Operation Manual

Product Reference Guide 287
Appendix B
Aimer Calibration
The Scan Modules in the GFS4400 series
contain a laser-based aiming system
consisting of four corner dots and a center
crosshair pattern that helps define the
reading volume. The center cross location in
the imager's Field Of View (FOV) is
recorded and logged in the system's non-
volatile memory (calibration process), and
facilitates the Central Code Only operation.
Central Code Only is a programmable
mode of operation which controls the scan
module's ability to decode labels only when
they are close to the center of the aiming
pattern. This allows the reader to accurately target a particular label when there are multiple bar
codes placed close together, such as on a pick sheet.
The imager's sensor has a resolution of WVGA (752H x 480V) and typical 'aimer coordinates'
will be in the realm of 03350235, which translates to a location 335H x 235V in the FOV.
These coordinate values will change slightly from scanner to scanner, and are also dependent
upon Depth of Field (DOF) when calibration is performed.
Aimer calibration can be done using simple Command
String
s within the reader's Service Mode of operation
(described in
"Software Configuration Strings" starting
on page 217). Recalibration of the reader's aimer can
be done if it is believed that performance can be
improved by calibrating at a specific depth of field (a
recalibration), or if
some special application would
benefit by custom configuring and writing in
'phantom coordinates'
1
.
Below are the commands available for aimer
calibration, followed by examples.
Fx - Aiming Auto Calibration. The reader
will switch on the laser aimer, determine the
coordinates of the center cross, and store into the factory non-volatile memory area (Aimer
Calibration).
Fa - Aiming Read Coordinates. Returns th
e coordinates of the center of the aiming pattern
or the custom coordinates set from user defined (FA).
1. Phantom Coordinates - aimer coordinates custom programmed into a scanner's Field of View location rather than at
the aimer's center crosshairs.