Clara
29
Version 2.0 rev 24 Mar 2015
Readout Sequence of a CCD
In the course of readout, charge is moved vertically into the shift register, and then horizontally from the shift register into
the output node of the amplifier. The readout sequence illustrated below (which corresponds to the default setting of the
Full
Resolution Image
binning pattern) allows data to be recorded for each individual element on the CCD-chip. Other
binning patterns are achieved by summing charge in the shift register and/or the output node prior to readout (please
refer to
Vertical Binning
and
Horizontal Binning
).
Figure 11: A representation of the readout sequence of a CCD
1
Exposure to light causes a pattern of charge (an electronic image) to build up on the frame (or ‘image area’) of
the CCD-chip.
2
Charge in the frame is shifted vertically by one row, so that the bottom row of charge moves into the shift
register.
3
Charge in the shift register is moved horizontally by one pixel, so that charge on the endmost pixel of the shift
register is moved into the output node of the amplifier.
4
The charge in the output node of the amplifier is passed to the analog-to-digital converter and is read out.
5
Steps 3 & 4 are repeated until the shift register is emptied of charge.
6
The frame is shifted vertically again, so that the next row of charge moves down into the shift register. The
process is repeated from Step 3 until the whole frame is read out.
GLOSSARY
