Andor Technology Neo sCMOS, Руководство по оборудованию

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FEATURES & FUNCTIONALITY
Neo
SECTION 2
Page 31
2.3.3 - Choosing Rolling or Global Shutter
Whether Rolling Shutter or Global Shutter is right for you will depend very much on the experiment. 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. That is
to say, if you experience distortion of an object in rolling shutter, you were likely to see smearing of the object in
a CCD camera operated with the same exposure time and frame rate. This same principle holds true for global
shutter mode or any other method of controlling exposure time.
Consider a relatively aggressive example. Consider a migrating vesicle within a cell, the image of the vesicle
being 30 pixels diameter on the sensor. Let’s say we set up a kinetic series rate of 100 fps, sampling the
moving vesicle with an exposure every 20 pixels of movement (even this is an extreme example as the 30 pixel
diameter vesicle would be distorted by 20 pixels to become elongated in shape). The time taken for the readout
front to traverse the 30 pixels distance from bottom to top of the vesicle is 300 μ s. During this time, the fast
moving vesicle would only have moved a distance equating to 0.6 pixel (i.e. sub-pixel). Thus, even under this
relatively aggressive condition, sub-pixel spatial distortion is all that can be expected – when compared to the
distortion caused by movement of objects within an exposure time, this can be considered negligible.
For some particular applications however, global shutter will be viewed as a necessity and these are
exemplified on the next page.
Table 1: Comparing the pros and cons of rolling vs global shutter
Parameter Rolling Shutter mode Global Shutter mode
Frame Rate Maximum available Maximum frame rate is halved
Read Noise Lowest Increased by 1.41
Spatial Distortion Dependant on object dynamics and frame rate None