version 1.5 rev 4 Dec 2019
29
Sona &
Marana
4.4.3 U
sing
Roi
s
(aoi
s
)
Region of Interest (ROI) also called Area of Interest (AOI) can be selected so that only a defined region of the sensor is
used. This smaller “cropped” region of the sensor can subsequently be read out much faster than the full sensor area so
that frame rates may be significantly higher (see the preceding table). Preset ROIs may be selected as well as manually
defined ROIs with a 1 pixel granularity [min size. 1(h) x 25 (w)].
Figure 5: ROIs can be used to focus on a sub-region of an image.
4.4.4 b
inning
Binning is a process used for both CCD and sCMOS sensors in which the signal for a number of pixels is combined into
a single array with a single signal output. For CCD sensors combining the charge from arrays of pixels e.g. 4 pixels (2x2
binning) into single larger “super-pixels” allows the read noise (the dominant noise source in CCDs) to be reduced since
there are less read events. Binning is therefore commonly used for CCD cameras to increase the signal to noise ratio and
speed of readout, at the expense of lower resolution. For further information refer to the technical note:
However, for cameras with sCMOS sensors such as in the Andor Zyla, Neo, Sona and Marana models, the binning
process is performed slightly differently. Binning is processed by the FPGA after the pixels have been readout- therefore
there is not the speed increase observed in CCD cameras from the reduced number of pixels being read out. After FPGA
processing the pixel information is transmitted to the control PC - this may be faster when binning is applied under some
conditions. For further information refer to the technical note:
.
4.4.5 s
pURioUs
n
oise
f
ilteR
The overall noise of the sensor is at such a low level, that under some conditions, the remaining small percentage of
spurious, high-noise pixels can become an aesthetic issue. The
Spurious Noise Filter
actively corrects such high noise
pixels, replacing them with the mean value of the neighbouring pixels. The filter can be switched off by the user prior to
data acquisition experiments.
