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46 ST-133 Controller Manual Version 3.B
Shutter (Normal)
Open Close Open Close Open Close
Read Read Read
Shutter (Preopen)
Open Close Open
Close
Open Close
External Sync
(negative polarity shown)
First wait
and exposure
Data
stored
Second wait
and exposure
Third wait
and exposure
Data
stored
Data
stored
t
exp
t
c
t
R
t
w1
NOTSCAN
Figure 13. Timing Diagram for the External Sync Mode
External Sync with Continuous Cleans Timing
Another timing mode available with an ST-133 controller is called Continuous Cleans. In
addition to the standard "cleaning" of the array, which occurs after the controller is
enabled, Continuous Cleans will remove any charge from the array until the moment the
External Sync pulse is received.
Shutter opens
Shutter remains open
for preprogrammed
exposure time
System waits while
shutter closes
Shutter opens
CCD is continuously
cleaned until External Sync
pulse is received
(shutter preopen)
(shutter normal)
CCD is continuously
cleaned until External Sync
pulse is received
Figure 14. Continuous Cleans Operation Flow Chart
Once the External Sync pulse is received, cleaning of the array stops as soon as the
current row is shifted, and frame collection begins. With Normal Shutter operation the
shutter is opened for the set exposure time. With PreOpen Shutter operation the shutter is
open during the continuous cleaning, and once the External Sync pulse is received the
shutter remains open for the set exposure time, then closes. If the vertical rows are shifted
midway when the External Sync pulse arrives, the pulse is saved until the row shifting is