Scale correction in submicron computed tomography with a submillimeter field of view

Advances in micro-manufacturing and materials science create a demand for dimensional measurements using computed tomography with sub-micrometer resolution (submicron CT). Correction of the scale of CT data is essential for this task, but existing tools, which are used in CT modalities with lower resolutions, are often not suitable for submicron CT. The following study adapts scale correction to submicron CT using a miniature reference object with two ruby balls, which fits into a field of view with a sub-millimeter diameter and features a calibrated ball center-to-center distance of approximately 450 μm. CT data of the reference object were analyzed to determine a scale correction factor, which was applied to measurements of two additional reference objects of a similar scale and composition. The average bias of measurements for one of the objects was reduced from 3.35 μm to 0.26 μm, and the measurement uncertainty was lowered from 3.4 μm to 1.2 μm. Similar results were also achieved for the second object. The extended scan time of the reference object and the potential for sample drift, which are both typical for submicron CT, were mitigated by angular undersampling. Finally, a complementary scale correction approach is demonstrated using projection data of the reference object. This approach avoids tomographic artifacts caused by very radio-opaque objects, and it is practical for applications that utilize lower-energy X-rays.