Percent in aperture, Peak and min, Peak location – SIGMA LBA-708 User Manual
Page 131: Centroid location, 7 percent in aperture, 8 peak and min, 9 peak location, 10 centroid location
energy
results. The Units entry will determine the energy units that will appear behind the various
energy
displays, i.e., Peak mw/cm², etc.
If you are using a Drawn Aperture (without an Auto Aperture), then the Total Energy is the amount
of
energy
inside the Drawn Aperture.
If you are using an Auto Aperture (with or without a Drawn Aperture), then the Total Energy is the
amount of
energy
inside the Auto Aperture. Thus...
An Auto Aperture takes precedent over a Drawn Aperture.
6.7 Percent in Aperture
If you place a Drawn Aperture onto the beam display, the percentage of the total
energy
of the
frame that lies inside of the Drawn Aperture will be computed.
If an Auto Aperture is present, then the value will represent the total energy contained within the
Auto Aperture.
If no aperture is present, then this result will show 100%.
Auto Aperture takes precedent over a Drawn Aperture.
6.8 Peak and Min
These are the Peak and Minimum
energy
density values in the displayed frame, or within the Drawn
or Auto Aperture if present. The Minimum value will most often be negative, and is therefore not
meaningful except as an indication of the amount of noise present in the video signal.
Auto Aperture takes precedent over a Drawn Aperture.
6.9 Peak
Location
This is the first location where the peak intensity value was found. The Peak Location is found by
scanning the pixel data from left to right, and top to bottom. If a Drawn or Auto Aperture is
present, then the scanning is confined to the pixels inside the aperture.
Auto Aperture takes precedent over a Drawn Aperture.
6.10 Centroid Location
The Centroid location is found by calculating the center of mass of all the pixels that satisfy the
following clip level criteria, based upon the chosen Beam Width Method.
• In the case of Percent of Peak, the included pixels are those that are greater than the Clip%
level.
• With Percent of Energy, the included pixels are those that are greater than or equal to the
Clip% level.
• If the 4 Sigma or one of the Knife Edge methods are chosen and the Top Hat calculations are
not checked, the clip level is set to 86.5% of energy. If the Top Hat calculations are checked,
then an 80% of Peak clip level is set.
Operator’s Manual
LBA-PC
Doc. No. 10654-001, Rev 4.10
131