This invention concerns a heterodyne interferometer for measuring the amplitude of vibration of a vibrating object. The invention is particularly useful for measuring the amplitude of vibrations of objects having reflectivities below about 0.02% or for measuring vibrations amplitudes below about 10.sup.-17...http://www.google.fr/patents/US4834111?utm_source=gb-gplus-shareBrevet US4834111 - Heterodyne interferometer
