Interferometer with noise reduction system

摘要

An optical interferometer wherein laser noise is reduced or removed by providing an additional optical path (15) in which the noise present can be ascertained and then subtracted from the measurement signal, also containing noise, such that the output signal has an improved signal to noise ratio. The noise may be identified using a-reference interferometer and both the measurement and noise signals may be appropriately processed (11, 24) and filtered (26, 28) before the subtraction stage (30). The system may also be adaptable to other forms of electromagnetic radiation.