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4
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.
7.7.2
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 set by the
WAMSize
parame‐
ter.
This method measures range with a resolution of 1/16
th
pixel.
7.7.3
Detection threshold
The parameter
DetectionThreshold
defines the minimum reflectance signal that can be
detected as a peak position. Ideally, this parameter is set to a value that is higher than
the amplitude of the noise, but still low enough to detect the laser signal, see the figure
below. If
DetectionThreshold
is too low, noise will be registered as laser peaks. This will
result in bad image quality. If
DetectionThreshold
is too high, not all laser peaks will be
registered. This will result in an image where some parts are missing.
Intensity
1
ROI start
4
ROI end
3
Sensor row
2
DetectionThreshold
6
6
5
Figure 12: Analog signal with noise
1
Intensity
2
Sensor row
3
ROI end
4
ROI start
5
Detected peak
6
Not detected peaks
7.8
3D data formats
The 3D data is delivered with 4 subpixel bits resolution. The data can be represented
with 12 or 16 bits. 12 bits allows a higher scan rate given the limitations of the Gigabit
Ethernet link. For 12 bits a maximum region height of 256 rows can be represented.
Any data outside of this is clipped/limited to the maximum value.
The pixel value 0 is dedicated to represent missing data, i.e. that no valid peak was
found. This means that the lowest value possible is 0.0625 (1/16th).
The coordinate system of the data is independent of the region position. That is, the
value 0.0625 always represents a position 1/16th of a pixel from the start of the
region. If a buffer is saved to file, the offsetY information is stored in the XML descrip‐
tion so that the actual position on the sensor can be calculated.
CONFIGURATION
7
8020774/14IM/2019-07 | SICK
O P E R A T I N G I N S T R U C T I O N S | Ranger3
29
Subject to change without notice