5-16
SE4400 Integration Guide
Motor Control
The SE4400’s lens system can be dynamically set to near or far focus positions:
•
The near focus allows the SE4400 to focus on objects that are about five inches
away.
•
The far focus allows the SE4400 to focus on objects that are about nine inches
away. This improves distance picture taking capability.
•
Toggle mode uses the superset of the two focus positions, allowing the SE4400 to
achieve excellent working range across a variety of bar code densities.
describes the focus position control.
Once instructed, the motor moves and settles within 20 ms, meaning that for each frame in
which the focus was changed the exposure time cannot exceed a frame time minus 20 ms.
If a focus position is forced to near or far, the exposure time can be as large as a frame time
as long as the motor is given 20 ms to settle from the time the focus position is forced to
the time the first image exposure begins. Even if toggle mode is not used, any change to
the focus position should occur at the beginning of the frame to allow the motor to settle
before the next exposure.
Exposure & Gain Control
In Mode 3, the exposure time is the period that EXSFT is held low. In Mode 1, the exposure
time is set in line times to I
2
C register 151d. For example, in
, a value of 157
results in an exposure time of 157 x 764
T
= 10 ms. Once set, the exposure value occurs
during the next frame, which is read out during the frame after that. The SE4400 starts in
Table 5-4. Focus Control Definitions
FOCUS_CTRL1 FOCUS_CTRL2
Operation
Comments
0
0
Motor completely OFF
Motor not held in either
position.
0
1
Far Focus Position Selected
Motor forced into far position.
1
0
Near Focus Position Selected
Motor forced into near position.
1
1
Toggle Mode
Motor toggles between near
and far positions on each rising
edge of EXSFT.
Summary of Contents for Symbol SE4400
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