EyeLink® User Manual For EyeLink models: EyeLink 1000 EyeLink 2000 EyeLink Remote Tower, Desktop, Arm and Primate Mounts Version 1.4.0 Copyright ©2005-2008, SR Research Ltd. EyeLink is a registered trademark of SR Research Ltd.
Read instructions before use. Entela Safety Mark: Compliance of this product with UL 60950 3rd Edition, CSA C22.2 No 60950-00-CAN/CSA is certified by Entela, an independent testing body. US C Certified CLASS 1 LED DEVICE IEC 60825-1 (Ed. 1.2:2001) CAUTION: Use of controls or adjustments or performance of procedures other than those specified herein may result in hazardous radiation exposure.
Table of Contents 1. Introduction .............................................................................................................. 1 1.1 Supporting Documents......................................................................... 3 1.2 EyeLink 1000 System Configuration ..................................................... 4 1.2.1 Host PC .......................................................................................................... 4 1.2.2 Display PC........................
3.2.6 Desktop Mount (Angled) Participant Setup, Binocular ................................. 62 3.3 Setting Pupil Threshold ...................................................................... 65 3.4 Setting Corneal Reflection (CR) ........................................................... 67 3.5 Search Limits ..................................................................................... 68 3.6 Pupil Tracking Algorithm ....................................................................
4.4.4 4.5 Events................................................................................................ 93 4.5.1 Messages ..................................................................................................... 93 4.5.2 Buttons ......................................................................................................... 94 4.5.3 Eye Movement Events.................................................................................. 94 4.6 Setting File Contents .......
7.3 Setting up the EyeLink 1000 Analog Card ......................................... 121 7.3.1 Installing Analog Output Hardware ............................................................. 121 7.3.2 Connections to Analog Card....................................................................... 122 7.3.3 Noise and Filtering...................................................................................... 122 7.4 Digital Inputs and Outputs.....................................................
List of Figures Figure 1-1: Typical EyeLink 1000 Configuration (Tower Mount) ........................ 2 Figure 1-2. EyeLink 1000 Desktop Mount with Camera Level and Angled ......... 6 Figure 1-3. EyeLink 1000 Tower Mount ........................................................... 6 Figure 2-1: EyeLink 1000 Host PC Application Overview .............................. 13 Figure 2-2 Offline Screen ...............................................................................
Figure 3-15. Camera Setup with Subjects Wearing Glasses (Desktop Mount – Camera Angled). ...................................................................................... 65 Figure 3-16: Symptoms of Poor Pupil Threshold ........................................... 66 Figure 3-17: Corner Effects Seen with Head Rotation ................................... 67 Figure 3-18: Corneal Reflection...................................................................... 67 Figure 3-19. Calibration Grid...........
1. Introduction This section introduces the technical capabilities and supporting documentation for the EyeLink 1000, EyeLink 2000 and EyeLink Remote eye trackers (henceforth referred to as the EyeLink 1000). The EyeLink 1000 comes in several configurations, each with its own strengths, weaknesses and capabilities, allowing it to suit a wide variety of research settings. The same camera and software support all configurations, making it the most versatile solution for eye and gaze monitoring available.
Figure 1-1: Typical EyeLink 1000 Configuration (Tower Mount) All configurations of the EyeLink 1000 operate at the unparalleled low variability required for accurate gaze contingent paradigms, and the highly accurate and sensitive operation that careful research demands. EyeLink systems are the only modern equipment to run on a real-time operating system for low variability in near-instant access to eye data measures.
1.1 Supporting Documents This document contains information on using the EyeLink 1000 hardware, the Host PC application, tutorials on subject setup and calibration, and the basics of running an experiment. Information on system safety, maintenance, and storage is also provided. Appendix A of this manual explains the use of the optional analog output and digital inputs and outputs via a DT334 card. Additional documents are also available: A.
1.2 EyeLink 1000 System Configuration 1.2.1 Host PC The EyeLink 1000 Host PC performs real-time eye tracking at 250, 500, 1000, or 2000 1 samples per second with no loss of spatial resolution, while also computing true gaze position on the display viewed by the subject. On-line detection analysis of eye-motion events such as saccades and fixations is performed.
• Real-time feedback of eye data is available on the Host PC during calibration or recording, allowing other network devices to be devoted to accurate stimulus delivery. 1.2.2 Display PC The EyeLink 1000 Display PC administers eye tracker calibration , directs data collection, and presents stimuli during experiments. On-line eye and gaze position can be received from the EyeLink Host PC via the Ethernet link making gaze-contingent paradigms possible.
Desktop Mount (Level) Desktop Mount (Angled) Figure 1-2. EyeLink 1000 Desktop Mount with Camera Level and Angled 1.2.3 EyeLink 1000 Camera Mount Configurations The EyeLink 1000 is available in four base hardware configurations (Desktop, Tower, Arm and Primate Mounts). These configurations differ in the type of mounting used for the EyeLink CL high speed camera and low output infrared illuminator module.
The EyeLink 1000 Tower Mount (Figure 1-3) incorporates the camera and illuminator housing within a combined chin and forehead rest via an infrared reflective mirror. Mirror angle and chin position are adjustable for increased compatibility with eyeglasses. The Tower Mount affords the largest field of view of all mounting systems for the EyeLink 1000 high speed camera. Figure 1-4.
The EyeLink 1000 Arm Mount (Figure 1-5) is a fully adjustable arm holding a 17” LCD monitor with the camera and illuminator mounted beneath it. When fixed on a sturdy table the entire apparatus can be moved in place in front of the viewer to allow access to difficult to track populations, or simply to hold the eye tracker at an appropriate height to accommodate a sitting viewer. 8 Introduction © 2005-2008 SR Research Ltd.
