Specifications

Appendix G Interline CCD Cameras 91
A subsection of the CCD can be read out at full resolution, sometimes increasing the
readout rate while retaining the highest resolution in the region of interest (ROI).
Image readout with binning
Binning is the process of adding the data from adjacent cells together. It can be
accomplished 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 47 shows an example of 2 × 2 binning. Each cell of the image displayed by the
software represents 4 cells of the CCD array. Rectangular bins of any size are possible
.
A1
A2
A3
A4
A5
A6B6
B5
B4
B3
B2
B1C1D1
C2D2
C3D3
C4D4
C5D5
C6D6
1. Imaging cells empty.
Charges shifted to
storage cells.
+
A5
A6
B5
B6
C5
C6
D5
D6
+
+
+
A1
A2
A3
A4B4
B3
B2
B1C1D1
C2D2
C3D3
C4D4
2. Charges from two storage
cells in each column shifted
to readout register and added.
C5
C6
D5
D6
+
A1
A2
A3
A4B4
B3
B2
B1C1D1
C2D2
C3D3
C4D4
++
+
A5
A6
B5
B6
+
3. Four charges shifted to
output node and added.
4. After sum of first four chages
has been transferred out of
output node, next four charges
are shifted into output node
and added.
A1
A2
A3
A4B4
B3
B2
B1C1D1
C2D2
C3D3
C4D4
A5
A6
B5
B6
+
++
Figure 47. 2 × 2 binning for images