Figure 21. Binning And Array Orientation - Princeton PIXIS-XB System User Manual

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This restriction strongly limits the number of pixels that may be binned in cases where there
is a small signal superimposed on a large background, such as signals with a large
fluorescence. Ideally, one would like to bin many pixels to increase the S/N ratio of the weak
peaks but this cannot be done because the fluorescence would quickly saturate the CCD.
The solution is to perform the binning in software. Limited hardware binning may be used
when reading out the CCD. Additional binning is accomplished in software, producing a
result that represents many more photons than was possible using hardware binning.
Software averaging can improve the S/N ratio by as much as the square-root of the
number of scans. Unfortunately, with a high number of scans (i.e., above 100) camera 1/f
noise may reduce the actual S/N ratio to slightly below this theoretical value. Also, if the
light source used is photon-flicker limited rather than photon shot-noise limited, this
theoretical signal improvement cannot be fully realized. Again, background subtraction
from the raw data is necessary.
This technique is also useful in high light level experiments, where the camera is again
photon shot-noise limited. Summing multiple pixels in software corresponds to collecting
more photons, and results in a better S/N ratio in the measurement.
Array Orientation
For square format CCDs (for example, 512 × 512B or 1024 × 1024F/B) you may orient
the CCD to achieve binning along either direction of the CCD.

Binning along columns provides maximum scan rate.

Binning along the rows minimizes crosstalk and is therefore better for multi-spectral
applications.
Note: You can easily switch between these orientations by rotating the camera 90° and
changing the binning parameters in the application software.
PIXIS-XB System Manual

Figure 21. Binning and Array Orientation

Version 2