B.2. Components of the Eyetracking system

Figure B.3. Eyetracking Hardware.

Eyetracking Hardware.

The physical hardware for eyetracking consists of multiple parts that are split between the Control room and the Equipment Backroom. An image of the components is shown in (Figure B.3).

B.2.1. Hardware

B.2.1.1. Control Room

Hardware in the Control Room include:

  1. Eyetrack PC, monitor, keyboard and mouse: This is the control centre for the software that drives the eyetracker itself. This computer and the Eyetrack software on it need to be running when we want to acquire Eyetracking data.
  2. Stimulus display: this black and white CRT monitor displays a copy of the stimulus output as seen by the participant in the scanner.
  3. Eye display: this black and white CRT monitor shows the output of the eye camera in the equipment room – the pupil of the eye will show up as a white circle if the camera is focussed and position correctly.
  4. ASL Control Unit: This is the white box that sits on top of the Stimulus and eye displays. It controls the communication between the PC and the eyetracker optics in the equipment room.

B.2.1.2. Equipment Backroom

Hardware in the Equipment BackRoom include:

  1. Long range optics box: This box houses a number of components.
    1. A powerful light source: this is projected onto the eye to cause the pupil reflection. Of course we don’t want a really bright light constantly shining on the participant’s eye, so the light is projected through an infrared filter. Hence only infrared light reaches the eye and cannot be physical perceived.
    2. A camera to track the eye: this video camera takes images of the eye at a 50/60Hz frequency. This information is passed out to the LCD camera display (below) and the ASL Control unit and Eye display in the control room.
    3. Alignment mirrors: a set of mirrors is used to align the beam of infrared light to the capture path of the camera optics (so that the camera is 'looking where the light is shining' so to speak)
  2. An LCD camera display: this screen shows the output of the eye camera (in the long range optics box) in the equipment room so that the user can align the camera on the participant’s pupil during setup.
  3. A power supply: the power supply to the long range optics box and LCD screen.

B.2.2. Software

All software controlling this system is housed on the Eyetrack PC in the control room. The software package used is called Eyetrack 6000 and is launched from the Eyetrack PC in the control room.