Readout Time; Figure 38. Full Frame At Full Resolution - Princeton Instruments ProEM+ EMCCD User Manual

Chapter 5 Operation 75
Referring to Figure 37, it can be seen that exposure and readout are carried out in a
sequential fashion. As a result, each frame in the sequence is precisely exposed for the
time specified (i.e., 10 ms).
Full Frame Readout for Full Frame EMCCD
The upper left drawing in Figure 38
represents a full frame EMCCD
after exposure but before the
beginning of readout. The capital
letters represent different amounts
of charge, including both signal and
dark charge. This section explains
readout at full resolution, where
every pixel is digitized separately.
In this drawing, the charge is being
read out of the Low Noise port.
Note: The Multiplication {Electron
Multiplied} port is not shown in
this drawing.
Readout of the CCD begins with
the simultaneous shifting of all
pixels one row toward the "shift
register," in this case the row on the
top. The shift register is a single
line of pixels along the edge of the
EMCCD, not sensitive to light and

Figure 38. Full Frame at Full Resolution

used for readout only. Typically the
shift register pixels hold twice as much charge as the pixels in the imaging area of the
CCD.
After the first row is moved into the shift register, the charge now in the shift register is
shifted toward the output node, located at one end of the shift register. As each value is
"emptied" into this node it is digitized. Only after all pixels in the first row are digitized is
the second row moved into the shift register. The order of shifting in our example is
therefore A1, B1, C1, D1, A2, B2, C2, D2, A3.... After charge is shifted out of each pixel,
the remaining charge is zero, meaning that the array is immediately ready for the next
exposure.
A subsection of the CCD can be read out at full resolution, sometimes dramatically
increasing the readout rate while retaining the highest resolution in the region of interest
(ROI).

Readout Time

In WinX, readout time can be obtained by going to the Acquisition menu and selecting
Readout Time... In LightField, it is reported on the Sensor expander. Readout time is
calculated based on the current ROI/Binning/Vertical shift rate settings.
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