Chapter
3
Reference Manual
Ruler E
Configuring the Ruler
The position of the first and last pixel defining this width can be computed with a resolu-
tion of one pixel.
½
-pixel position:
The center of the light peak can be computed as the mid-position of the
first and last pixel that represent the peak. If the width of this group consists of an even
number of ones, the mid-position will fall between two pixel centers. Thus the impact
position will have a resolution of half a pixel.
¼
-pixel position:
Two peak-widths can be computed using two different thresholds. For
each width the mid-positions are computed with a resolution of half a pixel. The average of
the two mid-positions is then computed giving a resolution of a quarter of a pixel.
Multiple light peaks
If several light peaks are above the threshold at the same sensor column the first peak
found in the search direction is used to represent the impact position of the laser line. This
may not be true and will in this case yield an incorrect range measurement.
Figure 3.7 – A too low threshold may detect multiple light peaks
In this case either the false peak must be suppressed or the threshold must be altered (as
in following figure.
Figure 3.8 – Altering the threshold to remove false peaks
In the case that the true light peak (the laser) is the first along the search order the correct
range value will be computed.
Intensity
False laser peak
Threshold
Sensor row
ROI end
ROI start
Sensor row
ROI end
ROI start
Intensity
Threshold
False laser peak
Sensor row
ROI end
ROI start
Sensor row
ROI end
ROI start
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