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light is blocked. Because without the sample, the light intensity reaching the
detector is higher than with sample, so it might be necessary to select in
OPUS a smaller aperture setting. Change the file name in such a way that the
file can easily be recognized as the file containing the calibration
measurement results. All the other parameter settings should be identical to
the ones of the sample measurement. Turn the controlling unit on again. Then,
start a dual channel measurement (i.e. with both ADC channels of the
detector) as already described in section 4.2 Sample Measurement. Because
the light intensity has been modulated during the calibration measurement, the
inclined lines can now easily be seen in the 3D plot. (See figure 14.) The strain
traces of the calibration measurement will look identical to the ones of the
sample measurement.
Fig. 14: OPUS 3D+ window displaying the single interferograms of the calibration measurement. (The interferograms are in the
“S_IFG” data block of the 3D file resulting from the calibration measurement. These interferograms contain strong modulations
due to the oscillating shutter aperture.
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Bruker Optik GmbH