Operating Instructions
Chapter
3
CLV 490 Bar Code Scanner
8 008 796/0000/25-06-2002
©
SICK AG · Division Auto Ident · Germany · All rights reserved
3-7
Product description
3.2.2
Event-controlled dynamic focus control
As an alternative to the autofocus function, the CLV can switch its focus position in response
to certain events and thus dynamically cover a large reading range. A maximum of eight rea-
ding ranges can be defined as distance configurations for this purpose and approached
consecutively in reading mode (see
).
The switch over takes place in response to changes in the object distance (with reads from
above: object height detection). The trigger source for the switchover is a signal combination
at the "IN 0 ... IN 4" switching inputs, a command on the host interface/terminal interface or
the integrated timer (e. g. for search mode). Additional in the case of the line scanner with
oscillating mirror also the oscillating mirror reversal points. The distance configurations are
assigned to the switchover sequence by means of a programmable assignment table. The
distance measurement of the autofocus function can be additionally used to define the di-
stance configurations.
3.2.3
Scan procedure variants
Line scanner (standard device)
Generates a scan line; due to the V-principle of the beam generation, the reading field height
(the useful length of the scan line for evaluation purposes) is dependent on the reading
distance.
Line scanner with oscillating mirror
The oscillating mirror also deflects the scan line perpendicularly to the scan direction at both
sides around the neutral position with a low oscillating frequency. As a result, the CLV can
also scan larger areas for bar codes. Due to the V-principle of beam generation, the reading
field height is dependent on the reading distance.
In addition to parking (fixed position) and simple deflection with maximum amplitude, opti-
mized oscillating mirror functions are also available:
•
Oscillating with variable deflection amplitude per distance configuration
•
One-Shot: one-off, defined deflection per reading pulse (forward and return phase)
Fig. 3-4:
Dynamic focus control: classification of the reading range in distance configurations
1
2
3
5
8
4
6
7
Reading
field height
Focus
position
Reading distance
Focus position
Reading distance
DC = Distance Configuration
DC 1
DC 3
DC 4
DC 6
DC 7
DC 8
DC 2
DC 5
