Apparatus and method for measuring a sample

Abstract

An apparatus and a method are used for measuring a sample. The apparatus includes a crystal having at least one face in direct contact with the sample, at least one light source emitting and directing at least a first light beam and a second light beam into the same crystal such that the first light beam and the second light beam are totally internally reflected at the interface between the crystal and the sample, and at least one detector detecting the first light beam and the second light beam which have been totally internally reflected at the interface. The first light beam travels along a first optical path in the crystal and the second light beam travels along a second optical path in the crystal, and the first optical path is different from the second optical path in optical property.

Dependencies are inferred from the claim text.