1.3 System Specifications 1.3.1 Operational / Functional Specifications Tower Mount Desktop and Arm Mounts Base Remote Option (license required) System Primate Mount down to 0.15° (0.25° to 0.5° typical) Average Accuracy1 0.5° typical Monocular: Monocular: 250, 500,1000, 2000 Hz Sampling rate2 250, 500 Hz Binocular*: 250, 500, 1000 Hz End-to-End Sample Delay3 Blink/Occlusion Recovery M < 1.8 msec, SD < 0.6 msec @ 1000 Hz M < 3.0 msec, M < 1.4 msec, SD < 0.4 msec @ 2000 Hz SD=1.11 msec M < 1.
1.4 Physical Specifications EyeLink 1000 Card Eye Illumination Half-length PCI 140 mm long by 100 mm high. CLASS 1 LED PRODUCT (IEC 60825-1 Ed.1.2:2001) Wavelength: 910 nm (Tower and Primate Mounts) 890 nm (Desktop and Arm Mounts) Tower/Primate Mount Eye illumination level: less than 1 mW/cm² at >200mm from illuminator. Desktop/Arm Mount Eye illumination level: less than 1 mW/cm² at >300mm from illuminator.
CLASS 1 LED DEVICE IEC 60825-1 (Ed. 1.2:2001) 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.
2. EyeLink 1000 Host Application 2.1 Starting the Host Tracker Follow these simple steps to start the EyeLink 1000 Host Tracker: a) Start your Host PC b) If your system was installed with a disk partitioning tool, select the EyeLink partition c) Type the following at the command prompt: T [ENTER] d) If the EyeLink 1000 Tracker program does not start, type the following at the command prompt: CD ELCL\EXE [ENTER] ELCL.
when running the EyeLink 1000 as a standalone system. These output modes are not exclusive and include: 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 EDF file format (see Chapter 4 “Data File”).
bar at the bottom. Arrows represent the navigations possible by key presses on the Host PC keyboard or via button selection using the Host PC mouse. All modes are accessible from the Display PC by link control. Note the central role of the Camera Setup menu: it serves as the mode control during subject setup. The functions of each mode and the main access keys to other modes are summarized below.
Click “Set Options” for access to a variety of EyeLink 1000 options and settings on the Set Options screen. Note that any value on this screen can be over-ridden during experiment setup by commands coming from the Display PC. Keyboard Shortcuts: S = go to Set Options Click “Exit EyeLink” to end the EyeLink 1000 Host PC application. Keyboard Shortcuts: Ctrl + Alt + Q = Exit EyeLink Click “Help (F1)” to access the online help page for the Offline screen.
Figure 2-3 Set Options Screen 2.3.2.2 Set Options Screen Main Functions Select the Calibration Type for recording. The more locations sampled, covering the greatest space, the greater the accuracy that can be expected. Here, a nine-point calibration is selected. Note that not all Calibration Types are available using the EyeLink Remote option.
If enabled, requires the manual pressing of the spacebar or ENTER key on Host or Display PC in order to gather the sample when the subject is looking at each calibration or validation target. If disabled, the calibration and validation procedure automatically samples once the eye settles on a target. Keyboard Shortcuts: Y = toggle Force Manual Accept on/off. Clicking the Camera Position Detect button polls the position of the camera selection knob to determine the eye to track.
Select whether to record eye events (fixations and saccades) in Gaze or HREF coordinate. GAZE is screen gaze x, y; HREF is head referenced-calibrated x, y Keyboard Shortcuts: E = alternates between Gaze and HREF settings Defines the sensitivity of the EyeLink 1000 parser for saccade event generation. Normal is intended for cognitive tasks like reading; while High is intended for psychophysical tasks where small saccades must be detected. See Section 4.3.5 Saccadic Thresholds for details of event parsing.
Select the tracker configuration. Each configuration consists of the Camera Mount Type (Desktop, Arm Mount) with the Camera Mode or Orientation (Remote, Level, Angled) in parentheses. Additionally are two types of Desktop Mount – one with the Illuminator on the Left and the Camera on the Right (ILLUM—CAM – illustrated in the Figure at left), and the other with these reversed. Your Host PC should have the software configured for your mount.
Selecting Samples will record data samples to the EDF file, and selecting Events will record on-line parsed events. Keyboard Shortcuts: F = alternates selection of Samples and Events buttons Record the raw (x, y) coordinate pairs from the camera to the EDF file Keyboard Shortcuts: 3 = toggle record Raw Eye Position on/off Record head-referenced eye-rotation angle (HREF) to the EDF file. Keyboard Shortcuts: 4 = toggle record HREF Position on/off Record gaze position data in the EDF file.
Clicking “Video Setup” goes to the Video Setup screen. Clicking “Enable Overlay” activates the video overlay option. Keyboard Shortcuts: V= toggle video setup; O= toggle video overlay on/off These settings control what to show on the Record screen during data output. If Record View is set to Gaze Cursor, the Host PC Record screen will display the participant’s current gaze position as a cursor graphic overlaid on a simulated display screen.
V O F6 F7 ENTER ESC F1 L Select to view video setup screen, if the overlay option is enabled. toggle on/off video overlay option. Select Record view (plot or gaze cursor). Select Record Plot Data Type. Camera Setup screen Return to previous screen HELP screen Revert to configuration from last session. This is still saved even when the PC is turned off. Load default configuration (DEFAULTS.INI) D 2.3.2.4 Table 2.
2.3.3.2 Camera Setup Screen Main Functions Click “Auto Threshold” to have the Host PC compute threshold levels automatically. Fine tuning may be necessary. The EyeLink Remote dynamically adjusts threshold levels that are further biased by threshold adjustments. Keyboard Shortcuts: A = Auto Threshold selected image Clicking these buttons manually increases or decreases the selected pupil threshold (Tower or Desktop Mounts) or pupil threshold biases (EyeLink Remote).
Toggles display of threshold coloring (blue for pupil, yellow for corneal reflection) in camera images. Keyboard Shortcuts: T = toggle ring in display Select to present the camera display image on the Display PC monitor.
