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2.3.1 Spurious Noise Filter
The
Spurious Noise
filter corrects for pixels that would otherwise appear as spurious ‘salt and pepper’ noise
spikes in the image. The appearance of such noisy pixels is analogous to the situation of Clock Induced Charge
(CIC) noise spikes in EMCCD cameras, in that the overall noise of the sensor has been reduced to such a low
level, that the remaining small percentage of spurious, high noise pixels can become an aesthetic issue. The
filter actively corrects such high noise pixels, replacing them with the mean value of the neighbouring pixels
The filter can be switched on and off by the user prior to data acquisition.
Figure 11:
Demonstration of Spurious Noise Filter (Filter On left, Filter Off, Right) on a dark image, 20 ms exposure time, 200 MHz (x2
halves) readout speed
2.3.2 Blemish Correction
This
Blemish Correction
filter identifies and compensates for three types of blemishes during the FPGA
processing step:
1. Hot Pixel’s
2. Noisy Pixel’s
3. Unresponsive Pixel’s
sCMOS sensors are particularly susceptible to hot pixel blemishes. These are spurious noise pixels that have
significantly higher darkcurrent than the average. Through deep TE cooling of the sensor (e.g. -30
o
C in the
Neo), it is possible to dramatically minimize the occurrence of such hot pixels within the sensor, meaning that
these pixels can still be used for useful quantitative imaging. However, if deep cooling cannot be achieved it is
necessary to use interpolative filters to minimize the hot pixel blemishes. These filters work by taking the mean
of the surrounding 8 pixel values and replacing this hot pixel blemish with this mean value. Such interpolation
over pixel blemishes can be detrimental in some applications that depend on total quantitative integrity over a
limited set of pixels, for example in localization based super-resolution microscopy (such as PALM and STORM
techniques) and astronomy. In these applications it is essential for the user to be able to switch off interpolative
corrections.
Furthermore, having access to the location of these blemishes allows an accurate map of ‘good’ pixels to be
determined by the user. A new service allows the end user to request a ‘hot pixel map’ of their sCMOS sensor
from Andor. This map will be generated based on the experimental conditions outlined by the end user.
From the latest general release of Andor SDK3 (version 3.7.30004) and Solis (version 4.24.30004) blemish
correction can be switched on and off by the user. Refer to the SDK and Solis User Guide and help information
for instructions.
Summary of Contents for Zyla sCMOS 4.2 PLUS
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