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Chapter 5 Operation 69
The readout rate for n × n binning is approximated using a more general version of the
full resolution equation. The modified equation is:
(3)
On-Chip Binning for Interline
Binning is the process of adding the data from adjacent cells together, and it can be
accom
plished in either hardware or software. Rectangular groups of cells of any size may
be binned together, subject to some hardware and software limitations.
Hardware binning is performed before the signal is read out by
the preamplifier. For
signal levels that are readout noise limited this method improves S/N ratio linearly with
the number of cells grouped together. For signals large enough to render the camera
photon shot noise limited, the S/N ratio improvement is roughly proportional to the
square-root of the number of pixels binned.
Figure 26 shows an example of 2 × 2 binning. Each cell of the im
age displayed by the
software represents 4 cells of the CCD array. Rectangular bins of any size are possible.
Empty Readout Register. Exposure has ended
and image has been shifted to storage cells.
Charges from two storage cells in each column has
been shifted to Readout Register. and added.
After sum of first four charges have been transferred
from Output Node, next four charges are shifted into
Output Node and added.
Four charges have been shifted to the Output
Node and added.
A1 B1 C1
A2 B2
A4
A3
B4
B3
A6
A5
B6
B5
C2
C4
C3
C6
C5
D1
D2
D4
D3
D
6
D5
A4
A3
B4
B3
A6
A5
B6
B5
C4
C3
C6
C5
D4
D3
D
6
D5
C1
C2
+
D1
D2
+
A1
A2
+
B1
B2
+
+
A4
A3
B4
B3
A6
A5
B6
B5
C4
C3
C6
C5
D4
D3
D
6
D5
C1
C2
+
D1
D2
+
+
A4
A3
B4
B3
A6
A5
B6
B5
C4
C3
C6
C5
D4
D3
D
6
D5
A1
A2
+
C1
C2
+
D1
D2
+
B1
B2
+
12
43
Figure 26. 2 × 2 Binning for Interline CCD