A first light source emits a light signal along a measurement optical path that includes a sample and a second light source emits a light signal along a dummy measurement optical path. A measurement circuit receives the light signals and provides outputs separated in time which are indicative of the...http://www.google.de/patents/US7884338?utm_source=gb-gplus-sharePatent US7884338 - Method and apparatus for measuring the phase shift induced in a light signal by a sample
