Princeton Instruments PI-MAX 3 System, Manual, Page: 47 / 150

Chapter 5 General Operation Factors 47
Software Binning
Software binning is a software-averaging post-acquisition process that can be performed on
either unbinned or hardware-binned data. This type of binning can improve the S/N ratio
by as much as the square root of the number of binned pixels. 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 (1/f
noise) limited rather than photon shot-noise limited, this theoretical signal improvement
cannot be fully realized. Again, background subtraction from the raw data is necessary.
Software binning 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.
In the WinX application software, software binning can either be set up to occur
automatically or as a manual post-processing operation. Automatic software binning is
set up by entering
Group parameters on the
Acquisition|Experiment Setup…|ROI
Setup tab card and then selecting the Use Software Binning checkbox. The drawback to
automatic binning is that the raw data is lost. Alternatively, you can acquire raw data and
then use the post-processing binning function (located on the
Process|Binning and
Skipping…
dialog box) to select the input data, enter the binning parameters, and save
the result to an appropriately named file.
Digitization
During readout, an analog signal representing the charge of each pixel (or binned group
of pixels) is digitized. The number of bits per pixel is 16.
Some PI-MAX3 cameras have two complete analog channels including separate A/D
converters. Because the readout noise of CCD arrays increases with the readout rate, it is
sometimes necessary to trade off readout speed for high dynamic range. The two analog
converters, both high speed, are optimized for slower read rates by digitally processing
the signal in the camera before transferring it to the host.
Logic Out Control
The TTL-compatible logic level output (0 to
+3.3 V) from the
LOGIC OUT connector on the
rear panel can be used to monitor camera status
and control external devices. By default, the
logic output level is high while the action is
occurring. The timing of the level changes
depends on the output type selected on the
Setup|Hardware|Controller/Camera tab page:

Acquiring: After a start acquisition
command, this output changes state on
completion of the array cleaning cycles
that precede the first exposure. Initially
low, it goes high to mark the beginning of
the first exposure. In Focus mode
operation it remains high until the system
Figure 16. PI-MAX3 Setup|
Hardware|Controller/Camera tab page