The invention relates to an arrangement for optically determining the
distance of a reflecting surface that can be used, in particular, for
determining slight variations in distance such as can frequently occur in
vibrating systems. Such an arrangement can also be used as optical
microphone or hydrophone. The arrangement according to the invention is
designed in this case such that light from a light source is directed
onto a reflecting surface via a first optical fiber, and light reflected
therefrom is directed onto at least one statically arranged optical
detector via the first optical fiber or at least one further optical
fiber. An optical element collimating in the direction of the reflecting
surface is arranged between the reflecting surface and the one or more
optical fibers. Furthermore, at least two optical elements focusing in
the direction of the reflecting surface and whose optical axes are
aligned parallel to the optical axis of the collimating optical element
and are arranged at constant spacings from one another are arranged above
the reflecting surface.