version 2.0 rev 18 Feb 2021
19
2.2.2 Global Shutter (Zyla 5.5 only)
Global shutter mode, which can also be thought of as a ‘snapshot’ exposure mode, means that all pixels of
the array are exposed simultaneously. In most respects, global shutter can be thought of as behaving like an
Interline CCD sensor. Before the exposure begins, all pixels in the array will be held in a ‘keep clean state’, during
which charge is drained into the anti-bloom structure of each pixel. At the start of the exposure each pixel
simultaneously begins to collect charge and is allowed to do so for the duration of the exposure time. At the
end of exposure each pixel transfers charge simultaneously to its readout node. Importantly, global shutter can
be configured to operate in a continuous ‘overlap’ mode (analogous to Interline CCD), whereby an exposure can
proceed while the previous exposure is being readout out from the readout nodes of each pixel. In this mode,
the sensor has a 100% duty cycle, again resulting in optimal time resolution and photon collection efficiency.
However, the mechanism of global shutter mode demands that a reference readout is performed ‘behind the
scenes’, in addition to the actual readout of charge from each pixel. Due to this additional reference readout,
global shutter mode carries the trade-off of halving the maximum frame rate that would otherwise have been
achieved in rolling shutter mode. In addition, global shutter also increases the RMS read noise by a factor of
1.41 over rolling shutter readout.
Figure 9
below shows a simplified illustration showing sequence of events in
global shutter mode:
Figure 9: Global Shutter Exposure and Readout
Summary of Contents for Zyla sCMOS 4.2 PLUS
Page 76: ...version 2 0 rev 18 Feb 2021 76...
