Velocity interferometer with continuously variable sensitivity

Claim 1

A velocity interferometer for determining the time evolution of the velocity of an optically reflecting or back scattering surface and which comprises: a monochromatic, time-coherent light source, arranged so as to transmit a light beam onto the surface to be studied, a light beam splitting means arranged so as to receive the light thrown back by the surface, while transmitting one part thereof and reflecting the other part, a first light reflection means for receiving the part reflected by the splitting means and for reflecting it in the direction of the latter, so that it transmits part thereof, a second light reflection means for receiving the part transmitted by the splitting means and for reflecting it in the direction of the latter, in order that it reflects part thereof, so as to bring about interference between the transmitted part of the light reflected by the first reflection means and the reflected part of the light reflected by the second reflection means, means for detecting the interferences resulting therefrom, and a medium with parallel faces located on the path of the light propagated between the splitting means and one of the reflection means and which serves to delay said light with respect to the light propagating between the splitting means and the other reflection means, the latter being made to coincide with the image of the reflection means associated with said medium, given by the latter and the splitting means, wherein the medium with parallel faces is realized with the aid of a fluid in which said reflection means associated with the medium is immersed and displaceable in translation parallel to the path of the light falling thereon and coming from the splitting means and wherein said other reflection means is displaceable in translation parallel to the path of the light falling thereon and coming from the splitting means.