Image Acquisition
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Setting a black reference ensures that the image background retains a
uniform darkness, even with exposure times in excess of several seconds. This
setting is therefore particularly recommended for the acquisition of weak
fluorescence or other images with weak light intensity and consequently
long
exposure times (starting from approx. 3 seconds).
Note:
•
Perform this black-value calibration approx. 15 minutes after switching on
the camera, as the camera will then be in a thermally balanced condition.
For this calibration process make sure that the camera is viewing a completely
black image. For example, close the light path to the camera on the
microscope. In exceptional cases it may be necessary to remove the camera
from the microscope for this calibration process and to cover the sensor with
the cap provided.
Calibration takes approx. 20 seconds. At the end of this period it will continue
to be available even if the software is restarted. Under certain circumstances it
may be necessary to repeat this calibration process from time to time.
Notess:
•
The black reference is needed to correct deviations in the dark current for
individual pixels (dark current compensation). This measure is additional
to the camera’s available Peltier cooling, and allows a uniformly dark and
even image background to be achieved, even with long integration times.
•
The ubiquitous phenomenon of environmental radiation can cause
individual bright pixels (hot pixels) on CCD sensors (especially during air
travel). Such pixels are recognized and compensated for by the black
reference. This compensation functions as soon as a measurement has
been carried out, even if the black reference is deactivated.
•
Activating the black reference can reduce the maximum possible speed of
the live image.
56
M 60-3-0014 e / printed 12.2008
