ISO/CD 32543-5

Non-destructive testing — Characteristics of focal spots in industrial X-ray systems — Part 5: Focal spot reconstruction technique

Scope

This document specifies a method for the measurement of effective focal spot dimensions below 0,1 mm of X-ray systems by means of the reconstruction technique, applied to digital images taken from hole type or disk type test objects. The image quality and the resolution of X-ray images depends highly on the characteristics of the effective focal spot, in particular the size and the two-dimensional intensity distribution as seen from the detector plane.
This method can also be applied for the measurement of effective focal spot dimensions above or equal to 0,1 mm, but it is preferable to use the pinhole method according to ISO 32543-1:2024.
This document provides instructions for determining the effective size (dimensions) of mini and micro focal spots of industrial X-ray tubes for users in applications where the pin hole method of ISO 32543-1:2024 is not practical. This determination is based on the measurement of profiles of an image of a hole or disk type test objects and the reconstruction of the 2D distribution.
The use of the pin hole method ( ISO 32543-1:2024 ) requires the application of special pin hole cameras. This procedure describes, how the 2D spot shape and size of focal spots can be determined from hole or disk exposures, which are easier to produce in comparison to pin holes and the related cameras.
Microfocus (1 µm ≤ spot sizes < 0,1 mm) and nanofocus tubes (spot sizes < 1 µm) have a significantly lower photon flux than mini and macro focus tubes (spot sizes ≥ 0,1 mm). Furthermore, pin holes (see ISO 32543-1:2024 ) with diameters in the nm and µm region are difficult to manufacture and will not permit sufficient photon statistics for digital imaging with the required magnifications. Nano- and micrometre pin hole methods would require very long exposure times for obtaining a sufficient SNR and CNR.
As an alternative to ISO 32543-1:2024, ASTM E 1165 can also be used.