LBP2 User Guide
Document No: 50306-001
Rev G 3/12/2020
Page 86
APPENDIX A
ISO Computations Table
This table of ISO computations follows the labeling and notions found in the ISO
standards. Where differences exist within the standards, no particular preference is
given to any one notation. The information contained here may not always agree
with the latest releases of the individual standards; however, it will be updated from
time to time as the ISO standards evolve. The Section numbers in the list may also
break when ISO standards are reformatted. The ordering of the items follow no
particular sequence and no importance should be attached to the item #.
Note: The symbols and names listed here may or may not agree with the notations
used in LBP2. These notations may be slightly modified for the purpose of
maintaining consistency in labeling within LBP2 and standard industry and legacy
usage. Not all listed results are currently provided in LBP2.
( ) shall contain one of the following symbols
1
u = a measurement based upon a percentage of power/energy, usually an encircled amount or
contained by a smallest slit. The value u shall be replaced with an amount, such as 90,
to mean 90%.
σ = a measurement based on second moment definitions
k = a measurement based on a Knife Edge measurement, usually a 10/90 percent of energy
2
1
The ISO procedures typically refer to two types of beam diameter/width measurements; second moment, and
encircled energy. When dealing with elliptical beams the encircled energy method is modified to a minimum
slit technique, where for a circular Gaussian distribution, 95.4% of the energy contained in a slit is equal to the
second moment width. Also in dealing with elliptical beams the direction of variable slit orientation is
described as being in the “preferential directions”… see 11145 sec 3.5.1. While the “preferential directions”
are rather loosely defined, one can surmise that the later described azimuth directions can be used in its place…
see 11146-1 sec 7.2.
2
The Knife Edge measurement technique is mentioned in 13694 sec 3.2.4 d. It is not given much attention in
the ISO documentation. However it is a valuable measurement technique when correctly applied.
It
em
#
S
ymb
ol
Name
IS
O 1114
5
IS
O
11146
IS
O 1167
0
IS
O 1369
4
IS
O 1536
7
S
ec
tio
n
Definition
1
A
()
A
σ
(z)
beam cross-
sectional area
x
x
3.2.1
3.2.2
3.2.6
Area bounded by the beam
width definition ( )
for circular beams
4
2
d
A
for elliptical beams
4
y
x
d
d
A
2
d
()
beam diameter x
3.3.1
3.3.2
Smallest aperture or second
moment diameter of a
