From the designation Charge Coupled Device (CCD), the principle of CCD sensors emerges, namely the charge transfer of the charge image.
In this process, the charge image, which is an image of the light intensity of each individual pixel, is shifted step by step and transported to the end of the line where it is read out. This shifting process is subject to small losses, which are expressed in the Charge Transfer Efficiency (CTE).
The CTE value represents the ratio of the shifted charge present at the output to the charge previously stored in the respective pixel. The CTE value is sensor-specific, dimensionless and can be a maximum of 1 according to the definition described above, namely when no charge displacement losses occur. Otherwise it is always less than 1.