SVS-Vistek eco4050, Руководство пользователя

Страница: 48 / 138

SVS-VISTEK
Feature-Set 48
7.1.12 Offset
For physical reasons the output of a sensor will never be zero, even the
camera is placed in total darkness or simply closed. Always there will be
noise or randomly appearing electrons that will be detected as a signal
(dark noise: noise generated without light exposure).
To avoid this dark noise to be interpreted as a valuable signal, an offset
will be set.
Figure 27: Illustration of dark noise cut off by the offset
Most noise is proportional to temperature. To spare you regulating the
offset every time the temperature changes. A precedent offset is set by the
camera itself. It references certain pixels that never were exposed to light
as black (refer to “
resolution – active and effective ”). So the offset will be
set dynamically and conditioned to external influences.
The offset can be limited by a maximum bit value. If higher values are
needed, try to set a look up table.
In case of multi-tap CCD sensors, offset can be altered for each tap
separately (see tap balancing).