Tower Mount: Desktop Mount (Angled): Desktop and Arm Mounts (Level) /Remote (Level): Select the eye to track during recording. Here the Left eye is selected. Tower Mount: Clicking “Camera Position Detect” polls the position of the camera selection knob indicating which eye is selected for tracking. Desktop Mount (Angled): The “Lock Tracked Eye” button disables the ability to switch the eye being tracked from the Display PC (as will pressing ‘K’).
Click Help (F1) to access the online help page for Camera Setup. All available key shortcuts are listed on the Help screen. Keyboard Shortcuts: F1 = open Help screen Click ‘Calibrate’ to go to the Calibrate screen. After setting up the camera and adjusting thresholds (EyeLink 1000 and EyeLink 2000) or biases (EyeLink Remote), you need to calibrate the system. Keyboard Shortcuts: C = go to Calibrate screen Click ‘Validate’ to go to the Validate screen.
2.3.3.
2.3.4 Calibrate Screen 2.3.4.1 Calibrate Screen Purpose Calibration is used to collect fixation samples from known target points in order to map raw eye data to either gaze position or HREF data. Targets are serially presented by the Display PC. The participant fixates each while samples are collected and feedback graphics are presented on the Host PC display. The calibration is automatically checked when finished, and diagnostics are provided.
2.3.4.2 Calibrate Screen Main Functions Click to go to the Camera Setup screen. Keyboard Shortcuts: ENTER = Camera Setup Click to see Help and keyboard shortcuts. Keyboard Shortcuts: F1 = Help screen Terminate Calibration sequence. Keyboard Shortcuts: ESC = Abort Restart the Calibration Click to automate the calibration sequence according to the Pacing Interval from the Set Options screen. Keyboard Shortcuts: A = Auto Trigger Press to accept calibration fixation.
2.3.5 Validate Screen Figure 2-6 Validate Screen 2.3.5.1 Validate Screen Purpose The Validate screen displays target positions to the participant and measures the difference between the computed fixation position and the fixation position for the target obtained during calibration. This error reflects the gaze accuracy of the calibration. The functionality available in the Validate screen is very similar to that of the Calibrate screen. Validation should only be performed after Calibration.
Click to Restart the Validation process Click to automate the validation sequence according to the Pacing Interval from the Set Options screen. Keyboard Shortcuts: A = Auto Trigger Press to accept fixation value, after the participant’s gaze is stable on the target. Keyboard Shortcuts: ENTER, Spacebar = Accept Fixation 2.3.5.3 Validate Screen Key Shortcuts Key Function F1 ESC A Help screen Camera setup Auto calibration set to the pacing selected in Set Options menu. (Auto trigger ON).
2.3.6 Drift Correct/Drift Check Screen 2.3.6.1 Drift Correct/Drift Check Screen Purpose Figure 2-7. Drift Correct/Drift Check Screen The Drift Correct screen displays a single target to the participant and then measures the difference between the computed fixation position during calibration and the current target. For the EyeLink 1000, the default configuration leaves the calibration model unmodified. The purpose therefore, is to check whether the model has become grossly invalidated.
2.3.6.2 Drift Correct/Check Screen Main Functions Click to go to the Camera Setup screen. Keyboard Shortcuts: = ESC Click to view Help for the Drift Correct with a brief overview of the role of drift correction. Keyboard Shortcuts: = ENTER Stop the Drift Correction. Restart the Validation process Not Used Press to accept fixation value, only when the participants gaze is stable. Keyboard Shortcuts: ENTER, Spacebar = Accept Fixation 2.3.6.
Figure 2-8 EyeLink 1000 Output Screen 2.3.7.
F X M Opens EDF File Closes EDF File Add a message to the EDF file. 2.3.8 Record Screen 2.3.8.1 Record Screen Purpose The Record screen allows direct access to initiating data collection. The user can choose either a Gaze View (see Figure 2-9) or Plot View (see Figure 2-10) of the Record screen by toggling the “Plot View” button. Figure 2-9 Record Screen (Gaze Cursor View) The Gaze Cursor View plots the current gaze position of the subject in calibrated screen pixel coordinates.
The Plot View displays the x, y data traces as a function of time. The type of data to be plotted can be configured at the Set Options screen. Since raw data can also be displayed in the plot view, this view is useful in any data output mode, even when calibration has not been performed. 2.3.8.2 Record Screen Main Functions (Gaze View and Plot View) Stops the recording of data to the EDF file. Keyboard Shortcuts: ESC = Stop Recording Abort the trial recording.
position where the traces are displayed can be changed by clicking on the ⇑ and ⇓ buttons in the “Scroll” section. For RAW and analog outputs, the user can adjust the “gain” and “offset” values and therefore this provides a way for user to “calibrate” data in the recording screen. This might be useful for experiments with primates or patients where the 9 point calibration method is not possible.
Selects zooming level (or use ALT + ⇑ and ALT + ⇓ keys). These buttons will only be available when the plotting data type is Gaze, Angle, or HREF. Keyboard Shortcuts: ALT + ⇑/⇓ = Adjust zooming levels Sets the gain value when used with mouse or ALT+ ⇑ and ALT+ ⇓ keys. These buttons will only be available when the plotting data is RAW or Analog. Keyboard Shortcuts: ALT + ⇑/⇓ = Adjust gain values Scrolls the eye traces up or down (or use CTRL + ⇑ and CTRL + ⇓ keys).
F On-line Offset correction. Plot Mode Only (Recording Screen). X or Y Data trace to select or view < or > Change plot speed P Pause or unpause plotting (also marks) INS Adds rewinding marker DEL Rewind to marker or start HOME Clear all data U Undo last view or gain/offset change. C Change to default view or gain/offset. TAB Fit all data to view, auto gain/offset adjusting CTRL Selects offsets or scrolling when used with mouse or ⇑ and ⇓ keys.
