from a head
mounted scene camera.
E. EyeLink II Gaze Overlay User Manual. The optional Gaze Overlay device
works with the EyeLink II system to generate a real-time gaze overlay
graphic on an S-Video source. This option is often used to provide a gaze
overlay onto a dynamic moving scene such as non-static website, AVI file,
or DVD movie, etc. This PAL/NTSC composite or S-Video signal is then
typically saved onto a VCR or DVD recorder for analysis.

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1.2 EyeLink
®
II System Overview
Video-based eye tracking systems have long been acknowledged as the simplest
to set up and operate. However, these systems also had a reputation for low
data rates, poor spatial resolution, high noise, and frequent loss of data. The
EyeLink technology changed all of this with custom-built high-speed cameras
and hyperacuity image processing. EyeLink II has the highest resolution (noise-
limited at <0.01°) and fastest data rate (500 samples per second) of any other
video-based eye tracker today. This exceptional data quality results in very low
velocity noise, making the EyeLink II ideal for saccade analysis and smooth
pursuit studies. On-line gaze position data is available with delays as low as 3
milliseconds, making the system ideal for gaze-contingent display applications.
In addition, on-line data parsing occurs, making eye events such as saccade,
fixation, and blink available within 25 ms to the display computer.
The EyeLink II system consists of two miniature cameras which are mounted
onto a head restraint. No mirrors are used in the EyeLink II system, making it
very robust and easy to set up. Two eye cameras allow binocular eye tracking or
easy selection of the subject's dominant eye without the mechanical
reconfiguration required by most eye trackers. Each camera has built-in
illuminators, digitally corrected for even lighting of the entire field of view.
Together with digital compensation for changes in ambient lighting, this results
in exceptionally stable pupil acquisition.
SR Research is committed to developing EyeLink-based applications to support
most eye-tracking research applications, and will make available software-
development tools for using the EyeLink II data-link and file formats. We will
keep you informed of improvements in documentation and availability of these
tools.
1.3 EyeLink II System Configuration
Figure 1-1: Typical EyeLink II System Configuration

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1.3.1 EyeLink II Host PC
The EyeLink II Host PC performs real-time eye tracking at 250 or 500 samples
per second, while also computing true gaze position on the subject display. On-
line detection analysis of eye-motion events such as saccades and fixations is
also performed. This data can be stored in a data file on the Host PC, sent
through the Ethernet link to the Display PC, or output as analog signals (if the
analog/digital I/O card is installed). From the Host PC, the operator performs
subject setup, monitors performance, and can control applications running on
the Display PC. The Host PC has these key attributes:
•Hosts EyeLink II high-speed eye tracking card, optional analog
output/digital input card.
•Runs a special operating system to host the EyeLink II operator
software. Your original operating system (such as Windows XP) is still
available, if disk the partitioning utility (included with self-installation
kit) is used during installation.
•Functions either as standalone tracker or connected to display computer
through 10BASE-T Ethernet cable.
•In standalone configuration, data output is to hard disk or through
optional analog output card.
•Response box or game pad connected by a USB port.
•Keyboard, display, and pointing device are used to control tracker or as
remote keyboard for applications on display computer.
•EyeLink II software integrates all needed eye tracking functionality,
including subject setup, calibration, real-time data through Ethernet
link or optional analog output card, and writing of data to hard disk.
•Display has real-time feedback of eye data during calibration or
recording, freeing display computer's monitor for calibration target and
stimulus presentation.
•Data File viewing and conversion tools
1.3.2 EyeLink II Display PC
The EyeLink II Display PC provides displays for experiments, and calibration
targets during eye-tracker calibrations. On-line eye and gaze position can be
received from the EyeLink Operator PC via the Ethernet link. Sample

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applications, C source code, and instructions for creating experimental
applications are provided in the EyeLink II Windows developer kit. DOS and
MAC API’s are also available on request. The Display PC has the following key
attributes:
•Runs experiment application software for control of EyeLink II tracker and
stimulus presentation using EyeLink II API, allowing development of
extensive experimental paradigms.
•Display Applications can configure and control the EyeLink tracker, and
have access to real-time data including gaze position, response box button
presses, and keyboard.
•Applications need only support display generation and control of the
experiment sequence, and should rely on the tracker for creating the data
file and reading the response box. This makes millisecond-accurate display
timing possible, even under Windows.
•4 infrared markers (for head tracking) mounted on corners of display.
•Data File viewing and conversion tools

