Part 2 of the EN focal spot measurement standard uses the same pinhole evaluation method as . As the ASTM standard is described in detail the EN edition will be handled shortly and only differences are highlighted.
As E1165 was updated in 2011 to fit digital evaluation (and with the new ILP method) also EN12543-2 was updated for the 2008 edition. The 2008 edition differs from the 1999 edition in subclauses 4.3, 4.4, 5.1 and 5.2 for inclusion of digital detectors beside the film method.
ASTM E1165 may be used for focal spot with 50µm and larger. EN12543-2 is intended for focal spot sizes with 200µm and larger. In the conclusion the test equipment differs with the smallest size of the pinhole (E1165 requires one smaller pinhole):
E1165: 10µm pinhole diameter for focal spot sizes from 50µm up to 300µm; 30µm from 300µm up to 800µm; 100µm for larger
EN12543-2: 30µm pinhole diameter for focal spot sizes from 200µm up to 1000µm; 100µm for larger
I am not quite happy with the "large" diameter for small focal spots. The unsharpness due to the pinhole is
Ug = P(1+n/m) definitions of P, m and n in tables of
Let me take the same example as in the E1165 thread:
A 250µm focal spot size using the 30µm pinhole: The unsharpness is 120µm and based on spatial resolution 60µm (Ug/2) which is 24%
. Here is a table showing the physical data coming with the requirements of EN12543-2 - when using a digital detector with 20µm pixel size (best in class):As the update of EN12543-2 was before the "invention and verification" of the Integrated Line Profile method (ILP) the evaluation is still the 10% isodose contour line as explained in .