Northern Digital Polaris Vicra User Manual page 94

Illuminator Ring
The illuminator ring is a ring of IR light emitting diodes that surround the sensor lenses on the
Position Sensor. These flood the area in front of the Position Sensor with IR light, which is reflected
back to the Position Sensor by the passive markers.
Line Separation
To determine the position of an IR source, the Position Sensor calculates a line between the source
of IR and each sensor. The line separation is the distance between these two lines where they cross.
Local Coordinate System
A local coordinate system is a coordinate system assigned to a specific tool or rigid body.
Maximum 3D Error
Maximum 3D error applies to individual markers. It specifies, in the tool definition file, the
maximum allowable difference between the measured and expected location of a marker on a tool or
rigid body.
Maximum Marker Angle
Maximum marker angle is used to determine if a marker will be used in the calculation of a rigid
body or tool. If the marker is determined to be farther off-angle to the Position Sensor than the
maximum marker angle, this data is not used to determine the rigid body or tool.
Passive Marker
A passive marker is a retro-reflective passive sphere that reflects IR light emitted by the Position
Sensor.
Pivoting
Pivoting is a procedure (of rotating a tool about its tip) used to determine the tool tip offset.
Position Sensor
The Position Sensor is the component of the Polaris Vicra System that provides a source of IR light
for passive markers, collects marker position data from both active and passive markers, calculates
tool transformations, and sends the results to the host computer.
Quaternion
A quaternion is a compact representation of rotations, or correspondingly, orientations in 3D space
(rather than having to use orthogonal matrices).
Reference Tool
A reference tool is a tool or rigid body whose local coordinate system is used as a frame of reference
in which other tools are reported/measured.
82 Polaris Vicra User Guide - Revision 2