User guide

Page 94 Document No: 11294 LBA-USB User Guide
process primarily fix the noise level, most of our efforts concentrate on increasing the
signal content.
Always try to optimize the beam's amplitude into the camera's dynamic operating range.
Whenever possible, use external optical attenuation to bring the beam's peak signal
levels into the upper half of the video signal's dynamic range. If optical attenuation
results in low signal amplitude, use the camera's video gain control to restore some of
the loss.
Note: Increasing gain also increases noise, so use it sparingly.
Always use the smallest region of interest (ROI) that adequately contains all of the
beam's energy.
If beam intensity is low and/or covers only a small fraction of the display window, use
an aperture to eliminate the background energy noise in the wings.
Use external optical magnification if the beam begins to approach only a few pixels in
width. Widths of at least 10 pixels are required to obtain a reliable beam width
measurement.
4.4 Manual Background Energy Nulling
Manual Background Energy Nulling is NOT recommended. Use the Ultracal! calibration
feature instead.
Do not place any confidence in the computed results until background energy results
have been nulled using Ultracal!.
LBA-USB provides three different methods to assist in the removal of unwanted
background energy from the quantitative calculations:
 Ultracal! calibration.
 A Drawn Aperture around the energy of interest, isolating the beam and effectively
forcing all the energy outside the aperture to zero.
 An Auto Aperture feature that draws an optimally sized aperture around the beam
energy.
4.4.1 What is Ultracal!?
The Ultracal! processing feature should be used in the place of any manual
energy nulling techniques. Ultracal! employs a sophisticated proprietary
algorithm that yields greatly improved accuracy over various operating conditions
and signal dynamic range. In addition, it can quickly be rerun if changes in setup
or conditions occur as required by modifications to experimental conditions.
Before performing an Ultracal! be sure to optimize the beam’s presentation. This
is essential as the Ultracal! cycle results will be specific to the current ROI and
Video Gain settings. Consider placing a manually drawn aperture at this time, or
later if desired. The aperture is not locked by the calibration cycle and may be
manipulated by the operator at any time.
The Ultracal! cycle can be run at any time, whether in 2D or 3D mode. The beam
must be blocked from the camera detector. After completion of the Ultracal!
cycle, the subsequent results remain accurate as long as the setup conditions