LBP2 User Guide
Document No: 50306-001
Rev G 3/12/2020
Page 71
CHAPTER 5
Computations
5.1
Computational Accuracy
The degree of accuracy of the computed results is based primarily on two factors. The
first, and most significant, is the correct nulling of the camera background signal. The
second deals with optimizing the presentation of the beam display within the detector
and/or within a properly sized aperture.
The background nulling operation establishes the zero reference from which all
computed results are based. Failure to correctly null and periodically monitor the
background energy will yield inconsistent results. Excessive background energy levels
will yield oversized beam diameters and reduced magnitudes when energy
relationships are compared. The opposite effects will result if the background levels
are excessively suppressed.
LBP2 is equipped with a patented auto calibration feature called Ultracal. Ultracal
performs a nulling operation that is significantly more accurate than that which can be
achieved manually. The Ultracal algorithm also compensates for background noise,
imager point defects, and camera shading.
5.1.1
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, it is recommended that the beam’s presentation be
optimized. Any changes to camera settings (Gain, Exposure, ROI, etc.) will
invalidate the current Ultracal. Auto and Manual apertures are not locked by the
calibration cycle and may be manipulated by the user at any time.
Ultracal will fail if there is excessive noise in the signal. This can be improved by
decreasing the gain. If Ultracal continues to fail, there may be a “dark” pixel. If
this is the case, a bad pixel correction will be needed and the camera must be
returned for repair.
The Ultracal cycle can be run at any time. 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 remain the same, and the camera
black level, shading and noise conditions do not change.
Since some cameras can drift with temperature, it’s recommend performing an
Ultracal cycle every 10 to 15 minutes, or whenever the camera may have strayed.
This drift can be observed as changes to the background noise image. Un-
illuminated areas appear as gray and dark violet (almost black) random noise. If
