SEM Quick Star
Revision No.2
May 2014
Page 10 of 16
1.3.4
Scan Speed and Noise Reduction
The data coming from the currently selected detector channel on
the instrument can be sampled and processed differently depending on the
task at hand. The scan speed changes how fast the instrument samples data
from the detector, with higher scan speeds equating to faster sampling
rates (similar to a frame-rate). While exploring the sample, it is often
easier to use a higher scan speed since the viewing window will update
changes in the image more quickly than slower scan speeds. The catch to
this is that at higher scan speeds, more image detail is lost. To investigate
details more effectively, or to capture and save images of the sample,
slower scan speeds are favored. The detector scan speed can most easily
be changed by pressing the
+
or
–
buttons labelled
Scan Speed
on the
right side of the
Zeiss SEM
keyboard. Alternatively, the scan speed
parameters can be viewed and altered using the
Scanning
tab of the
SEM
Control
group located on the software’s side-panel.
Noise is an inherent consequence of any sensing methodology. The
methods by which detector noise is handled by the software are ultimately
averaging processes. For the purposes of this guide only two noise
reduction procedures will be utilized: pixel averaging and line averaging.
Pixel averaging is effective when the operator is actively exploring the
sample, or when the sample image is changing often (e.g. during
magnification of focusing). Line averaging is used when the operator is
inspecting the details of an image, or when the operator wishes to capture
and save an image. Changing the noise averaging mode can be done under
the
Scanning
tab of the
SEM Control
group located on the software’s
side-panel. The second dropdown menu in the
Noise Reduction
box
allows the user to select the appropriate averaging technique.
1.3.5
Reduced Raster
Many of the procedures detailed below can be performed on a
small section of the viewing screen. This is advantageous when the
operator wishes to use a slower scan speed (higher resolution) without
having to wait for the entire frame to be scanned after making changes. To
enable the reduced raster window, click the
Reduced
button directly
above the
Magnification
knob on the left-hand side of the
Zeiss SEM
