AvaRaman Operating manual AvaSoft Raman 7.3 November 2008

The spline interpolation can be
useful for applications in which
the output of line sources, like
laser diodes is displayed, or for
other applications, which
require a high resolution. Note
that for the AvaSpec-2048 with
2048 pixels, the effect of
spline interpolation is not
visible if the data is shown at
full scale. The monitor
resolution is much less than
2048 pixels. The effect of
spline interpolation can only
be visualized if the number of
detector pixels that are
displayed is smaller than the
number of monitor pixels at
the x-axis.
Smoothing
To get a smoother spectrum without losing information it is important to set in the software the
right smoothing parameter. The optimal smoothing parameter in a standard AvaRaman system with
50 micron slit is 1, in which case the data at each pixel will be averaged with one neighbor pixel at
the left and one at the right. This can be done without losing resolution, because the 50 micron
beam will cover at least 3 detector pixels (the distance between the pixels at the CCD detector is
14 micron). The AvaRaman-TEC includes a 25 micron slit in which case the smoothing should be set
to zero.
If resolution is not an important issue, a higher smoothing parameter can be set to decrease noise
against the price of less resolution.
2.3.2.4 Setup Menu: Correct for Dynamic Dark
The pixels of the CCD detector (AvaSpec-2048) are thermally sensitive, which causes a small dark
current, even without light exposure. To get an approximation of this dark current, the signal of the
first 14 optical black pixels of the CCD-detector can be taken and subtracted from the raw scope
data. This will happen if the correct for dynamic dark option is enabled. As these 14 pixels have the
same thermal behaviour as the active pixels, the correction is dynamic.
If this menu option is preceded by a checkmark, the scope data is corrected with the dynamic dark
algorithm. It is recommended to leave this setting checked, which is the default state.
32 AvaRAMAN manual.doc Nov-08
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