LiveTrack AV for fMRI installation manual
Version R02
8
How it works
Image Capture
The 940nm LED light is embedded in the camera housing. The short distance between the lens
and LED is chosen in order to avoid undesired shadowing effects.
The image of the eye formed by the lens is captured by a built-in CMOS image sensor.
Image Processing
The LiveTrack device takes the frame and subjects it to on-board image processing to locate the
Pupil and glint (the glint is a first Purkinje Image).
USB interfaces
The USB connection is configurable, and provides three different interfaces to the host
computer over the single USB lead. It is compatible with all major operating systems.
1)
Mass storage interface (USB MSD). This is used for initial configuration of the eye-
tracker and for system upgrades.
2)
HID class interface (USB HID). The LiveTrack emulates a Human Interface Device and
requires no additional driver
3)
Video feed (USB UVC). Used to align the camera to the subject.
By default HID and UVC interfaces are both turn on. The MSD interface can be access by pressing
button through the little hole on the side of the LiveTrack DSP box.
Synchronisation
LiveTrack has a trigger input, which should be connected to a suitable output of the stimulus
generator. This enables the eye-tracking results to be synchronised perfectly with the
experiment.
