Co-ordinate measuring machine testing. Close-up of the probe head of a coordinate measurement machine (CMM), a system capable of accurate 3D measurements of complex, precision-engineered components. Such machines typically use an optical probe. This is a Hyper Quick Vision (QV) vision co-ordinate measuring machine (VCMM), being used with an optical dimensional artefact (lower centre). This is a standard device used to test and calibrate such machines. Photographed in 2014, at the National Physical Laboratory, Teddington, UK.