Abstract

The use of a novel two-frequency laser in heterodyne interferometry is proposed. In a heterodyne interferometer two beams of different frequencies have to be generated in order to achieve a directional discrimination of a target movement. The different frequency can be generated by the use of an external frequency shifter, in general a Bragg cell. In order to avoid this additional element a two-frequency laser has to be used. Up to now the Zeeman laser and the two mode He-Ne laser have been used. However, the frequency difference of the Zeeman laser is limited to 2 MHz and both lasers have great amplitude and frequency control efforts.

© 1994 IEEE