3.5 Operation for Image Observation
3 - 42
3.5.3 Selecting Scanning Speed
Twelve scanning speeds are available with four buttons.
To select a scanning speed, click one of the Scan speed icons on the Control panel.
Fig. 3.5-13 Scanning Control Unit
Two scanning speeds are assigned to each button. They are set alternately by clicking the
button. The assignment of scanning speeds to four buttons can be customized.
Refer to <2.3.6.3 Scan Control Windows>.
The Run/Freeze (
) button on the Control panel changes run (scans the
electron beam over the specimen, and continuously acquire image) and freeze (blank
electron beam and stop image acquisition) status alternately. While the electron beam is
scanning, the characters "RUN" blink at the upper-left corner of the scanning image. When the
RUN button is clicked, scanning stops after completing the corrent frame.
The characters "Going to Freeze" blink while the scan completes and then changes to "Freeze".
(1) TV Scanning:
TV Scanning of flicker-free images is convenient for a field search of the specimen, coarse
focus, etc. The quality (S/N ratio) of the image is improved by frame averaging.
Two TV scanning speeds, TV1 and TV2, operate at the same speed but allow different
number of frames to be averaged for each.
To set the number of frames to be averaged, use the Image tab in the Setup dialog window.
In the FAST SCAN AVERAGING area, set TV1 and TV2 values. Recommended numbers
are 4 for TV1 and 8 or 16 for TV2. The higher the number of frames, the better the
attainable image quality.
(2) Fast Scanning:
Fast Scanning runs with half the speed of TV scanning. It is also convenient for a field
search of the specimen, coarse focus, etc.
This is the highest possible scanning speed under the full screen mode.
The quality (S/N ratio) of the image is improved by frame averaging.
Two fast scanning speeds, FAST1 and FAST2, operate at the same speed but allow
different number of frames to be averaged for each. To set the number of frames to be
averaged, use the Image tab in the Setup dialog window. In the FAST SCAN
AVERAGING area, set FAST1 and FAST2 values. Recommended numbers are 2 or 4 for
FAST 1 and 4 or 8 for FAST 2.
