version 2.0 rev 18 Feb 2021
20
2.2.3 Selecting Rolling or Global Shutter
The selection of Rolling Shutter or Global Shutter modes for the Zyla 5.5 depends on your specific experimental
conditions. A summary of the key parameters for each mode is shown in
.
Table 3: A Comparison of Rolling and Global Shutter Modes
Parameter
Rolling Shutter Mode
Global Shutter Mode (Zyla 5.5 only)
Frame Rate
Maximum available
Maximum frame rate is halved
Read Noise
Lowest
Increased by 1.41
Spatial Distortion
Dependent on object dynamics and frame rate
None
Rolling Shutter Mode
: with the enhanced frame rates and lower noise, is likely to suit the majority of scientific
applications. As long as the frame rate is such that the camera is temporally oversampling object dynamics
within the image area, negligible spatial distortion will be observed. Such oversampling is good imaging
practice, since it is undesirable to have an object travel a significant distance during a single exposure.
Global Shutter Mode
: for some specific applications global shutter will be viewed as a necessity. These are
shown in
Section 2.2.3.1
.
Refer also to Andor Technical Note, “
2.2.3.1 Examples of Typical Applications for Global Shutter Mode
•
Applications that require ‘microsecond’ time gating synced to a pulsed light source
: e.g. Laser
Induced Breakdown Spectroscopy (LIBS). Global readout involves a step that simultaneously transfers
the signal charge of each pixel into the corresponding readout node for that pixel. This transfer step is
2 μs (at 560 MHz readout rate), facilitating fast exposure end, i.e. ‘Electronic gating’
• ‘
Double Exposure’ applications
: e.g. Particle Imaging Velocimetry (PIV), which requires that two back-
to-back exposures are acquired with minimal time separation between them. The global shutter 2 μs
transfer time into the readout node defines the minimum time between two consecutive exposures
•
Applications that require exact time correlation between two (or more) points of an image that
are separated vertically within the image:
In rolling shutter it takes 10 μs per row for the 2x readout
fronts to move across the image from the centre outwards, reading out one row at a time. At 560 MHz
pixel readout rate, this represents 10 ms to cover the distance from centre to outermost rows. That
means an object at the centre of the image will begin and end an exposure ~10 ms before an object
located at the very top or bottom (although remember that each object will be subject to the same
overall exposure time). If a particular application requires that ‘moving or changing’ objects separated
by relatively large distances (vertically) be subject to the same beginning and end of exposure, then
global shutter mode is required
•
Applications where the entire field of view is fast moving (relative to exposure time)
: e.g. high speed
machine vision inspection, such as PCB inspection
Содержание Zyla sCMOS 4.2 PLUS
Страница 76: ...version 2 0 rev 18 Feb 2021 76...
