SIGMA LBA-708 - Manual (Page 90)

to use it as it relates to pixel units on the detector array. If you choose to do pointing stability
using spatial units such as mm or µm; the bins of the scatter/histogram plot and the horizontal
and vertical grid lines will not have any correlation to the individual pixels on the detector.
In other words, the bins in the histogram and the pixel grid of the detector will not have the
same crosshatch granularity. On the other hand, if you do it from the pixel-units standpoint, the
bins on the histogram will correlate with the size of the pixel grid on the detector. The
drawback however, is that you will be forced to multiply the results by the pixel scale of the
detector to get the data into real world units of distance.
The units on the horizontal and vertical axes of the scatter plots will change depending on how
you setup LBA-PC. They could be microns, millimeters, and fractions of pixels or any of the units
that are offered in LBA-PC. In short, the units on the X/Y-axes of the histogram/scatter plots are
the same as the units selected in LBA-PC for quantitative results. You can select these units by
going to LBA-PC’s main menu and selecting:
Options > Camera > Pixel Units
If, for example, you desired to see which pixels on the camera most often contained the peak of
your beam, setup your histogram bins to work in terms of individual camera pixels. To do this go
to the main menu on LBA-PC and select:
Options > Camera
From the camera dialog you would select the camera that matched your detector and then select
the Pixel Units to be PX (or pixel units). In the Pixel Scale spin control you would enter 1.0
to tell LBA-PC that your pixels are one pixel wide. Before closing the dialog you should make
sure that the Resolution drop down box is set to 1X. Resolutions other that 1X may be used
but this will be discussed later. In this example we will choose 1X because we do not want to
limit which pixels the peak might fall upon. Click OK to accept the changes to the camera dialog.
Now we will setup the origin in LBA-PC to match that of the histogram plot. On the main menu
select:
Options > Beam Display
Set the Origin Location to Window LL to coincide with the Beam Stability plot convention.
Setting the origin to values other that Window LL will work but the user should be aware that the
beam window and histogram might be horizontally or vertically inverted with respect to one
another.
Make sure that LBA-PC is collecting data and return to the Beam Stability window. Press the
reset button to restart the histogram.
Note: Whenever units are changed in LBA-PC, the scatter plot should be reset because previously plotted samples
will not be adjusted to reflect the new plot axis dimensions.
Operator’s Manual LBA-PC 90