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1.3.3 EyeLink II PCI Card
The EyeLink II PCI card performs the powerful image processing required to
achieve the high temporal and spatial resolution capable with the system. The
PCI card is hosted in the Host PC and has connectors for:
•EyeLink II headband on a 5-meter cable.
•Head tracking markers on a 7-meter cable.
•Ethernet cable for Display PC connection.
1.4 System Specifications
1.4.1 Tracking Modes
Mode Sample Rate Average Delay
(Filter Off/On)
Noise (RMS) Stability
Pupil Only 250 or 500Hz 3 ms / 5 ms / 7 ms < 0.01° Affected by headband
slip and vibration
1.4.2 Operational / Functional Specifications
Image Processing Fully Digital
Pupil Tracking Hyper acuity
Resolution (Gaze) <0.005°
Velocity Noise <3° average
Pupil Size Resolution 0.1% of diameter
Eye Tracking Range ±30° horizontal, ±20° vertical in pupil only
mode.
Gaze Tracking Range ±20° horizontal, ±18° vertical
Built-in calibration, validation Calibration / Validation using Pupil
Operating Environment Tolerates significant indirect IR
Data File EDF
EDF File and Link Data Types Eye position, HREF position, gaze position,
pupil size, buttons, messages, digital inputs

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On-Line Eye Movement Analysis Saccades, fixations, blinks, fixation updates
Real-Time Operator Feedback Eye position cursor during calibration,
validation, and recording. Camera images and
tracking status.
1.4.3 Physical Specifications
EyeLink II Card Half-length PCI (6.8"/176mm) long by 4.2"
(107mm) high.
Camera cable length 4.2 meters
Eye camera distance 40 to 80 mm
Binocular Tracking Standard
Eye Illumination 925 nm IR, IEC-825 Class 1, <1.2 mW/cm2
Ethernet Link TCP/IP or raw, 10BASE-T, built into EyeLink II
card
Response box support USB or digital
Analog output Optional PCI card
Digital Control Configurable
Host Operating system ROMDOS operating system
Display Operating system API Windows (95, 98, NT, 2000, XP), MS-DOS,
Macintosh.
Classification Class II (grounding optional), type BF
(conductive path from computer chassis to
metal parts on the headband)
Power Supply Requirements Powered from host computer power supply,
160W or greater power supply recommended.
Medical-grade power supply is required for
601-1 compliance.
Operating conditions 15°C to 35°C, 20%-80% humidity (non-
condensing), ambient pressure 101 kPa.
Storage conditions -10°C to 40°C, 10%-90% humidity (non-
condensing). Allow to warm to room
temperature before unpacking or use after
storage at temperatures below 10°C.
EyeLink II Card Power Requirements +5V (2A), +12V (0.8A), -12V (0.2A), 22 watts
Electromagnetic compatibility and
immunity
FCC Part 15, Subpart B: Class A unintentional
radiators (see statement below)
CISPR 11:1997 and EN55011:1998 -- Class A,
Group 1 ISM (Industrial, Scientific, and
Medical) Equipment
EN 60601-1-2:1993 – Part 1: General
Requirements for Safety-Collateral Standard
Electromagnetic Compatibility-Requirements
and Tests.

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NOTE: This equipment has been tested and found to comply with the limits for
a Class A digital device, pursuant to part 15 of the FCC Rules. These limits are
designed to provide reasonable protection against harmful interference when
the equipment is operated in a commercial environment. This equipment
generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instruction manual, may cause harmful
interference to radio communications. Operation of this equipment in a
residential area is likely to cause harmful interference in which case the user
will be required to correct the interference at the users’ expense.
WARNING: Changes or modifications not expressly approved by SR Research
Ltd. could void the user’s warranty and authority to operate the equipment.

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2. EyeLink II Tracker Application Operation
2.1 Starting the Host Tracker
To start the EyeLink II Host Tracker follow these simple steps:
a) Start your Host PC
b) If your system was installed with BootMagic, select the EyeLinkII
partition
c) If the EyeLink II Tracker program does not automatically start, type the
following at the command prompt:
cd eyelink2\exe [ENTER]
eyelink2.exe [ENTER]
The EyeLink II Tracker application should start and display the Offline tracker
screen.
2.2 Modes of Operation
The EyeLink II is a multipurpose, high resolution, real-time processing system.
It is designed to be used in 2 different primary operation modes:
Link: In this mode, the eye tracker is partially controlled by the Display PC via
the Ethernet link. The degree of Display PC control is dependent only on the
display application itself. It is possible to have full control of the tracker via the
Display PC; however this also requires the most display application
programming. A common scenario is to have the application on the display PC
control the eye tracker to start subject setup and calibration, while the operator
uses the EyeLink II Host PC's keyboard to remotely control the application,
perform drift correction, and handle problems if they occur.
Standalone: In this mode, the eye tracker is an independent system, controlled
by the operator by the Host PC tracker interface and keyboard. The Host PC is
still connected to a display-generating computer for the purpose of displaying
calibration targets only. There are 2 possible data output modes when running
the EyeLink II as a standalone system. These output modes are not exclusive
and include:

