The Moore measuring machine in use at INRiM is a 1D comparator equipped with laser interferometers for X axis and precise linear encoders for absolute length measurements for Y and Z axis. The measuring apparatus is made of an interferometric set-up based on plane-mirror differential interferometry. Two mirrors, acting as reference mirrors of a double-pass plane-mirror interferometer, are fixed to the z-stage moving up/down the mechanical probe. The supporting structure is designed for mounting the two mirrors symmetrically and in plane with the mechanical probe, compensating the overall material thermal drifts and then mechanical deformations along the x axis. Due to the symmetric design, the measuring and reference beam paths fulfil the Abbe condition in lateral and vertical alignment when probing the middle height section of the gauge.
In the present set-up the measuring machine may accommodate diameter gauges, up to 200 mm lateral size and about 100 mm height, and linear artefacts up to 420 mm length.