Interferometer for absolute distance measurement

An interferometer for absolute distance measurement utilises two lasers 1 and 2, of which at least one has a variable frequency. A coupler 3 combines the beams which are transmitted to a single acousto-optical modulator (AOM) 4 for splitting into partial beams of different frequencies. A beam splitter 5 divides the beams which are then passed to reference and measuring interferometers, 10 and 12 respectively. The interferometer units both consist of beam splitters 13, 14 and polarisation elements 15. The measuring interferometer includes a measuring reflector 11 in its measuring path. Interference signals from both interferometers are converted into electrical signals by a common conversion and evaluation unit 18. Transmitting elements such as optical fibres 6, 7, 8, 9 & 17 between the various components of the arrangement are used, ensuring identical beam geometry for all superimposed beams.