4) Click at the blank space next to the graph. A green marker will appear at intended value. For the ease of adjustments, you may set that point close to center of the left- and right-eye traces. Also note that a white bar at the right end of the graph. This bar sets the upper and lower bounds for gain and offset adjusts. 5) To adjust the gain of eye traces, place the mouse cursor outside of the regions bounds by the white bar.
of every experiment. A visual indicator, illustrated in the figure below, is present on the right hand side of the Calibrate, Validate, Drift Correct, Output and Record screens and gives the operator a complete and continuous status report of the camera image.
2.5 Mouse Simulation Mode You can use a mouse on the EyeLink 1000 Host PC to simulate an eye to practice calibration and tracking alone or to test experiments during development if a test subject is not available. Select “Mouse Simulation” in the “Set Options” screen to enable mouse simulation. If the mouse is not moving at your intended location, you may first perform a calibration on the mouse device (See section 3.7 “Calibration”). 2.
BUTTONS.INI Hardware definition of buttons, special button functions. Preconfigured for Microsoft SideWinder Plug & Play. CALIBR.INI Commands used to control the calibration settings. COMMANDS.INI Lists some useful EyeLink commands for controlling the host application via your own program. DATA.INI Specifies where EDF files should be written to on Host PC. Controls data written to EDF files, link. DEFAULTS.INI Default settings for all items in LASTRUN.INI: can be loaded from Setup menu. EL1000.
If you plan to change the default settings in the .INI files, please copy and paste the target commands to the FINAL.INI and make the modification in that file for the ease of future maintenance. 44 EyeLink 1000 Host Application © 2005-2008 SR Research Ltd.
3. An EyeLink 1000 Tutorial: Running an Experiment The following tutorial will demonstrate and test the EyeLink 1000 system, assuming that you have already arranged a proper layout of the EyeLink 1000 equipment and configured PHYSICAL.INI for your setup (see Section 1.1 “Suggested Equipment Layout” and Section 10 “Final Installation steps” of the “EyeLink 1000 Installation Guide” document). A summary of the setup procedure can be found at the end of the discussion (“3.13 EyeLink 1000 Setup Summary”).
3.1 The Camera Setup Screen The first step in an eye-tracking session is to set up the participant and eye tracker. Begin by pressing ↵ (ENTER) on the Host PC’s keyboard to display the Camera Setup screen. You will see two camera-image windows in the middle of the display, a global view of the tracked eye on the top and a zoomed view at the bottom. Navigation button to access other Tracker screens are on the right, while selection buttons for tracking mode and other functions are on the left of the screen.
Because all keys on the subject keyboard are sent to the EyeLink software by TRACK, you can practice calibration and observe your tracked eye-position too. Since no menus appear on the Display PC, you will have to be able to see the Host PC display as well. NOTE: Ideally, to prevent small drifts in thresholds, EyeLink 1000 electronics should be powered for about 5 minutes before recording.
Figure 3-2: Parts of the EyeLink 1000 Tower Mount then tighten the knob. Click on the “Camera Position Detect” button on the Camera Setup screen to check whether the correct eye is highlighted.
IMPORTANT: The height of the EyeLink 1000 Tower should not be adjusted when a subject is using the head support device! If the subject wears glasses, start with the mirror angle to middle- or highposition and then gradually adjust it during the camera setup process if necessary. The “Use Search Limits” button should also be checked so that the tracker will try to re-acquire the pupil position within a red box illustrated in the global view of the camera image.
the pupil is detected, a green box and the cross now will be drawn on the eye image. If the image becomes too dark or too light, wait one second while the autocontrast adjusts itself. If the blue thresholded area in the display is interfering with setup, press the “Threshold Coloring” button (or ‘T’ on the keyboard) to remove the threshold color overlay. In TRACK.EXE, you can use keys on either the Display or Host PC to perform all keyboard shortcut operations while the eye image is displayed.
every joint. Furthermore, the LCD display can be tilted forward or backward and rotates around the swivel joint that attaches it to the Arm. Ideal positioning of the Arm Mount places the LCD display: • perpendicular to the viewer’s line of sight, • with their gaze centered, and • intercepting the top of the display.
1) First, check whether the 35 mm lens (without a focusing arm or ring) has been installed. The 25 mm lens (with a long focusing arm) may be useful for distances closer than about 40 cm. 2) For the Desktop Mount, check that the camera is set to the horizontal position – the elongation of the camera should be parallel to the top of the mount (see the figure below). If not, please loosen the Camera Screw and move it to the top end of the slot.
Ask the subject to be seated. Adjust the height of the chair so that the subject is comfortable and his/her eye line is aligned to upper half of the monitor. Ask the subject to lean her/his forehead against the forehead rest and adjust the height of the chinrest so that the subject’s chin sits comfortably on the chin rest pad. If necessary, loosen the Lock knob on the Desktop Mount to adjust the tilt of the camera so that the intended eye image appears in the center of the global view of the camera image.
Figure 3-6. Camera Setup with Subjects Wearing Glasses (the EyeLink 1000 Monocular Mount). If the image becomes too dark or too light, wait one second while the autocontrast adjusts itself. If the blue thresholded area in the display is interfering with setup, press the “Threshold Coloring” button (or ‘T’ on the keyboard) to remove the threshold color overlay. In TRACK.EXE, you can use keys on either the Display or Host PC to perform all keyboard shortcut operations while the eye image is displayed.
By default, the “Illuminator Power” level is set to 75% at the recommended distance. If the Desktop Mount is placed too further away from the observer or if you find the pupil is not reliably acquired, you may consider increasing the illumination level to 100%. Now proceed to section 3.3 “Setting Pupil Threshold”. 3.2.4 EyeLink Remote Participant Setup The EyeLink Remote is designed for applications where a chin rest or head mount is not desirable or perhaps even possible (i.e.
destroy your .SCD file, a copy should be safely stored on the CDs you received with your EyeLink 1000. 4) The height of the Display PC monitor should be set so that when the participant is seated and looking straight ahead, they are looking vertically at the middle to top 75% of the monitor.
