The filters can be combined without restrictions. If several filters are active, then the
filters are applied sequentially to the results of the preceding filter. The processing
sequence is as follows:
•
Scan range filter
•
Edge filter
•
Median filter
•
Mean filter
The active filter functions affect the output measured values. It is not possible to recal‐
culate the original measured values from the filtered output values. For this reason, cer‐
tain combinations of filters might not be advisable.
A particularly effective way to reduce the data in a scan is to restrict the scan range
(reducing the measurement points). A good way of reducing data in multiple scans is to
use the mean filter (reducing the event rate) or, alternatively, to select a higher output
interval.
3.5.8.1
Scan range filter
The scan range filter is used to restrict the angular range output per scan.
The maximum range is set to 70° by default. This produces 841 measurement points.
The range can be restricted by increasing the start angle (default setting = 55°) or
reducing the stop angle (default = 125°). Please note that the angle beam is defined
orthogonally in relation to the front at 90° and the direction of rotation of the device is
set to counterclockwise,
.
The minimum difference between start angle and stop angle is 1/12°; this is equiva‐
lent to the output of a single measurement point. It is not possible to output multiple
scan ranges (e.g., 55° ... 70° and 90° ... 110°).
3.5.8.2
Edge filter
The edge filter eliminates erroneous or extreme distance values at edges. These arise
as a result of laser light, which partly hits an object in the foreground and partly hits a
more distant object, or due to too little light remission at the object itself,
object surfaces on the measurement", page 19
. The filter evaluates the difference in
distance between adjacent points.
When the edge filter is activated, the device sets a distance value of 0 at each edge
(values in
bold
in the table).
Table 4: Example: Measured values with and without edge filter
Angle (distance values in mm)
Scan
1
2
3
4
5
6
7
…
1, not filtered
0
750
1145
1150
1147
1500
0
…
1, filtered
0
0
1145
1150
1147
0
0
…
The edge filter enables points to be entirely suppressed at the outer edges of the
object. In this case, the width of an object is detected by up to 2× angular resolution too
narrow.
3.5.8.3
Median filter
This filter is suitable for excluding individual outliers in the distance values.
The values included in the calculation are defined using a 1 x 3 matrix:
3 measured values, consisting of the distance values of a point and its two adjacent
points in the scan, are sorted by size.
PRODUCT DESCRIPTION
3
8023202/16S6/2020-01-24 | SICK
O P E R A T I N G I N S T R U C T I O N S | LMS4400/LMS4500
21
Subject to change without notice
