Circuit board quality control calibrator. Physicist adjusting a calibrating machine that uses an X-Y (two-dimensional) optical position standard. The X-Y standard (centre) is a flat plate made from glass or quartz that has a reflective chromium-coated pattern of many crosshairs spanning its surface. These crosshairs are designed to calibrate measuring machines that use a viewing system to locate features. Such machines are used in the automated optical inspection (AOI) of circuit boards, where a camera autonomously scans the boards for faults such as missing components. Photographed at the National Physical Laboratory in Teddington, UK.