7) The EyeLink Remote uses a small target sticker placed on the participants’ forehead. This allows tracking of head position even when the pupil image is lost (i.e., during blinks or sudden movements). For the largest lateral movement range of the subject, track the eye that is on the same side of the midline as the illuminator. For instance, if the illuminator is to the left of the camera, the largest lateral movement range will be associated with the subject’s left eye.
8) Place one of the EyeLink Remote target stickers on the subject’s forehead (see Figure 3-12), just above the eyebrow of the tracked eye so that both the eye and the sticker stay within the camera image when the subject’s head moves throughout the expected range.
overlaid with a blue threshold overlay. If the blue area in the display is interfering with setup, press the “Threshold Coloring” button (or ‘T’ on the keyboard) to remove the threshold overlay. In TRACK.EXE, you can use keys on either the Display or Host PC to perform all keyboard shortcut operations while the eye image is displayed. Threshold bias too low Properly thresholded Threshold bias too high Figure 3-10.
15) The operator can easily tell if the pupil has been detected because the image on the Host PC will have a crosshairs indicating its center. A green ellipse, updated each refresh, is drawn around the elliptical pupil fitting algorithms (see section 3.6 “Pupil Tracking Algorithm”). If a shadow interferes with pupil detection, or if the eye image is clipped by the side of the camera window, the crosshair and ellipse fitting will disappear and the pupil will be lost.
result, the recorded data will be noisy. If this happens, first check whether the subject is seated at the recommended eye-target distance of 550-600 mm. Dimmer room lighting will also help avoid this warning. Pupil size looks OK Pupil size warning (size too small) Figure 3-11.
3.2.5 Primate Mount Participant Setup, Monocular Most of the details for Primate Mount setups are detailed in the Installation Guide. Once a physical setup is established, there is unlikely to be much variation in the steps taken to track eye movements as there is generally little variability in the view of the eye or the participants.
the illuminator should be as close as possible to the lower edge of the visible part of the monitor for maximum eye tracking range. 6) Start the EyeLink host application and click “Set Options” button. Check the “ELCL Configuration” is set to “Desktop (Angled)”. 7) Ensure the lens cap has been removed from the camera by pulling the cap outwards while holding the camera. Figure 3-13: Position and Angle of the Camera for EyeLink 1000 Desktop Monocular vs.
dotted line does not appear horizontally centered, move the Desktop Mount to the left or right or rotate the angle of the Desktop Mount slightly. Important, even if the binocular mount is used for monocular eye tracking, the dotted line should also be aligned with the center of the face. Figure 3-14.
Figure 3-15. Camera Setup with Subjects Wearing Glasses (Desktop Mount – Camera Angled). If the image becomes too dark or too light, wait one second while the autocontrast adjusts itself. If the blue thresholded area in the display is interfering with setup, press the “Threshold Coloring” button (or ‘T’ on the keyboard) to remove the threshold color overlay. In TRACK.EXE, you can use keys on either the Display or Host PC to perform all keyboard shortcut operations while the eye image is displayed.
threshold may now be automatically set by pressing the ‘Auto Threshold’ button or the ‘A’ key when the camera image is selected. The pupil of the eye should be solidly blue, with no other color in the image when the thresholding is properly set. If large areas are colored, the subject may have blinked: press Auto Threshold again. If the subject wears eyeglasses, reflections may block the pupil in the image.
In general, after threshold adjustment, pupil thresholds should be between 75 and 110 and corneal thresholds should not exceed 230. If the pupil threshold is too low, try increasing the illumination output. If the pupil threshold or corneal thresholds are too high, try reducing the illuminator output.
Follow the following steps to acquire the best CR: a) Press the Auto Threshold button to set the CR threshold. You should see a yellow circle appear near the pupil on each eye. Auto Threshold should almost always set the correct CR threshold. b) If the auto thresholding sets the threshold too low or high, use the CR threshold buttons, or the + and – keys, to manually adjust the CR threshold.
height; ALT + ⇐ and ⇒ to adjust the width). The position of the search limits can be adjusted with SHIFT and cursor keys. In a binocular setup, size/position of the search limits can be adjusted for each of the eyes separately. 3.6 Pupil Tracking Algorithm The EyeLink 1000 implements two pupil tracking algorithms: Centroid vs. Ellipse Fitting.
• Randomize target order: YES • Auto-trigger pacing: 1000 msec Press the “Previous Screen” button when done to return to Camera Setup. Begin calibration by pressing the ‘Calibrate’ button from the Camera Setup menu. A calibration target will appear on both the Host PC display and the Display PC monitor. The subject display is drawn by the TRACK.EXE application, in response to commands from the EyeLink tracker.
If automatic sequencing has been enabled, targets will be presented and fixations collected without further intervention. Each time a new target is displayed, the subject quickly makes a saccade to it. The EyeLink 1000 system detects these saccades and the fixation following, producing an automated sequencing system. NOTE: Sequencing may halt if the setup of the eye causes pupil loss or noise at the target position. If this happens, adjust the threshold and restart the calibration by pressing the ‘ESC’ key.
When the last calibration target has been presented, the calibration will be evaluated. At the bottom of the Calibration screen, each eye's calibration is graded and displayed as follows: GOOD (green background): No obvious problems found with the data FAILED: (red background): Could not use data, calibration must be repeated The background color of the message indicates the usability of the calibration. We must still validate the accuracy of the calibration: only serious problems can be detected here.
The pupil status error message “MISSING” highlighted in red, indicates that the pupil is missing from the camera view. This could be that the participant is blinking. It could also be that there is a problem with camera setup. Please adjust as needed. Indicates Status of Corneal OK = Corneal is visible MISSING = Corneal is missing The corneal status error message “MISSING”, highlighted in red, indicates that the corneal reflection is not visible to the camera. See section 3.
