(Nikon Metrology: Brighton, MI) -- Metrology CT is the fusion of metrology and X-ray computed tomography (CT). X-ray has long been used for industrial applications. With X-ray CT, a number of 2-D X-ray images are taken at different angles around the sample. All the external and internal geometry are captured as the X-rays pass through the sample. Computed tomography software constructs a 3-D model of the sample using these 2-D images. Dimensional characteristics such as size, position, and form can be measured directly using the model as well as full, part-to-CAD comparison, section reporting, and geometric dimensioning and tolerancing (GD&T) analysis.

Nikon’s MCT225 is precalibrated using accuracy standards traceable to the National Physical Laboratory (NPL), the United Kingdom’s national measurement institute and verified using VDI/VDE 2630—“Guidelines for computed tomography in dimensional measurement.” Absolute accuracy guarantees measurement accuracy without time-consuming comparative scans or reference measurements; samples are simply placed on a rotary table inside the enclosure and measured.

A key component of the MCT225 system is the 225 kV micro-focus X-ray source developed in-house by Nikon Metrology. It produces incredibly sharp images with low noise levels, enabling magnification levels up to 150X with 2 µm feature detection.

High-precision linear guideways equipped with high-resolution optical encoders are error-corrected using the laser interferometer mapping techniques employed for coordinate measuring machines (CMMs). For optimal accuracy and long-term stability, finite element analysis (FEA) was used during the design phase to optimize the stiffness of the manipulator.

To minimize thermal effects, the interior of the MCT225 enclosure is temperature controlled, effectively creating an air-conditioned measurement room stable to 20°C ± 1°C.