Chapter 9
Full Frame Readout
59
EAR99
Technology
Subject
to
Restrictions
Contained
on
the
Cover
Page.
9.2.1.3.1
Normal
illustrates the timing diagram for Readout Per Trigger mode combined with
Normal shutter mode.
Figure 9-12: Full Frame Timing Diagram: Readout Per Trigger, Normal
When a trigger pulse has been received, Lansis opens the active shutter for the
programmed exposure time, t
exp
.
Once the exposure is complete, the shutter is closed, and the CCD array is read out.
Because a shutter requires a finite length of time to fully open, the trigger pulse from
the experiment must precede the start of data acquisition by at least this length of time.
If it does not, the shutter may not be completely open throughout the duration of the
desired data acquisition, and data acquisition may even be missed completely.
Since the amount of time from initialization of the experiment to the first trigger pulse is
not fixed, an accurate background subtraction may not be possible for the first readout,
nor for all subsequent shots since the trigger is external, is not synchronous with the
camera, and therefore not synchronous with the cleaning cycle.
**
If Enabled
EXPOSE
TRIGGER
t
O
t
C
SHUTTER
Normal
Wait For
Trigger
WFT
t
O
READOUT
t
R
ACQUIRE
Pgm’d
Cleans
Clean
Until
Trigger
**
Clean
Until
Trigger
**
t
exp
44
11
-0
17
4
_
0
0
3
2
