In coordinate measuring technology with computed tomography, the dimensional analysis of work pieces made of  multiple materials is particularly challenging.  Multi-material work pieces are often metal and plastic components, such as assembled plug connectors.  The measurement task is typically to determine the position and bend angle of the internal metal pins.  In a CT measurement, however, the metal pins often cause beam hardening and scattering artifacts.  Historically these effects made the measurement of the plastic enclosure much more difficult.  With Dual-Spectra CT, the measurement software computationally combines two CT measurements into a single volume.

The radiation spectra are tuned to the material combination.  It is then possible to check dimensions in any desired cross section of the volume, for example using 2D contour image processing.  The volume can also be used to derive a single 3D point cloud for the entire work piece.  By reducing the artifacts in the volume, dimensions measured between the different materials have lower measurement uncertainty and sometimes the measurement becomes possible at all.  For work pieces made of a single material with very different radiographic lengths, Multi-Power Tomography is also used.  Two measurements with high and low tube power at the same cathode voltage are linked.

Seen in image above: Dual Spectra Tomography: a, b) Section through a volume with many artifacts after tomography with high and low cathode voltage c) Section through low artifact volume after combination of a, b). d) 3D view of the low-artifact volume (material type highlighted in color)