SIGMA LBA-708 - Manual (Page 135)

The Orientation of an Elliptical beam is determined from the clip level. A smaller percent of peak or
larger percent of energy will include more pixels, in the orientation calculation. A larger percent of peak
or smaller percent of energy will include fewer pixels. Depending upon your laser beam this setting can
have serious implications.
The Orientation is defined as the angle formed between the Major axis and the horizontal, pointing
to the right. If the Major axis points above the horizontal, the angle is positive (+); below, the
horizontal is negative (-). The Major and Minor axes are perpendicular to each other.
The Roundness result is the ratio of the computed beam widths. The Minor (smaller) beam width is
always divided by the Major (larger) to produce a result less than or equal to one. Thus, beams with
Roundness values close to 1.000 are nearly circular.
To view the shape of the computed ellipse, select Options, Aperture..., go to Display Beam Width
and select Ellipse.
6.13 Gauss Fit
The LBA-PC can perform a least squares bivariate normal equation (Gaussian equation) fit using all of
the data when doing a Whole beam fit. Or it can perform two univariate normal equation fits using
orthogonal Lines of data through the Centroid Location.
With the Elliptical results disabled, the Gaussian fitter may be set to Disabled, Whole Beam, or X/Y
aligned.
With the Elliptical results enabled, the choices are Disabled, Whole Beam, or Major/Minor aligned.
The Gauss Fit results are displayed as follows:
Whole Beam fits Line fits are X/Y or Major/Minor aligned
Centroid X,Y Centroid X or Major* Centroid Y or Minor*
Width X,Y Width X or Major Width Y or Minor
Height Height X or Major Height Y or Minor
Deviation Deviation X or Major Deviation Y or Minor
Correlation Correlation X or Major Correlation Y or Minor
The Centroid Major value is the distance from the fitted Major axis centroid to the origin axis, which
is most perpendicular to the Major axis. The Centroid Minor value is the distance from the fitted
Minor axis centroid to the origin axis, which is most perpendicular to the Minor axis. At 45° the
Centroid Major value is the distance to the X-axis and the Centroid Minor is the distance to the Y-
axis.
Whole beam fits are always X and Y aligned.
Line fits can be either X/Y aligned where the fits will be performed upon the data in the X & Y
directions passing through the Centroid. Or the fits can be Major/Minor axes aligned with the fits
performed upon the data on the Major and Minor axes passing through the Centroid.
All fits are least square fits, meaning that the algorithm minimizes the sum of the square of the
differences between the data and the fitted surface or line, as described in the following equation.
Operator’s Manual LBA-PC
Doc. No. 10654-001, Rev 4.10
135