Biomedical Engineering Reference
In-Depth Information
Fig. B2. Measurements to determine
x
and
y
scan linearity.
Fig. B3. Method to measure
z
range.
B2.2
z calibration
A sample that has a known
z
height step is scanned. A large number of such standards
are available, see Appendix A. The step height is measured from the images and
compared to the known dimension. There are a number of ways to measure step height.
Histogram-based measurements can be used, but the image must be carefully levelled.
Perhaps the most reliable method is the ISO 5436 method, using a line profile that's an
average of several lines. See Chapter 5 for details on accurately measuring heights from
AFM images.
B2.3 Z linearity
In order to determine the linearity of measurements in the
z
axis, the image acquired in
Section B.2.1 is used. The heights of the features spread across the image, and hence
across the
z
range are measured, and compared, as shown in Figure B4.
Fig. B4. Method to measure
z
linearity.
