Dalsa Z-Trak2 2K Series User Manual page 25

Teledyne Vision Solutions
Standoff distance
The standoff distance (also known as the clearance distance) is the minimum distance from the laser exit window
where measurements can be made. This distance is model dependent and cannot be changed by users. Any
measured point located between the laser exit window and the standoff distance will return an invalid code.
Z range (Measurement Range)
The Z range is the maximum height, in world measurement units, that the 3D sensor can measure. The Z range,
also called depth of field (DOF), is model dependent and factory calibrated, and cannot be changed by users.
The start of the Z range (the 0 value) is the farthest point from the laser exit window; the end (max Z value) is the
closest to the exit window and represents the highest value that the sensor can measure. In the figure above, the
Z range extends from the bottom to the top.
Field of view (FOV), Near-FOV (NFOV), Mid-FOV(MFOV), Far-FOV (FFOV)
The field of view is the section of the X-axis where Z measurements can be made. Its size depends on the
distance from the 3D sensor; the FOV is larger at the start of the measurement range than at its end. This implies
that the resolution in X varies with the distance from the profiler.
The FOV at the start of the measurement range is the far-FOV; it is the largest section where measurements can
be made.
The FOV at the end of the measurement range is the near-FOV; it is the smallest measurement section, closest
to the device.
The mid-FOV provides an indication of the size of the measurement section midway between the near-FOV and
far-FOV.
Note that the laser line extends beyond the FOV; however, the factory calibration ensures that Z measurements
can take place in the entire trapezoidal region delimited by the FOV in the XZ-plane (see measurement area
definition).
Measurement area
The measurement area is the trapezoidal region in the XZ-plane that is delimited by the FOV, from the near-FOV
to the far-FOV. It is the largest region in which measurements can be made. The measurement area is
determined at the time of factory calibration and cannot be changed by users. In the figure above, the
measurement area is represented by the black trapezoid.
Measurement AOI (M-AOI)
The measurement area-of-interest, called measurement AOI, is an area equal to or smaller than the
measurement area, where the measurements are to be made. The measurement AOI can be changed by users:
a smaller measurement AOI means that a larger number of profiles can be processed for a given amount of time,
thereby increasing scanning rate. In the figure above, the measurement AOI is depicted by the blue dash
trapezoid.
Working range, Working distance
The working range is the interval between the nearest and farthest distances from the laser exit window where
measurements are made. The interval corresponds to the height of the measurement AOI; the starting position of
the measurement AOI is also called the working distance. The working range varies with the size and the position
of the measurement AOI (see figure above).
Theory of Operation and Definitions • 17
Z-Trak Family of 3D Sensors