Computing Resources

Instructions for Use of Eye Tracker

There is one eye tracker system for use in either the 1.5T or 3T scanner. Move eye tracker system cart into the control room you are using. The carrying case containing the camera with mount, interface, power pack and some cables should be on the cart along with the computer, keyboard and mouse. A monitor already in place in each control room is used with this system so no monitor is needed on the cart.

Computer Connections

Refer to the connection diagram along with these instructions.

  1. Unwind several feet of power cord from the outlet strip on the front of the computer cart. Position the cart under the counter,  just to the right of the equipment cabinet with the back of the computer facing out. Plug the power cord into any convenient outlet.
  2. Six cables are bundled together at the back of the computer cart. The six mating connections are in the equipment cabinet, on the center shelf at the right side. Join all six cables together. They are:
    1. HD15 VGA for the primary PC monitor is labeled "1" on both connectors.
    2. HD15 VGA for the secondary monitor (the projector) is labeled "2" on both connectors. This display is used to calibrate the eye tracker.
    3. DB9 serial connection labeled "3". This joins COM1 of the eye tracker computer to COM2 of the paradigm PC. This allows the paradigm PC to control the Viewpoint software on the eye tracker computer.
    4. ST terminated orange fiber-optic cable joins to the long fiber that goes into the scan room and connects to the Video Interface box. Insert the tip of the ST connector and rotate it until the key lines up. Then insert it fully and rotate the locking ring. Handle all fiber-optics with care – the ceramic tip is easily broken; the cable contains glass fiber.
    5. RJ45 network cable is connected so files can be moved off the eye tracker computer via local network.
    6. Coaxial cable with BNC connector feeds eye camera video to the RCA Video In of the DVD Recorder in the equipment cabinet. This allows the eye camera to be recorded on DVD, if desired and is used when aiming the eye camera.
  3. Power on the computer by pressing the button on right, front of computer. This is most easily reached from the left since you are working from the back. Power on DVD Recorder in the equipment cabinet and in 3T room set to channel L3, and in 1.5T room to L1.

Camera Connections

All camera components are stored in the padded carrying case. Refer to the connection diagram along with these instructions.

  1. Preparation before entering the scan room
    1. Connect the cable from the power pack to the power connector of the Video Interface box.
    2. Inspect the camera carefully - be sure it is pressed all the way onto the connector at the end of the gooseneck. The camera is removable but should not be removed except for maintenance.
    3. Loosen the plastic wing nuts on the goosneck base slightly so the keyed base projects from the mount.
  2. Bring in the Interface box and power pack
    1. Do not walk close to the scanner - keep close to the wall - carry in the Interface Box and power pack only. 
    2. These components contain ferrous materials and will be pulled into the magnet if close enough.
    3. In 3T the Interface is placed on the same wall as the door, halfway down. In the 1.5T it is placed on the right side wall just past the coil storage cabinet.
    4. Connect the power pack tether snap to the eye bolt in the wall just below the electrical receptacle.
    5. Press the Interface box firmly onto the mating Velcro pad on the gray plastic wiremold.
    6. Plug the power pack into the receptacle.
    7. Plug the fiber-optic cable into the mating jack on the Interface box.
    8. These components are now secure. Do not remove them while a subject is present in the scan room.
  3. Take the camera into the scan room - there are no ferrous parts - it does not pull toward the magnet.
    1. Insert its keyed base into the widened slot at the foot end of the scanner table so the cable exits in toward the foot of the table. The preferred side is the patient's left since this keeps the camera cable clear of the head coil cable.
    2. Slide the camera mount to a position just below the head coil. Adjust the gooseneck to place the camera approximately in position for eye tracking. Lay the camera power/video cable along the table slot to the foot end of the table. There are small wedges that can be slid into the table slot to hold the cable in position.
    3. Connect the camera power/video cable to the interface box.

Camera Setup

On the eye tracker computer, start up the ViewPoint software. If all is well, the Eye Camera window should display live video from the camera. If not recheck all connections.

Aim

Make sure the projector is on and select the NTSC Video source. In 1.5T use the Mac Projector Control program, select NTSC button.  In 3T use the Epson IR remote control, select Video button in the lower covered section. The eye camera will be projected onto the screen in the magnet bore for use in aiming the camera. Position the subject and stabilize the head as securely as possible - this is very important. Head motion is a major problem during eye tracking. With the head coil in place, position the camera so the eye is centered on the screen and almost fills the screen left to right. Refer to the Viewpoint manual section 4.2 for more on camera setup and 4.4 for instructions on thresholding. Camera position influences ligthing of the eye. Check that the software can properly detect the pupil - adjust camera if necessary.

Calibrate

When the subject is advanced to the scan position, calibrate the eye tracker. Instruct the subject to watch the targets as they appear on the screen. Tell them to fixate on each target until the next target begins to appear. In 1.5T use Mac Projector Control program, select the Computer button and then set the Projecter Video Switch in the equipment cabinet to "User2", In 3T use the Epson remote control, select "Computer2" button in the lower covered section. In the Viewpoint software, Stimuli menu, select Stimulus Window Properties, Full Screen Monitor 2 so the calibration window is displayed on the secondary monitor (the projector). Follow the Calibration instructions (section 4.5 and chapter 6) in the Viewpoint manual.

Present Stimulus

After successful calibration, switch the projector to display your stimulus computer. In 1.5T set Projector Video switch to "PC" or "Mac" position, in 3T use the Epson remote control to select "Computer 1".


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