User guide

LBA-USB User Guide Document No: 11294 Page 103
For the Y or Minor axis:
2
2/
2
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
−
=
m
w
mm
m
eJJ
Where: J = Amplitude at the point m
J
m
* = Amplitude at the Gaussian center
m = Location of pixel
m = M location of the Gaussian center
w
m
* = Width at 1/e² of energy
Parameters marked with an asterisk (*) are the variables fitted.
M
&
m
are not the same as the displayed Centroid Major and Centroid Minor results.
However, they are used to compute those results items.
Note: There are some display limitations when using the Line Gaussian Fit results. If
Reference Source is set to either Last Gauss or Auto Gauss, no full frame
Gaussian beams will be available to be placed into the Reference frame buffer.
Thus, any Beam Display selections that involve the Reference frame will not be
updated nor display any images based on the Line fit results. Use only Whole
Beam fits if you want to use them in conjunction with the various Beam Display
options.
4.16 Deviation of Fit
The Deviation of fit result is a measure of the standard deviation of the beam intensity
data from the fitted Gaussian surface or line. As this result approaches zero the data
more nearly matches the Gaussian surface.
The definition of the Deviation is:
σ =
−
−
∑
()Zs
n
2
2
Where: σ = Standard deviation
Z = Pixel intensity
s = Gaussian surface intensity
n = Number of pixels
For Line fits there will be a separate Deviation result for each axis.