SICK Ranger3

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ROI start
The laser line will produce a distinct light peak distributed over a number of pixels along
the sensor column. The center of this peak will be defined as the impact position of the
laser line on that sensor column, which is the range value.
8.7.2 Measurement method
The default algorithm in Ranger3 is called Hi3D. It measures the impact position using
a high-resolution peak fitting algorithm based on the pixels in a window around the
extracted intensity peak position. The size of the window is defined by the WAM size
setting.
This method measures range with a resolution of 1/16
th
pixel.
Profiling close to ROI edges
The window around maximum is found and extracted at the maximum (first saturated)
pixel position in a column. This is true for the normal GlobalMax search mode, and "first"
can be lowest (SearchDirection Standard) or highest (SearchDirection Reverse) in the
region of interest. Around this position, +/- 3, 7 or 15 pixels are extracted for the WAM
window. The number of pixels are dependent on the setting of the WAM Size parameter.
To be able to find a true peak position, it is necessary to have data on both the up and
down slope around the peak. If the found peak position for the extraction is such that
the WAM window extends outside of the defined region of interest, part of the WAM
window is undefined. This makes it impossible to calculate a true peak position.
Figure 20: Laser line close to ROI edges
The implementation of the ROCC
2)
logic is such that the actual content of an undefined
WAM window portion may depend on the column position. Therefore, it is typical that
visible artefacts first are visible in a pattern repeating every 80th column of the 3D
data. Zooming in on the data it is possible to se artefacts in more detail, with jumps in
the data at 80-column intervals.
Figure 21: Missing data of an undefined WAM window
The solution to this problem, is to ensure that the WAM window is extracted within
the region of interest, i.e. that the peak position is within half the WAM Size from the
border of the region of interest. Mitigation includes reducing the WAM Size and reducing
exposure/saturation to avoid the peak position to be too close to the border.
8.7.2.1 WAM size
The size of Window Around Maximum (WAM) is used for high-resolution peak fitting. The
selected value should correspond to the laser peak width on the sensor.
2)
Rapid On-Chip Calculation
CONFIGURATION 8
8020774/1D7Q/2022-03 | SICK O P E R A T I N G I N S T R U C T I O N S | Ranger3
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Subject to change without notice