User guide

Page 100 Document No: 11294 LBA-USB User Guide
4.11.3 Percent of Energy Method
LBA-USB measures the lengths of two orthogonal lines that pass through the
beam centroid. The beam widths are determined by separately looking out along
each line and count all the pixels that are greater than the set clip level. The
reported beam widths are the number of pixels greater than the clip level
multiplied by the pixel pitch.
When the Elliptical results are disabled, the computed beam widths are the
measure of the pixels in the row and column that pass through the centroid. The
beam widths in the results window are labeled X and Y.
When the Elliptical results are enabled, the computed beam widths are the
measure of the pixels along the Major and Minor axes that pass through the
centroid. The beam widths in the results window are labeled Major and Minor.
4.11.4 Percent of Peak Method
LBA-USB measures the lengths of two orthogonal lines that pass through the
beam centroid. The beam widths are determined by separately looking out along
each line and counting all the pixels that are greater than the set clip level. The
reported beam widths are the number of pixels greater than the clip level
multiplied by the pixel pitch.
When Elliptical results are disabled, the computed beam widths are the
measure of the pixels in the row and column that pass through the centroid. The
beam widths in the results window are labeled X and Y.
When Elliptical results are enabled, the computed beam widths are the
measure of the pixels along the Major and Minor axes that pass through the
centroid. The beam widths in the results window are labeled Major and Minor.
4.12 Elliptical Beam
LBA-USB computes and displays the Orientation of an Elliptical or rectangular beam
and a coefficient of Roundness. The criteria for computing the Elliptical beam's Major
and Minor beam widths are described in the Beam Widths and Diameters section.
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, open the Aperture dialog box from the
Options menu, go to Display Beam Width and select Ellipse.