Long Range Mount Installation
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2005-2010 SR Research Ltd.
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The eye tracker can be easily removed from the MEG room when not in use, for either space
conservation reasons or to use it in a behavioural lab. Apart from requiring a Host PC in the
vicinity, setup and take down are fast with only minimal adjustment required between
subjects. Once configured, simply place the eye tracker in the room as appropriate when eye
tracking is desired, plug in its two DC power leads and its single fiber optic lead, power up the
system and begin recording.
There are three mounting options that have proven useful for MEG at the current time:
1.
Desktop Base.
The Mounting Bar can be attached to a Desktop Base such as in
Figure
7-1
. To get a good view of the eye, the base is typically placed on a shelf bridging the
participant’s lap. This allows the eye tracker to be at about 60 cm from the observer
with CTF and Elekta Neuromag MEG systems, making for an excellent eye-tracking
signal.
Once the mounting position has been determined, users may wish to create a wooden
pedestal to rest the mount on. It is important that the mount be solid, as any vibration
will degrade eye movement recording and act as a potential noise source. For this
reason the Desktop Base should never be placed on any construction making contact
with the participant or their chair in order to prevent the subject from introducing any
form of vibration to the apparatus.
2.
Screen Mount.
A Screen Mount is designed to clamp to the bottom of a screen frame
such as that supplied with Elekta Neuromag systems (see left side of Figure 7-10) or
often used with 4D systems (see right side of Figure 7-10 for an example of such a
custom-built screen). The top of the mount has the universal ball joint found on the
EyeLink 1000 Desktop Base of Figure 7-1. Eye-to-camera distance in this configuration
is typically greater than 90 cm.
The Screen Mount typically clamps onto the bottom of a screen frame. Mounts are
available for narrow (37 mm width) or wide (75 mm) screen frames. An optional rubber
bumper takes up a further 9 mm of this gap. The bottom of the Camera Head and
Illuminator are a minimum of 150 mm above where the clamp mounts onto the screen
with a maximum height of 395 mm.
3.
Tripod.
The Mounting Bar can be removed and attached to a MEG-friendly tripod (not
supplied) using the plastic Tripod Adapter, and the tripod placed at the participant’s
feet in front of, or just below a projection screen. The tripod is used to adjust the view of
the camera by moving the illuminator and camera head together. Typical viewing
distances for such a setup are 90 cm and will work well with Elekta Neuromag and 4D
systems because the screens are rather high in the field of view and far removed from
the subject.
