The long-distance measurement laboratory is capable of accurately measuring distances up to 27 m. The measurement system is based on a heterodyne interferometer, whose movable arm consists of a retro-reflector mounted on a carriage that can move along a guide.

The system can operate in two modes: 

1. A first mode, based on fringe counting for low speeds and with an uncertainty of the order of 0.2 μm at maximum distance; 

2. A second mode, based on the Doppler effect and suitable for high speeds with an uncertainty of the order of 1.5 μm at maximum distance.

The system can be used both for the calibration of commercial laser distance meters and for the calibration or characterisation of absolute telemeters and interferometers.

Milena Astrua