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.

EyeLink II User Manual version 2.12 (07/02/2006) ©2002-2006 SR Research Ltd.
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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

EyeLink II User Manual version 2.12 (07/02/2006) ©2002-2006 SR Research Ltd.
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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