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Chapter
6
Operating Instructions
CLV490 Bar Code Scanner
6-12
©
SICK AG · Division Auto Ident · Germany · All rights reserved
8009993/RA61/2007-07-20
Operation
The time at which focusing occurs relative to the reading pulse can be selected for both
types of focus control.
Autofocus
Condition: Reading from above
•
Minimum distance:
Relative to its surroundings, the object is always located at the shortest distance from
the CLV490. Example: object positioned directly on the conveyor belt without a
container (tray, etc.) or interfering side boundaries
Condition: only
one object
in the reading field during the reading interval.
•
Differential background:
The background can be closer to the CLV490 than the object.
Example: object in a container on the conveyor belt; the container wall is higher than
the object (closer to the CLV490).
Condition: only
one object
in the reading field during the reading interval.
•
Differential background and tracking:
Same as the "Differential background" function, except that in each reading pulse
more
than one object
can be located in the reading field at the same time. On the basis of
the detected distances, the CLV490 assigns the required focus positions in its internal
focus list to the objects and organizes the objects using a continuous increment in its
object list. In this way, scanned bar-code information can be uniquely assigned to the
individual objects. This is only available in the reading mode "Tracking" (internal tracking
or reading mode "OTS trigger"), not in "Object polling" mode (one object only) of start/
stop mode. For more detailed information, see also
(controlled by Increment), Page 6-27
Explanation
Background teach-in:
For autofocus modes "Differential background" and "Differential background and tracking",
the CLV490 can also teach in the ambient background in its area of view (e.g. if interfering
objects in the conveyor system project into the defined autofocus area) in order to improve
the evaluation of the current distance profile. When doing so, the CLV490 adjusts – among
other things – the measured background by 100 mm (3.9 in) in its direction to compensate
any measurement inaccuracies.
The default background at a distance of 2,200 mm (86.7 in) is used in all other cases and,
if necessary, the autofocus area is limited by means of the appropriate parameters. In this
Action
Settings in CLV-Setup
Activate autofocus
–
or
–
Ö
R
EADING
C
ONFIGURATION
tab
Ö
F
OCUS
C
ONTROL
section
– Autofocus
Activate focus position switch-
over (event-controlled)
(selecting trigger source)
Ö
R
EADING
C
ONFIGURATION
tab
Ö
F
OCUS
C
ONTROL
section
– Inputs/Serial
or
– Timer
Ö
T
IMER
or
– Static/No trigger
Oscillating mirror:
– additionally: Oscillating mirror extrema
Table 6-5: Guide: Selecting the focus control mode
c) Parameterizing focus control
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