To begin the validation procedure, select the “Validate” button or press the ‘V’ key in the Camera Setup screen. The Host PC display will show the gaze position as a round colored cursor. Note the movements of the cursors, and the change in relative horizontal position (vergence) following saccades. Once the cursor appears stable, and close to the target, press the ↵ (ENTER) key to accept the first fixation. The remaining points are collected automatically or manually, as in the calibration process.
• Always ask the subject to look at the four corners of the display after performing the camera setup. Watch for the warning signals on the tracker screen to make sure that the pupil and CR signal is not lost when the subject is doing so. • 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.
subject’s inattention. Applications can create similar feedback displays by sending the display screen image to the tracker PC before recording begins. TRACK displays the gaze position as a red cursor on the subject display. The cursor can be toggled on and off by the ‘G’ key on the Display PC keyboard. To implement this feedback, TRACK requests that EyeLink send it 250, 500, 1000, or 2000 samples per second of gaze-position via the EyeLink Windows DLL. This data is used to move the gaze cursor.
sending this as a command in your program. When the subject looks at the reference position, pressing ‘F9’ key on the Host PC or sending an “online_dcorr_trigger” command over the link will perform the drift correction. Alternatively, an online drift correction can be performed with the aid of a mouse click. Before recording, add the following line to the FINAL.INI file: Normal_click_dcorr = ON Figure 3-20.
3.13 EyeLink 1000 Setup Summary It is suggested that you try the procedures in this section until you feel comfortable with the EyeLink 1000 setup, and can get reliable calibrations. This is a summary of the steps detailed in the practice session. It assumes no setup problems are encountered. • Start the EyeLink 1000 Host application • Start TRACK.EXE on the Display PC. • Have the subject seated in the chair comfortably.
3.14 Experiment Practice The TRACK.EXE program is the most flexible way to practice the EyeLink 1000 setup, allowing almost any sequence of actions to be performed. In real experiments, the sequence of actions is much more defined. Usually the experiment begins with subject setup and calibration from the Setup menu, perhaps followed by practice trials. Then a series of experimental trials are performed, sometimes with a drift correction before each trial.
ii. Create a full-screen window, and send a series of commands to the tracker to configure its display resolution, eye movement parsing thresholds, and data types. iii. Using a dialog box built into the EyeLink programming library, ask for a file name for an EDF data file, which it commands the EyeLink tracker to open on the Host PC hard disk. iv. Run a block of trials.
The “Eyedata” template uses link data to display a real-time gaze cursor. The data is then played back after the trial, drawing the saccade paths and fixation points to the screen. The bitmap for the trial is a grid of letters. E. GCWindow The most useful real-time experiment is a gaze-contingent display, where the part of the display the subject is looking at is changed, or where the entire display is modified depending on the location of gaze.
4. Data Files The EDF file format is used by the EyeLink tracker and supporting applications to record eye-movements and other data. It is designed to be space-efficient and flexible, allowing for complete records of experimental sessions and data. It adapts to monocular and binocular recording, with backwards-compatibility for future enhancements. The EyeLink 1000 EDF file format is backwards compatible with the original EyeLink and EyeLink II EDF file format.
be used to record the time of a change in the display, or an experimental condition. 4.2 Recording EDF Files EDF files are created by the EyeLink 1000 tracker, recording eye-position data, events from the on-line parser, and button and input events. These are recorded only when the tracker is in output (recording) mode. Messages sent from applications on the Display PC through the Ethernet link may be recorded at any time.
4.3.1 Parser Operation The parser uses velocity and acceleration-based saccade detection methods. Because of the EyeLink 1000 tracker’s exceptionally low noise levels and high spatial resolution, very little data filtering is needed and thus delay is kept small. The 250, 500, 1000, or 2000 Hz sampling rate gives a high temporal resolution of 4, 2, 1, or 0.5 millisecond (Note: Availability of some sampling rates and options depends on the system model).
with EyeLink Data Viewer or convert the EDF file to an ASC file to see the correspondence between eye movements and the parser output. 4.3.3 EyeLink Parser Configuration The saccadic detection parameters for the EyeLink 1000 on-line parser may need to be optimized for the type of experimental investigation being performed.
detection of saccades as small as 0.3°, ideal for smooth pursuit and psychophysical research. A conservative threshold of 30°/sec is better for reading and cognitive research, shortening saccades and lengthening fixation durations. The larger threshold also reduces the number of microsaccades detected, decreasing the number of short fixations (less than 100 msec in duration) in the data. Some short fixations (2% to 3% of total fixations) can be expected, and most researchers simply discard these.
and other research, but may have to be raised if very rapid pursuit or nystagmus is being recorded. The limit is set in degrees per second. An example of this command is: saccade_pursuit_fixup = 60 4.3.7 Fixation Updates Monitoring eye position or pupil size during fixations usually requires processing all samples produced by the tracker. This is acceptable for file data, but is expensive for real-time systems using data sent via the link.
• Saccade extension. This is intended to allow the saccade period to include the lower-velocity start and end of the saccadic period. This is usually disabled, as its effect is minor. • Internal constants. These MUST NOT be changed. 4.3.9 Sample Configurations The complete set of commands for the most useful tracker configurations is given below. The cognitive configuration is conservative, is less sensitive to noise and ignores most saccades smaller than 0.6°.
detection configurations into a new .INI file. Copy the original EDF file to the current EyeLink host directory (“C:\ELCL\EXE” by default). From the DOS command prompt, type: elcl -reparse {SOURCE_EDF} {DEST_EDF} -c {configuration_INI_FILE} where {SOURCE_EDF} is the name of the original EDF file; {DEST_EDF} is the name of the destination EDF file where the parsed data should be saved; {configuration_INI_FILE} the intended configuration file should be used.
