The Dual Scan mode is used to save time for the measurement of features with a big z-height difference or in cases where two parts of the sample need to be measured with different sensor settings. It is implemented in combination with the FRT field of view sensors WLI, CFM and CFM DT.
In the Dual Scan mode two single scans are performed, one using the scan parameters of Single Scan 1, the other using the scan parameters of Single Scan 2. Subsequently, the raw data of the two scans is merged to one topography image. For this, the raw data from the Single Scan which is defined as ’Master’ is preferred. Values from the other Single Scan only remain in the resulting image at positions where the topography of the ‘Master’ Single Scan is invalid.
In the Sensor Settings dialog, the measurement is defined by setting the scan limits, lamp intensity, objective and step size for the two single scans separately. For a Dual Scan, the selected objective has to be the same for both single measurements. When the two scans are finished, the composite topography measurement is shown. In order to adjust the composite result the user can use the Post-Processing Dialog. The topography and intensity limits can be set separately for each single scan.
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