Filter
Top Products
Chapter 5 Operation 61
to the output amplifier where the electrons are grouped as electrons/count. This result
leaves the CCD and goes to the preamplifier where gain is applied.
WinView and WinSpec allow you to specify the type of readout, binning, the output
am
plifier, and the gain (the number of electrons required to generate an ADU).
Note: The type of readout (full frame, frame transfer, or interline) depends on the CCD
array installed in the camera.
The upper left drawing in Figure 21 represents a CCD after exposure but before the
beginning of readout. The capital letters repr
esent different amounts of charge, including
both signal and dark charge. This section explains readout at full resolution, where every
pixel is digitized separately.
Empty Readout Register Readout Register with charge
from first line.
Charge from first cell shifted
into Output Node.
After first line is read out,next line
can be shifted into empty
Readout Register.
A2
A1
B2
B1
C2
C1
D2
D1
A4
A3
B4
B3
C4
C3
D4
D3
A6
A5
B6
B5
C6
C5
D6
D5
A1 B1 C1 D1
A2 B2 C2 D2
A4
A3
B4
B3
C4
C3
D4
D3
A6 B6
C6
D6
A2 B2 C2 D2
A4
A3
B4
B3
C4
C3
D4
D3
A6 B6
C6
D6
A2
A1
B2
B1
C2
C1
D2
D1
A4
A3
B4
B3
C4
C3
D4
D3
A6 B6
C6
D6
A5 B5 C5 D5
A5 B5 C5 D5 A5 B5 C5 D5
43
12
Figure 21. Full Frame at Full Resolution
Readout of the CCD begins with the simultaneous shifting of all pixels one row toward
the "shift register", in this case the row at top. The shift register is a single line of pixels
along one edge of the CCD, not sensitive to light and used for readout only. Typically the
shift register pixels hold twice as much charge as the pixels in the imaging area of the
CCD.
After the first row is moved into the shift register, the charge now in the shift register is
shifted toward the output node, located at one end of the shift register. As each value is
"em
ptied" into this node it is digitized. Only after all pixels in the first row are digitized is
the second row moved into the shift register. The order of shifting in our example is
therefore A1, B1, C1, D1, A2, B2, C2, D2, A3....