Each sample may contain several data field, including: • Time of the sample (timestamp) in milliseconds • eye position data in gaze, HREF, or RAW data, monocular or binocular • Pupil size, monocular or binocular • Button or input port state bits All samples contain a timestamp, recorded in milliseconds. The time is measured from the time when the tracker software was started. This timestamp makes detection of missing samples possible, as well as simplifying processing of data.
line of sight (x,y) y x f (0,0) HREF Plane eye The (x,y) positions define a point in a plane at distance f (15000 units) from the eye. The HREF units are independent of system setup, display distance, and display resolution. The HREF coordinates are reported in integer values, with 260 or more units per visual degree. The (0, 0) point in the coordinate system is arbitrary, as the relationship between display positions and HREF coordinates changes as the subject's head moves.
display coordinates (usually pixels) which can be set in the EyeLink 1000 configuration file PHYSICAL.INI. The default EyeLink coordinates are those of a 1024 by 768 VGA display, with (0, 0) at the top left. The resolution data for gaze position data changes constantly depending on subject head position and point of gaze, and therefore is reported as a separate data type (see below).
Pupil size measurements are affected by up to 10% by pupil position, due to the optical distortion of the cornea of the eye, and camera-related factors. If research using pupil size is to be performed, the subject should not move their eyes during the trials. They can be presented with a fixation point with aural stimulus presentation, or a single stimulus position at display center may be used. It is also possible to counterbalance stimulus position during the experiment. 4.4.
EyeLink tracker, which timestamps the data and writes it to the EDF file. The application does not need precise time keeping, since link delays are usually very low (on the order of 1 or 2 milliseconds). Message events are used for two main purposes. They serve to precisely record the time of important events, such as display changes, subject responses, etc. They also record experiment-specific data, such as trial conditions. Message events consist of a millisecond timestamp, and the message data.
Eye-movement events are always labeled by which eye generated the event. If binocular data is recorded, a separate start and end event is generated for each eye. The time differences between eyes are very important for neurological analysis, for example. The main classes of data events are summarized below. Start events contain the time of the start of the eye-movement condition.
• The time of the first and last sample in the fixation • The eye that generated the event • Average HREF or gaze position data • Average pupil size • Gaze-data angular resolution All of this data may appear in the ENDFIX event that terminates the fixation. Only the starting data can appear in the STARTFIX event that initiates the fixation.
4.5.3.4 Saccades The EyeLink 1000 tracker's parser detects saccades by the velocity and acceleration of the eye movements. Because of variations in acceleration profiles, the onset and offset point of saccades can vary by one or two samples from "ideal" segmentation done by hand. Nonetheless, the saccadic data compiled by the parser is sufficient for most neuro-psychophysical research, including smooth pursuit.
In general, the saccadic amplitude will be slightly less than the distance between average position of the preceding and following fixations, as saccades do not include sub-threshold velocity parts of the eye movement that precede and follow the rapid phase. 4.5.3.5 Blinks The STARTBLINK and ENDBLINK events bracket parts of the eye-position data where the pupil size is very small, or the pupil in the camera image is missing or severely distorted by eyelid occlusion.
4.6.1 Sample Data The sample data written to the EDF file is controlled by the "file_sample_data" command, which is followed by a list of data types to include.
command. This is followed by a list of data types and options, selected from the list below: Keyword GAZE GAZERES HREF AREA VELOCITY STATUS FIXAVG NOSTART Effect includes display (gaze) position data.
file_event_filter = LEFT,RIGHT,FIXATION,BLINK,MESSAGE,BUTTON 4.7 EDF File Utilities A number of utility programs are included in the EyeLink 1000 package, to process and view EDF files. The utility EDF2ASC translates EDF files into text ASC files for processing with user applications. The EyeLink Data Viewer, an optional tool, allows displaying, filtering, and reporting output of EyeLink Data Files. Please check EyeLink Data Viewer User’s Manual for details. 4.
-e or -ns -nse -nmsg -neye -miss -setres -defres outputs event data only blocks output of start events blocks message event output outputs only non-eye events (for sample-only files) replaces missing data in ASC file with uses a fixed , resolution always uses a default , resolution if none in file 4.
• START events mark the beginning of each recording block, and END events mark the end of each block. The START events also specifies which eye’s data is present, and if samples, events, or both are present. • Data-specification lines follow each START event. These specify the type of data in samples and events in the block, and allow flexible data processing without prescanning the file. • All eye-movement samples and events occur between the START event and the matching END event.
• Monocular, with resolution
• MONOCULAR Corneal Reflection (CR) Samples "..." if no warning for sample first character is "I" if sample was interpolated second character is "C" if CR missing third character is "R" if CR recovery in progress • BINOCULAR Corneal Reflection (CR) Samples ".....
4.9.3 Event Line Formats Each type of event has its own line format. These use some of the data items listed below. Each line begins with a keyword (always in uppercase) and items are separated by one or more tabs or spaces.
4.9.3.5 Block Start & End • START • END
• SSACC • ESACC • ESACC The start of saccades are reported with a SSACC line, which can be eliminated with the EDF2ASC "-nse" option from the command line prompt or by enabling “Block Start Event Output” from the EDF2ASC converter GUI preference settings. The is "L" or "R", indicating the eye's data that produced the event.
4.9.4 Data-Specification Lines Immediately following a START line, several lines of data specifications may be present. These lines contain more extensive data than the START line about what data can be expected in the START...END block. These are most easily processed by creating a set of flags for each possible data option (left-eye events, right-eye samples, sample velocity, etc.), clearing these when the START line is encountered, and setting the appropriate flags when keywords ("LEFT", "VEL", etc.
4.10 Processing ASC Files An ASC file is a simple text file, and thus can be accessed by almost any programming language. The usual way to process the file is to read each line into a text buffer (at least 250 characters in size), and to scan the line as a series of tokens (non-space character groups). The first token in each line identifies what the line is: First character in first token # or ; or / * Digit (0..9) Letter (A..
