Chapter 5 Gate Mode Operation 65
• Skip Serial Register Clean (deselected) {Clean Serial Register} The Top margin
inactive parallel strips on a CCD are made up of the dark pixels that come before
the active strips on a sensor as they exit to the serial register. When these are
available (i.e., Pre Dummies {Top Margin} > 0,) they serve the purpose of cleaning
the serial register before readout of the active strips. In LightField, if there are no
inactive parallel strips (i.e., {Top Margin} = 0,) selecting
Clean Serial Register
forces a clean of the serial register before readout of the active strips.
The start of the exposure is signaled by the Read Out
{
Reading Out} output of the LOGIC OUT connector going
low but will not occur until the current clean cycle and the
additional user-defined number of cleans (typically 0) have
finished. “Number of Cleans” is defined on the
Setup —>
Hardware —> Cleans/Skips
tab {Sensor Cleaning fly-out
pane on
Sensor expander}. If you enter a value other than “0”,
you will further delay the start of the exposure by that number
of clean cycles.
5.4 Phosphor Decay Delay
The WinX and LightField applications allow a delay between the end of the exposure time
and the beginning of the array readout to be specified. This time is inserted to allow the
phosphor to decay to 1% before readout occurs and will vary depending on the phosphor
type. This delay has no effect on the actual time it takes for the phosphor to decay.
In the case of an experiment using a PI-MAX4:1024i and a
very short exposure time, artifacts will appear in the first frame
unless the phosphor decay delay is set to 3 ms. This amount of
delay will ensure that the vertical registers (under the mask) are
cleared before the acquired signal is shifted under the mask.
Figure 5-3 and Figure 5-4 show the dialogs on which the custom decay delay time is
configured.
