Redstone™ Optical Spectrum Analyzer Chapter 8: Operation
Page 61 STN053070-D02
Figure 64. Baseline Correction Window
To perform a baseline correction, click the “Baseline” button in the Reference menu. The Baseline correction
dialog box, which allows you to adjust the baseline correction while viewing the results of your adjustments in
real time, will appear.
Baseline correction can only be performed on one trace at a time. Select the trace you wish to correct from the
Trace combo box in the upper left corner, then select the correction method from the Method combo box directly
below. There are four available methods:
• Spline: N baseline points linearly spaced are placed along the trace, and the local median value is
determined around each point. The baseline is then calculated as a cubic Hermite spline, fitted to the
locations and local median values of the N baseline points. The baseline points are displayed in the
graph in the dialog box, and can be dragged around freely to adjust the baseline. The number of points
to base the calculation upon can be set by the Settings combo box below the Method combo box.
• Polynomial: The baseline is determined by fitting a polynomial to the entire trace. The Settings combo
box allows the order of the polynomial to be set.
• Polynomial Below: The baseline is determined by fitting a polynomial to a set of baseline points. These
points are chosen iteratively. In the first iteration, the entire trace is fit to the polynomial. Next, the points
in the trace that lie below the fitted polynomial are used to designate a new set of baseline points. These
steps are repeated until either no more points can be excluded, or the number of baseline points is less
than (polynomial order + 1).
• Polynomial Above: The baseline is determined in the same fashion as the Polynomial Below method,
but points lying above the fitted polynomial are selected instead.
The input trace, the calculated baseline, and the final corrected trace will be displayed in the Baseline Correction
dialog box. When you are satisfied, use the Output combo box to select the trace to which you wish to export
the corrected trace, and click “Ok.” The corrected trace will appear in the main window.
8.11. Keyboard shortcuts
• Ctrl+N: Collect a new single spectrum/interferogram
• Ctrl+R: Start/stop repeated measurements
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