7.2.7 Extending DOF Using External Image Settings Selection
Sequence (Input Select) for Liquid Lens Models
For Liquid Lens models, multiple Image Acquisition Settings can be configured and enabled
externally through a distance sensor to extend the reader's depth of field. The specific Image
Acquisition Setting Sequence is selected prior to the reading phase so that only the correct
setting (or group of settings) will be applied to the entire reading phase.
When only two Image Acquisition Settings are used to extend DOF, (one in each sequence),
this effectively allows switching DOF while keeping the lens refocusing delay outside the
reading phase.
This feature is recommended for high speed applications.
Example:
Read a 15 mil Data Matrix ECC 200 code covering a range from 140 to 320 mm at an
application speed of 1 m/s. The reading distance range is too long to be covered by a single
acquisition setting, so two acquisition settings could be used in which the first has a Reading
Distance of 195 mm and is assigned to Image Settings #1, and the second has a Reading
Distance of 300 mm and is assigned to Image Settings #2.
By assigning the Image Settings Selection to External, a proximity sensor (i.e. S3Z)
mounted at least 150 ms before the Acquisition Trigger and connected to an input (i.e.
Input 2), the correct DOF can be selected by enabling the correct sequence.
As an example, for a conveyor speed of 1 meter/second the Activation Event Trigger (Input
2 sensor) must be placed at least 150 mm before the reading phase start (Ext. Trigger).
The proximity sensor must be calibrated to trigger on packs in the near zone (140-215 mm)
and therefore select the Sequence with Image Settings #1 (the Image Acquistion Setting
relative to the 195 mm Reading Distance). Packs farther away do not trigger the proximity
sensor and so the Sequence with Image Settings #2 is selected with the Image Acquistion
Setting relative to the 300 mm Reading Distance.
The settings overlap in the range 210-220 mm and can be read by either one.
In this way the effective reading DOF covers the 140 -320 mm distance.
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