5. System Care 5.1 Maintenance The EyeLink 1000 system should require little maintenance under normal use. If the IR mirror is dusted, it can be cleaned with the cleaning cloth we supplied. If the mirror is dirty (e.g., smudged with finger prints), please apply some cleaning solution we supplied and then wipe clean with the cloth. The forehead rest and the chinrest pad may be wiped with a damp cloth if cleaning is required.
6. Important Information 6.1 Safety 6.1.1 Eye Illumination Safety WARNING: Illuminators must only be connected to EyeLink CL camera, and only the supplied cables may be used. CAUTION: Use of a controls or adjustments or performance of procedures other than those specified herein may result in hazardous radiation exposure. CLASS 1 LED DEVICE IEC 60825-1 (Ed. 1.2:2001) The EyeLink CL illuminators are compliant with the IEC-60825-1 LED safety standard as a Class 1 LED device.
In addition to its invisible light output, the illuminators and heatsinks may become warm during operation. Therefore the illuminators should be mounted so as to minimize unnecessary skin contact. If illuminator mounting hardware is provided, be sure to follow the assembly instructions, as these may affect illuminator temperature. Ensure the illuminators are mounted so that air flow is not excessively restricted, as this could also increase the temperature.
6.2 Servicing Information WARNING: Changes or modifications to camera, illuminators, or cables not expressly approved by SR Research Ltd. could void the user’s warranty and authority to operate the equipment. This includes modification of cables, removal of ferrite chokes on cables, or opening cameras or illuminators. WARNING: Opening or modifying camera or illuminators, or power supply substitutions, will void the warranty and may affect the safety compliance of the system.
Re-mount the new illuminator , restore the routing of the illuminator cable(s), and reconnect the cable to the camera or illuminator. Reconnect the power supply, start the application software, and check to be sure the illuminator is producing proper output. If the mount allows the angle of the illuminator to be adjusted, it may be necessary to adjust the angle of the illuminator to provide the best illumination of the object of interest. 6.2.
6.2.4 Power Supply Replacement: WARNING: See the Specifications section for information on the power supply requirements. Use of a power supply with incorrect polarity, voltage, or other ratings may cause safety hazards, void the user’s warranty or damage system components. The EyeLink CL camera requires a power supply that is rated for 12V and 2A or higher. This supply must have a 2.5mm coaxial (“barrel”) power connector (5.5 × 2.5 × 9.5mm).
6.3 Limited Hardware Warranty SR Research Ltd. 5516 Main St., Osgoode, Ontario, Canada K0A 2W0 EyeLink 1000 Product Hardware– Limited Warranty SR Research Ltd. warrants this product to be free from defects in material and workmanship and agrees to remedy any such defect for a period as stated below from the date of original installation. EyeLink CL High Speed Camera – One (1) year parts and labor. EyeLink 1000 Illuminator Module – One (1) year parts and labor.
Support representative. For product repairs, please contact your sales representative for appropriate instructions. 6.4 Limited Software Warranty SR Research Ltd. warrants that the software disks and CD’s are free from defects in materials and workmanship under normal use for one (1) year from the date you receive them. This warranty is limited to the original owner and is not transferable. The entire liability of SR Research Ltd.
All other company and / or product names are trademarks of their respective manufacturers. Product design and specifications may change at any time without notice. Important Information © 2005-2008 SR Research Ltd.
7. Appendix A: Using the EyeLink 1000 Analog and Digital Output Card The EyeLink 1000 eye tracking system supports analog output and digital inputs and outputs via a DT334 card. The analog card supplies up to 8 channels of 16-bit resolution analog output, and 16 bits each of digital input and output. The analog outputs may be used to output up to 6 channels of eye and gaze position data for use by non-link and legacy applications.
Gaze: This is actual gaze position on the display screen. A calibration must be performed to obtain this measure. The EyeLink 1000 system offers integrated data recording and digital data transfer methods, which do not suffer from the timebase, resolution, and noise degradation inherent in analog systems. 7.
7.3.2 Connections to Analog Card The analog card is supplied with a connection cable and screw terminal connection board. Analog outputs and digital inputs and outputs are available from this card (see the document included with the screw terminal board for which terminals correspond to the analog outputs, digital inputs and outputs, and ground or +5V). It is up to each user to determine how to connect and use the analog output connections for their applications.
terminals on the connection board. Buttons and input ports are defined in BUTTONS.INI, with port addresses of 2 for port A, and 3 for port B. Here is an example of defining a button on port A, and assigning port B as the input port: create_button 8 2 0x01 1 input_data_ports 3 ; button 8, input A0, 0 is active ;; digital inputs B0..B7 as input port input_data_mask 0xFF ;; use all bits 7.4.1 Analog Data Output Assignments The EyeLink 1000 hardware outputs analog voltages on 3 channels.
ANALOG.INI). This allows operation with binocular data when few analog inputs are available, and when pupil size data is not required. The results of all combinations of configurations and monocular/binocular eye tracking modes are summarized in the table below, with X and Y representing horizontal and vertical position data, and P representing pupil size data. 7.4.2 Analog Data Types and Ranges Both gaze and HREF position data are available for analog output.
• For gaze position data, the data range is scaled to the display coordinates, which are 640 by 480 at startup, and may be changed via link commands. The data range setting is -0.2 to 1.2, allowing 20% extra range for fixations that map to outside the display. This extra data range allows for slippage or for identification of fixations outside the display. Scaling to recover gaze position data is more complex, as the numerical value is partially dependent on the display coordinates.
recording of a single eye-position sample. This would appear as a "step" artifact in rapidly-changing eye-position data, such as saccades or pursuit. 7.6.1 Strobe Data Input The best time base method is to use the EyeLink 1000 analog output strobe, which is assigned to digital output D7 on the analog card connection board.
