Teledyne Princeton Instruments PI-MTE, System Manual

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64 PI-MTE System Manual Issue 6
Figure 6-6: Flowchart: Continuous Cleans Operation
Once the External Sync pulse trigger edge is received, cleaning of the array stops as
soon as the current row is shifted, and frame collection begins: a delay time of up to
one row shift can be expected. 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 trigger edge 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 trigger edge arrives, the pulse is saved
until the row shifting is completed, to prevent the CCD from getting out of step. As
expected, the response latency is on the order of one vertical shift time, from
1 - 30

sec depending on the array. This latency does not prevent the incoming signal
from being detected, since photo generated electrons are still collected over the entire
active area. However, if the signal arrival is coincident with the vertical shifting, image
smearing of up to one pixel is possible. The amount of smearing is a function of the
signal duration compared to the single vertical shift time.
Figure 6-7 illustrates the same timing diagram as Figure 6-5 with the addition of
Continuous Cleans information, which is indicated by shaded areas labeled CC.
Continuous Cleans are additional clean cycles defined by the same parameter values as
the standard clean cycles.
NOTE:
In Figure 6-7 , when EXT SYNC is still active (i.e., it remains
LOW,) at the end of the readout, the hardware may interpret
this as a second sync pulse, and so on.
4
4
11
-00
9
7_0
029
S
HUTTER
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(S
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ORMAL
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S
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