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a) Analog output. Using the optional analog output card, data is available
in analog format. Analog output options are configurable via the “Set
Options” screen and in the analog.ini initialization file.
b) File Output. Eye data is available in the EyeLink II EDF file format.
This can be converted to an ACSII file format using the edf2asc
conversion utility. File output options are configurable via the “Set
Options” screen.
2.3 EyeLink II Tracker Application Navigation
The EyeLink II tracker interface consists of a set of setup and monitoring
screens, which may be navigated by means of the host PC mouse, key
shortcuts, or from the Display PC application via link commands.
Figure 2-1: Screen Overview of EyeLink II Tracker Program
Each of the modes shown in the diagram above has a special purpose. Where
possible, each screen has a distinctive appearance as shown in the figure.
Screens with gray bars contain menus of key options for navigation and setup.
Other screens have a key-navigation bar at the top of the screen and a status
bar at the bottom. Arrows represent the navigations possible by keys: any
mode is accessible by link control. Note the central role of the Setup menu: it
serves as the mode control during subject setup.

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The functions of each mode and the main access keys to other modes are
summarized below. Pressing the on screen Help button or hitting the F1 key
will open a screen sensitive Help menu listing all available key shortcuts for
that screen. From any screen, the key combination ‘CTRL+ALT+Q’ will exit the
EyeLink tracker program.
2.3.1 Offline Screen
Figure 2-2: EyeLinkII Offline Screen
2.3.1.1 Purpose
The off-line mode is the default start-up screen for EyeLink II. The main
secondary screens can be accessed via the navigation buttons on the left hand
side of the screen.
2.3.1.2 Main Functions
Press to go to the camera setup
screen.
Keys: ENTER = Camera Setup
Select Output to go to the output
Ethernet
Connection
Status
Camera view with threshold status
Screen
N
avi
g
ation

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screen, from which you can start a
manual recording session.
Keys: O = go to Output screen
Select Set Options to go to the EyeLink
II options screen, where a variety of
system options and settings can be
configured. Note that any value on this
screen can be programmatically
overridden by the API during
experiment setup.
Keys: S = go to Set options
Select Exit EyeLink to end the EyeLink
II program.
Keys: Ctrl + Alt + Q = Exit EyeLink
Press Help (F1) to access the online
help page for Camera Setup. All
available key shortcuts are also listed
on the Help screen.
Keys: F1 = open Help screen
2.3.1.3 Key Shortcuts
ENTER Press to enter camera setup
O Press to go to the Output screen
S Press to go to the Set Options screen
Ctrl + Alt + Q Press to exit the EyeLink program
F1 Press to view the Help screen, in the
help screen there is a brief overview of
the role of this page and the key
functions for it.

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2.3.2 Camera Setup Screen
Figure 2-3: EyeLink II Camera Setup Screen
2.3.2.1 Purpose
This is the central screen for most EyeLink II setup functions. From this screen
the eye and head tracking cameras can be set up, and their images can be
thresholded. Eye(s) to be tracked, tracking mode and options can also be set.
Calibration, Validation, and Drift correction can also be performed from this
screen.
Image Display Attributes
Tracking Mode
Sl ti
Camera Select and Status
Ctl
Selected eye(s) to track

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2.3.2.2 Main Functions
Press Auto Threshold to threshold the
selected camera image. In most cases
auto thresholding will set the correct
image threshold for the camera.
Keys: A = Auto threshold selected
image
Use the arrow buttons to manually
increase or decrease the selected
camera’s pupil threshold.
Keys: ⇑and ⇓= increase and decrease
threshold
Select the sampling rate for recording.
Here 250 Hz is selected. Note that in
Pupil-CR mode, 500Hz is not available.
Keys: F = toggles sampling Frequency
selection
Toggles display of crosshair in eye
camera images.
Keys: X = toggle crosshair display
Toggles display of threshold coloring in
eye camera images.
Keys: T = toggle threshold coloring
display
Select to present the camera display
image on the Display Monitor.
To select the camera to display as a
large image click on the desired image
thumbnail. The selected image
thumbnail has a heavy border around
it. Here the Right Eye camera is
selected. Image thresholds and status
are indicated below each thumbnail.
Keys: ⇐and ⇒to move left or right
on image row